def test_lobpcg(matrices):
A_dense, A_sparse, x = matrices
X = x[:, None]
w_dense, v_dense = splin.lobpcg(A_dense, X)
w, v = splin.lobpcg(A_sparse, X)
assert_allclose(w, w_dense)
assert_allclose(v, v_dense)
def laplacian_eigen(image,
seeds=None,
n_components=3,
beta=1,
divide_by_std=False, offsets=((0, 1), (1, 0))):
"""
input : edges image 1 x C x H x W
output: instances probability shape: C x H x W
"""
# Pytorch Tensors to numpy
graph = make2d_lattice_graph(size=(image.shape[0],
image.shape[1]), offsets=offsets)
edges = image2edge_weights(image, graph, beta, divide_by_std=divide_by_std)
A = graph2adjacency(graph, edges)
L = adjacency2laplacian(A, mode=0)
Lu, _ = lap2lapu_bt(L, seeds)
ml = pyamg.ruge_stuben_solver(csr_matrix(Lu))
M = ml.aspreconditioner(cycle='V')
ex = np.random.rand(Lu.shape[0], n_components + 1).astype(np.float32)
eigen_values, eigen_vectors = lobpcg(Lu, ex, largest=False, M=M, tol=1e-8)
#eigen_values, eigen_vectors = lobpcg(Lu, ex, largest=False, tol=1e-8)
eigen_values, eigen_vectors = eigen_values[1:], eigen_vectors[:, 1:]
eigen_vectors = pu_fill(eigen_vectors, seeds)
return eigen_values, eigen_vectors.reshape(image.shape[0],
image.shape[1],
-1)
def locally_linear_embedding(X, n_neighbors, out_dim, tol=1e-6, max_iter=200):
#W = neighbors.kneighbors_graph(
# X, n_neighbors=n_neighbors, mode='distance')
W = barycenter_kneighbors_graph(X, n_neighbors)
print(W)
# M = (I-W)' (I-W)
A = eye(*W.shape, format=W.format) - W
A = (A.T).dot(A).tocsr()
# initial approximation to the eigenvectors
X = np.random.rand(W.shape[0], out_dim)
ml = smoothed_aggregation_solver(A, symmetry='symmetric')
prec = ml.aspreconditioner()
# compute eigenvalues and eigenvectors with LOBPCG
eigen_values, eigen_vectors = linalg.lobpcg(A,
X,
M=prec,
largest=False,
tol=tol,
maxiter=max_iter)
index = np.argsort(eigen_values)
return eigen_vectors[:, index], np.sum(eigen_values)
def bench_lobpcg_mikota():
print()
print(' lobpcg benchmark using mikota pairs')
print('==============================================================')
print(' shape | blocksize | operation | time ')
print(' | (seconds)')
print('--------------------------------------------------------------')
fmt = ' %15s | %3d | %6s | %6.2f '
m = 10
for n in 128, 256, 512, 1024, 2048:
shape = (n, n)
A, B = _mikota_pair(n)
desired_evs = np.square(np.arange(1, m + 1))
tt = time.clock()
X = rand(n, m)
X = orth(X)
LorU, lower = cho_factor(A, lower=0, overwrite_a=0)
M = LinearOperator(shape,
matvec=partial(_precond, LorU, lower),
matmat=partial(_precond, LorU, lower))
eigs, vecs = lobpcg(A, X, B, M, tol=1e-4, maxiter=40)
eigs = sorted(eigs)
elapsed = time.clock() - tt
assert_allclose(eigs, desired_evs)
print(fmt % (shape, m, 'lobpcg', elapsed))
tt = time.clock()
w = eigh(A, B, eigvals_only=True, eigvals=(0, m - 1))
elapsed = time.clock() - tt
assert_allclose(w, desired_evs)
print(fmt % (shape, m, 'eigh', elapsed))
def bench_lobpcg_mikota():
print()
print(' lobpcg benchmark using mikota pairs')
print('==============================================================')
print(' shape | blocksize | operation | time ')
print(' | (seconds)')
print('--------------------------------------------------------------')
fmt = ' %15s | %3d | %6s | %6.2f '
m = 10
for n in 128, 256, 512, 1024, 2048:
shape = (n, n)
A, B = _mikota_pair(n)
desired_evs = np.square(np.arange(1, m+1))
tt = time.clock()
X = rand(n, m)
X = orth(X)
LorU, lower = cho_factor(A, lower=0, overwrite_a=0)
M = LinearOperator(shape,
matvec=partial(_precond, LorU, lower),
matmat=partial(_precond, LorU, lower))
eigs, vecs = lobpcg(A, X, B, M, tol=1e-4, maxiter=40)
eigs = sorted(eigs)
elapsed = time.clock() - tt
assert_allclose(eigs, desired_evs)
print(fmt % (shape, m, 'lobpcg', elapsed))
tt = time.clock()
w = eigh(A, B, eigvals_only=True, eigvals=(0, m-1))
elapsed = time.clock() - tt
assert_allclose(w, desired_evs)
print(fmt % (shape, m, 'eigh', elapsed))
def bench_lobpcg_sakurai():
print()
print(' lobpcg benchmark sakurai et al.')
print('==============================================================')
print(' shape | blocksize | operation | time ')
print(' | (seconds)')
print('--------------------------------------------------------------')
fmt = ' %15s | %3d | %6s | %6.2f '
m = 3
for n in 50, 400, 2400:
shape = (n, n)
A, B, all_eigenvalues = _sakurai(n)
desired_evs = all_eigenvalues[:m]
tt = time.clock()
X = rand(n, m)
eigs, vecs, resnh = lobpcg(A, X, B, tol=1e-6, maxiter=500,
retResidualNormsHistory=1)
w_lobpcg = sorted(eigs)
elapsed = time.clock() - tt
yield (assert_allclose, w_lobpcg, desired_evs, 1e-7, 1e-5)
print(fmt % (shape, m, 'lobpcg', elapsed))
tt = time.clock()
A_dense = A.A
B_dense = B.A
w_eigh = eigh(A_dense, B_dense, eigvals_only=True, eigvals=(0, m-1))
elapsed = time.clock() - tt
yield (assert_allclose, w_eigh, desired_evs, 1e-7, 1e-5)
print(fmt % (shape, m, 'eigh', elapsed))
def eigsys(self, hamiltonian: Hamiltonian,
k: int) -> Tuple[np.ndarray, np.ndarray]:
h_mat = hamiltonian.hamiltonian_matrix()
if self.method == 'eigsh':
eig, vec = eigsh(
h_mat, k=k, which='LM', sigma=0
) # use shift-invert to find smallest eigenvalues quickly
elif self.method == 'lobpcg':
# preconditioning matrix should approximate the inverse of the hamiltonian
# we naively construct this by taking the inverse of diagonal elements
# and setting all others to zero. This is called the Jacobi or diagonal preconditioner.
A = diags([1 / h_mat.diagonal()], [0],
dtype=hamiltonian.space.dtype).tocsc()
precond = lambda x: A @ x
M = LinearOperator(h_mat.shape,
matvec=precond,
matmat=precond,
dtype=hamiltonian.space.dtype)
# guess for eigenvectors is also computed from random numbers
X_approx = np.random.rand(np.prod(hamiltonian.space.grid), k)
sol = lobpcg(h_mat, X_approx, largest=False, M=M, tol=1e-15)
eig, vec = sol[0], sol[1]
else:
raise NotImplementedError(
f"{self.method} solver has not been implemented. Use one of {self.implemented_solvers}"
)
return eig, vec.T
def find_fiedler(L, x, normalized, tol, seed):
L = csc_matrix(L, dtype=float)
n = L.shape[0]
if normalized:
D = spdiags(1.0 / sqrt(L.diagonal()), [0], n, n, format="csc")
L = D * L * D
if method == "lanczos" or n < 10:
# Avoid LOBPCG when n < 10 due to
# https://github.com/scipy/scipy/issues/3592
# https://github.com/scipy/scipy/pull/3594
sigma, X = eigsh(L,
2,
which="SM",
tol=tol,
return_eigenvectors=True)
return sigma[1], X[:, 1]
else:
X = asarray(asmatrix(x).T)
M = spdiags(1.0 / L.diagonal(), [0], n, n)
Y = ones(n)
if normalized:
Y /= D.diagonal()
sigma, X = lobpcg(L,
X,
M=M,
Y=asmatrix(Y).T,
tol=tol,
maxiter=n,
largest=False)
return sigma[0], X[:, 0]
def spectral_clustering(road_map=None, a=None, use_ncut=False, num_clusters=2):
print("Building adjacency matrix")
if(a==None):
a = build_adjacency_matrix(road_map)
print("Computing laplacian")
l = build_laplacian(a, normalize=use_ncut)
print("Spectral embedding")
#e_vals, e_vects = eigsh(l, k=num_clusters, which='SM', tol=0.01, sigma=2.01)
X = np.random.rand(l.shape[0], num_clusters+1)
e_vals, e_vects = lobpcg(l, X, tol=1e-15,
largest=False, maxiter=2000)
embedded_data = e_vects[:,1:]
print e_vals
print("Clustering")
centroid, label, intertia = k_means(embedded_data, num_clusters)
for i in xrange(len(label)):
road_map.nodes[i].region_id = label[i]
def eig_multi(A, B=None, n_components=2, tol=1E-12, random_state=None):
"""Solves the generalized Eigenvalue problem:
A x = lambda B x using the multigrid method.
Works well with very large matrices but there are some
instabilities sometimes.
"""
random_state = check_random_state(random_state)
# convert matrix A and B to float
A = A.astype(np.float64)
if B is not None:
B = B.astype(np.float64)
# import the solver
ml = smoothed_aggregation_solver(check_array(A, accept_sparse=['csr']))
# preconditioner
M = ml.aspreconditioner()
n_nodes = A.shape[0]
n_find = min(n_nodes, 5 + 2 * n_components)
# initial guess for X
np.random.RandomState(seed=1234)
X = random_state.rand(n_nodes, n_find)
# solve using the lobpcg algorithm
eigVals, eigVecs = lobpcg(A, X, M=M, B=B, tol=tol, largest='False')
sort_order = np.argsort(eigVals)
eigVals = eigVals[sort_order]
eigVecs = eigVecs[:, sort_order]
eigVals = eigVals[:n_components]
eigVecs = eigVecs[:, :n_components]
return eigVals, eigVecs
def time_sakurai(self, n, solver):
m = 3
if solver == 'lobpcg':
X = rand(n, m)
eigs, vecs, resnh = lobpcg(self.A, X, self.B, tol=1e-6, maxiter=500,
retResidualNormsHistory=1)
else:
eigh(self.A_dense, self.B_dense, eigvals_only=True, eigvals=(0, m - 1))
def time_sakurai(self, n, solver):
m = 3
if solver == 'lobpcg':
X = rand(n, m)
eigs, vecs, resnh = lobpcg(self.A, X, self.B, tol=1e-6, maxiter=500,
retResidualNormsHistory=1)
else:
w_eigh = eigh(self.A_dense, self.B_dense, eigvals_only=True, eigvals=(0, m-1))
def gGroundSystem(matH):
'''
This function is just a shorthand for getting the ground state `vecGS` and energy `rEg`
of an input Hamiltonian `matH`.
'''
vecGuess = np.random.rand(matH.shape[0], 1)
rEg, vecGS = slin.lobpcg(matH, vecGuess, maxiter=100, largest=False)
return vecGS.T[0], rEg[0]
def solveEigenspace(x, m=2):
k = numpy.random.uniform(.5, 1.0, (len(neighborhoods), m))
for ix in range(20):
t0 = time.time()
res = lobpcg(x, k, largest=False, maxiter=50)
k = res[1]
return res
def solveEigenspace(x, m = 2): k = numpy.random.uniform(.5, 1.0, (len(neighborhoods),m)) for ix in range(20): t0 = time.time() res = lobpcg(x,k,largest=False,maxiter=50) k = res[1] return res
def test_lobpcg(read_guess=True, tol=1e-5):
X = orth(randn(N, m))
if read_guess:
X = x0
try:
λ, v = lobpcg(A, X, largest=False, M=P, maxiter=100, tol=tol)
assert np.max(np.abs(λref - λ)) < tol
except np.linalg.LinAlgError as e:
print("ERROR: ", str(e))
def time_mikota(self, n, solver):
m = 10
if solver == 'lobpcg':
X = rand(n, m)
X = orth(X)
LorU, lower = cho_factor(self.A, lower=0, overwrite_a=0)
M = LinearOperator(self.shape,
matvec=partial(_precond, LorU, lower),
matmat=partial(_precond, LorU, lower))
eigs, vecs = lobpcg(self.A, X, self.B, M, tol=1e-4, maxiter=40)
else:
w = eigh(self.A, self.B, eigvals_only=True, eigvals=(0, m-1))
def time_mikota(self, n, solver):
m = 10
if solver == 'lobpcg':
X = rand(n, m)
X = orth(X)
LorU, lower = cho_factor(self.A, lower=0, overwrite_a=0)
M = LinearOperator(self.shape,
matvec=partial(_precond, LorU, lower),
matmat=partial(_precond, LorU, lower))
eigs, vecs = lobpcg(self.A, X, self.B, M, tol=1e-4, maxiter=40)
else:
eigh(self.A, self.B, eigvals_only=True, eigvals=(0, m - 1))
def fiedler(adj_list, plot=False, fn="FiedlerPlots", n_fied=2):
"""calculate the first fiedler vector of a graph adjascancy list and optionally write associated plots to file.
Takes:
adj_list:
An Nx2 nested list of ints of the form:
[[node1,node2],
...]
Representing the adjascancy list.
plot=False: make plots or not.
fn="FiedlerPlots": filename to prepend to the plot png file names
n_fied=2: the number of fiedler vectors to calculate (values above 2 will not be output)
Returns a Dictionary of the form:
{"f1": the first fiedler vector,
"f2": (if caclulated) the second fideler vector
"d": the node degrees,
"r1": the rank of each node in the first fiedler vector
"r2": the rank of each node in the second fiedler vector}
"""
A = graph_laplacian(adj_list)
# construct preconditioner
ml = smoothed_aggregation_solver(A, coarse_solver='pinv2', max_coarse=10)
M = ml.aspreconditioner()
# solve for lowest two modes: constant vector and Fiedler vector
X = scipy.rand(A.shape[0], n_fied + 1)
(eval,evec,res) = lobpcg(A, X, M=None, tol=1e-12, largest=False, \
verbosityLevel=0, retResidualNormsHistory=True)
if plot:
doPlots(evec[:, 1], evec[:, 2], A.diagonal(), adj_list, fn)
out = {
"f1": list(evec[:, 1]),
"d": list(A.diagonal()),
"r1": [int(i) for i in list(numpy.argsort(numpy.argsort(evec[:, 1])))]
}
if n_fied > 1:
out["f2"] = list(evec[:, 2])
out["r2"] = [
int(i) for i in list(numpy.argsort(numpy.argsort(evec[:, 2])))
]
return out
def ess(operator, M, k=2):
r"""
An efficient sampling set selection method for bandlimited graph signals [1]_.
Parameters
----------
operator: SparseTensor
The chosen variation operators, e.g., graph normalized Laplacian.
M: int
The number of desired sampled nodes.
k: int
The proxy order. Refer to the literature for details.
Returns
-------
S: list
A list containing sampled nodes with the sampling order
References
----------
.. [1] Aamir Anis, et al., “Efficient sampling set selection for bandlimited graph
signals using graph spectral proxies,” IEEE TSP, 2016.
"""
import scipy.sparse.linalg as splin
# add GPU support after cp.setdiff1d is implemented
# dt, dv, density, on_gpu = get_ddd(operator)
# xp, xcipy, xsplin = get_array_module(on_gpu)
L = to_scipy(operator)
N = L.shape[-1]
LtL = L.T**k * L**k
V = np.arange(N)
S = list()
while len(S) < M:
Sc = np.setdiff1d(V, S)
length = len(Sc)
if length == 1:
S.append(Sc[0])
break
reduced = LtL[np.ix_(Sc, Sc)]
sigma, psi = splin.lobpcg(reduced,
X=np.random.rand(length, 1),
largest=False)
psi = psi.ravel()
v = Sc[np.argmax(np.abs(psi)).item()]
S.append(v)
return S
def solve_on_coarse_level(self):
if comm.rank == 0:
if self.verbosity >= 2:
print pid+" Solving on coarse level"
timer = Timer("Coarse level solution")
if self.problem.switch_matrices_on_coarse_level:
A = self.B_coarse
B = self.A_coarse
largest = True
which = 'LM'
else:
A = self.A_coarse
B = self.B_coarse
largest = False
which = 'SM'
# Set initial approximation
self.v_coarse.fill(0.0)
self.v_coarse[0] = 1.0
if self.use_lobpcg_on_coarse_level:
if self.precond_lobpcg_by_ml:
if self.update_lobpcg_prec or self.M is None:
if self.verbosity >= 3:
print0(pid+" Creating coarse level preconditioner")
ml = smoothed_aggregation_solver(A)
self.M = ml.aspreconditioner()
w, v, h = lobpcg(A, self.v_coarse, B, self.M, tol=self.coarse_level_tol, maxiter=self.coarse_level_maxit,
largest=largest, verbosityLevel=self.lobpcg_verb, retResidualNormsHistory=True)
else:
if self.problem.sym:
w, v = eigsh(A, 1, B, which=which, v0=self.v_coarse,
ncv=self.coarse_level_num_ritz_vec, maxiter=self.coarse_level_maxit, tol=self.coarse_level_tol)
else:
w, v = eigs(A, 1, B, which=which, v0=self.v_coarse,
ncv=self.coarse_level_num_ritz_vec, maxiter=self.coarse_level_maxit, tol=self.coarse_level_tol)
self.lam = w[0]
self.v_coarse = v[0]
try:
self.num_it_coarse += len(h)
except NameError:
pass # There seems to be no way to obtain number of iterations for eigs/eigsh
def iter_cond_number_lobpcg(L, invPL):
k = 20
scipy.random.seed(0)
X = scipy.random.rand(n, k)
# compute the smallest eigenvalues:
min_w_invPL_L, temp = SSLA.lobpcg(L * invPL * invPL * L,
X,
maxiter=20,
tol=1e-3,
largest=False,
verbosityLevel=1)
# compute the largest eigenvalues:
max_w_invPL_L, temp = SSLA.lobpcg(opt.eyelo(n),
X,
B=L * invPL * invPL * L,
maxiter=20,
tol=1e-3,
largest=False,
verbosityLevel=1)
max_w_invPL_L = 1 / max_w_invPL_L
assert (max_w_invPL_L[0] >= min_w_invPL_L[::-1][0]
and min_w_invPL_L[0] <= min_w_invPL_L[::-1][0])
return np.sqrt(max_w_invPL_L[0] / min_w_invPL_L[0])
def fiedler(adj_list,plot=False,fn="FiedlerPlots",n_fied=2):
"""calculate the first fiedler vector of a graph adjascancy list and optionally write associated plots to file.
Takes:
adj_list:
An Nx2 nested list of ints of the form:
[[node1,node2],
...]
Representing the adjascancy list.
plot=False: make plots or not.
fn="FiedlerPlots": filename to prepend to the plot png file names
n_fied=2: the number of fiedler vectors to calculate (values above 2 will not be output)
Returns a Dictionary of the form:
{"f1": the first fiedler vector,
"f2": (if caclulated) the second fideler vector
"d": the node degrees,
"r1": the rank of each node in the first fiedler vector
"r2": the rank of each node in the second fiedler vector}
"""
A = graph_laplacian(adj_list)
# construct preconditioner
ml = smoothed_aggregation_solver(A, coarse_solver='pinv2',max_coarse=10)
M = ml.aspreconditioner()
# solve for lowest two modes: constant vector and Fiedler vector
X = scipy.rand(A.shape[0], n_fied+1)
(eval,evec,res) = lobpcg(A, X, M=None, tol=1e-12, largest=False, \
verbosityLevel=0, retResidualNormsHistory=True)
if plot:
doPlots(evec[:,1],evec[:,2],A.diagonal(),adj_list,fn)
out = {"f1":list(evec[:,1]),"d":list(A.diagonal()),"r1":[int(i) for i in list(numpy.argsort(numpy.argsort(evec[:,1])))]}
if n_fied > 1:
out["f2"]=list(evec[:,2])
out["r2"]=[int(i) for i in list(numpy.argsort(numpy.argsort(evec[:,2])))]
return out
def locally_linear_embedding(X, n_neighbors, out_dim, tol=1e-6, max_iter=200):
W = neighbors.kneighbors_graph(X, n_neighbors=n_neighbors, mode="barycenter")
# M = (I-W)' (I-W)
A = eye(*W.shape, format=W.format) - W
A = (A.T).dot(A).tocsr()
# initial approximation to the eigenvectors
X = np.random.rand(W.shape[0], out_dim)
ml = smoothed_aggregation_solver(A, symmetry="symmetric")
prec = ml.aspreconditioner()
# compute eigenvalues and eigenvectors with LOBPCG
eigen_values, eigen_vectors = linalg.lobpcg(A, X, M=prec, largest=False, tol=tol, maxiter=max_iter)
index = np.argsort(eigen_values)
return eigen_vectors[:, index], np.sum(eigen_values)
def locally_linear_embedding(W, out_dim, i_dim, j_dim, tol=1e-5, max_iter=2000):
# M = (I-W)' (I-W)
A = eye(*W.shape, format=W.format) - W
A = (A.T).dot(A).tocsr()
# initial approximation to the eigenvectors - use coords
X = np.random.rand(W.shape[0], out_dim)
X[:, 1] = np.arange(W.shape[0]) % j_dim
X[:, 0] = (np.arange(W.shape[0], dtype=int) / j_dim) % i_dim
ml = smoothed_aggregation_solver(A, symmetry='symmetric')
prec = ml.aspreconditioner()
# compute eigenvalues and eigenvectors with LOBPCG
eigen_values, eigen_vectors = linalg.lobpcg(
A, X, M=prec, largest=False, tol=tol, maxiter=max_iter)
index = np.argsort(eigen_values)
return eigen_vectors[:, index], np.sum(eigen_values)
def spectral_partition(A):
ml = smoothed_aggregation_solver(A,
coarse_solver='pinv2',max_coarse=100,smooth=None, strength=None)
print ml
M = ml.aspreconditioner()
X = sp.rand(A.shape[0], 2)
(evals,evecs,res) = lobpcg(A, X, M=M, tol=1e-12, largest=False, \
verbosityLevel=0, retResidualNormsHistory=True, maxiter=200)
fiedler = evecs[:,1]
vmed = np.median(fiedler)
v = np.zeros((A.shape[0],))
K = np.where(fiedler<=vmed)[0]
v[K]=-1
K = np.where(fiedler>vmed)[0]
v[K]=1
return v, res
def eigen_solve(A, mode):
"""solve for eigenpairs using a specified method"""
if mode == 'arpack_eigsh':
return arpack.eigsh(A, largest=True, tol=1e-4)
elif mode == 'arpack_eigsh_mkl':
return arpack.eigsh_mkl(A, largest=True, tol_dps=4)
elif mode == 'torch_eigh':
return torch.linalg.eigh(A)
elif mode == 'torch_lobpcg':
return torch.lobpcg(A, k=1, largest=True, tol=1e-4)
elif mode == 'scipy_eigsh':
# For some reason scipy's eigsh requires slightly smaller tolerance
# (1e-5 vs 1e-4) to reach equiavelent accuracy
return splinalg.eigsh(A.numpy(), k=1, which="LA", tol=1e-5)
elif mode == 'scipy_lobpcg':
X = A.new_empty(A.size(0), 1).normal_()
return splinalg.lobpcg(A.numpy(), X.numpy(), largest=True, tol=1e-4)
else:
raise ValueError
def lobpcg_randEVD(A, k, sketching_type, s):
"""
Approximate top k eigenvalue and corresponding right eigenvector computation
for At * A using LOBPCG over preconditioner attained through sketching.
Parameters
----------
A : m x n matrix, expected tall-and-thin (m > n)
k : number of top eignevalues
sketching_type : sketching transformation type (row number reducer)
s : number of rows in the sketched matrix
Returns
--------
lambdas : top k eigenavalues of At * A
Vt : top k right singular vectors At * A (as rows of Vt)
Notes/TODO
-----------
- ordering eigenvalues in lobpcg
- opt out the option of using a generic symmetric eigenvalue solver internally
"""
m, n = A.shape
assert m > n
assert n >= k
if s == None:
s = 4 * n
assert s < m
sketch = sketching_type(m, s)
B = sketch * A
U, Sigma, Vt = linalg.svd(B, full_matrices=False)
Q, R = linalg.qr(B) # alternatively: connection of R to V, Sigma
Aop = symmetrizer(A)
X = Vt[:k, :].T
Rop = upper_triangular_preconditioner_symmetrizer(R)
lambdas, Vt = lobpcg(Aop, X, M=Rop, largest=True)
return lambdas, Vt
def lobpcg_randEVD(A, k, sketching_type, s):
'''
Approximate top k eigenvalue and corresponding right eigenvector computation
for At * A using LOBPCG over preconditioner attained through sketching.
Parameters
----------
A : m x n matrix, expected tall-and-thin (m > n)
k : number of top eignevalues
sketching_type : sketching transformation type (row number reducer)
s : number of rows in the sketched matrix
Returns
--------
lambdas : top k eigenavalues of At * A
Vt : top k right singular vectors At * A (as rows of Vt)
Notes/TODO
-----------
- ordering eigenvalues in lobpcg
- opt out the option of using a generic symmetric eigenvalue solver internally
'''
m, n = A.shape
assert m > n
assert n >= k
if s == None:
s = 4 * n
assert s < m
sketch = sketching_type(m, s)
B = sketch * A
U, Sigma, Vt = linalg.svd(B, full_matrices=False)
Q, R = linalg.qr(B) # alternatively: connection of R to V, Sigma
Aop = symmetrizer(A)
X = Vt[:k, :].T
Rop = upper_triangular_preconditioner_symmetrizer(R)
lambdas, Vt = lobpcg(Aop, X, M=Rop, largest=True)
return lambdas, Vt
def find_fiedler(L, x, normalized, tol):
L = csc_matrix(L, dtype=float)
n = L.shape[0]
if normalized:
D = spdiags(1.0 / sqrt(L.diagonal()), [0], n, n, format="csc")
L = D * L * D
if method == "lanczos" or n < 10:
# Avoid LOBPCG when n < 10 due to
# https://github.com/scipy/scipy/issues/3592
# https://github.com/scipy/scipy/pull/3594
sigma, X = eigsh(L, 2, which="SM", tol=tol, return_eigenvectors=True)
return sigma[1], X[:, 1]
else:
X = asarray(asmatrix(x).T)
M = spdiags(1.0 / L.diagonal(), [0], n, n)
Y = ones(n)
if normalized:
Y /= D.diagonal()
sigma, X = lobpcg(L, X, M=M, Y=asmatrix(Y).T, tol=tol, maxiter=n, largest=False)
return sigma[0], X[:, 0]
def StrongConvexity(loss, output, model, lambda_max=None):
from scipy.sparse.linalg import eigsh
from scipy.sparse.linalg import LinearOperator, lobpcg
# SmoothnessAbsHessian returns the maximum eigenvalue of the absolute Hessian (i.e. the square root of the maximum of the squared Hessian)
if lambda_max is None:
lambda_max = SmoothnessAbsHessian(loss, output, model)
ndim = len(torch.nn.utils.parameters_to_vector(model.parameters()))
batch = output.size(0)
def NumpyWrapper(vp):
vp = vector_to_parameter_list(
torch.tensor(np.squeeze(vp), device='cuda').float(),
model.parameters())
Hv = HessianSqrVectorProduct(loss, list(model.parameters()), vp)
Hv = torch.cat([torch.flatten(v) for v in Hv]) / batch
return Hv.cpu().numpy()
A = LinearOperator((ndim, ndim), matvec=NumpyWrapper)
# use the Lanczos method to estimate the largest Largest (in magnitude) eigenvalue ('LM')
lambda_min, vs = eigsh(A,
1,
which='LM',
return_eigenvectors=1,
tol=1e-2,
sigma=lambda_max**2)
l, v = lobpcg(A,
vs,
B=None,
M=None,
Y=None,
tol=None,
maxiter=50,
largest=False,
verbosityLevel=0,
retLambdaHistory=False,
retResidualNormsHistory=False)
return np.sqrt(l)
def spectral(A, eval=None, evec=None, plot=False, method='lobpcg'):
# solve for lowest two modes: constant vector and Fiedler vector
X = scipy.rand(A.shape[0], 2)
if method == 'lobpcg':
# specify lowest eigenvector and orthonormalize fiedler against it
X[:, 0] = numpy.ones((A.shape[0], ))
X = numpy.linalg.qr(X, mode='full')[0]
# construct preconditioner
ml = smoothed_aggregation_solver(A, coarse_solver='pinv2')
M = ml.aspreconditioner()
(eval,evec,res) = lobpcg(A, X, M=M, tol=1e-5, largest=False, \
verbosityLevel=0, retResidualNormsHistory=True, maxiter=200)
elif method == 'tracemin':
res = []
evec = tracemin_fiedler(A, residuals=res, tol=1e-5)
evec[:, 1] = rqi(A, evec[:, 1], k=3)[1]
else:
raise InputError('Unknown method')
# use the median of fiedler, as the separator
fiedler = evec[:, 1]
vmed = numpy.median(fiedler)
P1 = numpy.where(fiedler <= vmed)[0]
P2 = numpy.where(fiedler > vmed)[0]
if plot is True:
from matplotlib.pyplot import semilogy, figure, show, title, xlabel, ylabel
figure()
semilogy(res)
xlabel('Iteration')
ylabel('Residual norm')
title('Spectral convergence history')
show()
return P1, P2, fiedler
def spectral(A,eval=None,evec=None,plot=False,method='lobpcg') :
# solve for lowest two modes: constant vector and Fiedler vector
X = scipy.rand(A.shape[0], 2)
if method == 'lobpcg' :
# specify lowest eigenvector and orthonormalize fiedler against it
X[:,0] = numpy.ones((A.shape[0],))
X = numpy.linalg.qr(X, mode='full')[0]
# construct preconditioner
ml = smoothed_aggregation_solver(A,coarse_solver='pinv2')
M = ml.aspreconditioner()
(eval,evec,res) = lobpcg(A, X, M=M, tol=1e-5, largest=False, \
verbosityLevel=0, retResidualNormsHistory=True, maxiter=200)
elif method == 'tracemin':
res = []
evec = tracemin_fiedler(A, residuals=res, tol=1e-5)
evec[:,1] = rqi(A, evec[:,1], k=3)[1]
else :
raise InputError('Unknown method')
# use the median of fiedler, as the separator
fiedler = evec[:,1]
vmed = numpy.median(fiedler)
P1 = numpy.where(fiedler<=vmed)[0]
P2 = numpy.where(fiedler>vmed)[0]
if plot is True :
from matplotlib.pyplot import semilogy,figure,show,title,xlabel,ylabel
figure()
semilogy(res)
xlabel('Iteration')
ylabel('Residual norm')
title('Spectral convergence history')
show()
return P1,P2,fiedler
def eig_multi(A, B=None, n_components=2, tol=1E-12, random_state=None):
"""Solves the generalized Eigenvalue problem:
A x = lambda B x using the multigrid method.
Works well with very large matrices but there are some
instabilities sometimes.
"""
random_state = check_random_state(random_state)
# convert matrix A and B to float
A = A.astype(np.float64);
if B is not None:
B = B.astype(np.float64)
# import the solver
ml = smoothed_aggregation_solver(check_array(A, accept_sparse = ['csr']))
# preconditioner
M = ml.aspreconditioner()
n_nodes = A.shape[0]
n_find = min(n_nodes, 5 + 2*n_components)
# initial guess for X
np.random.RandomState(seed=1234)
X = random_state.rand(n_nodes, n_find)
# solve using the lobpcg algorithm
eigVals, eigVecs = lobpcg(A, X, M=M, B=B,
tol=tol,
largest='False')
sort_order = np.argsort(eigVals)
eigVals = eigVals[sort_order]
eigVecs = eigVecs[:, sort_order]
eigVals = eigVals[:n_components]
eigVecs = eigVecs[:, :n_components]
return eigVals, eigVecs
def main_fisher_diag(l, neigs=0):
logging.info('main_fisher - new UbercalModel')
model = UbercalModel(l)
logging.info('building fisher matrix')
model.pars['zps'].fix(0, 0.0)
v, J = model(jac=True)
# J.data /= 0.01**2
N, n = J.shape
H = J.T * J
logging.info('cholesky factorization')
fact = cholmod.cholesky(H)
logging.info('cholesky inverse')
def mv(x):
return fact.solve_A(x)
OPinv = OPinv = linalg.LinearOperator(H.shape, mv)
e, v = None, None
if neigs > 0:
logging.info('extracting smallest eigenvals/eigenvects')
# X = np.random.random((n,3))
X = np.random.random(neigs * 5288154)
X = X = X.reshape((-1, neigs))
tol = 1.E-5
e, v = linalg.lobpcg(H,
X,
largest=False,
verbosityLevel=2,
maxiter=100,
M=OPinv)
return H, e, v, model, fact
def bench_lobpcg_sakurai():
print()
print(' lobpcg benchmark sakurai et al.')
print('==============================================================')
print(' shape | blocksize | operation | time ')
print(' | (seconds)')
print('--------------------------------------------------------------')
fmt = ' %15s | %3d | %6s | %6.2f '
m = 3
for n in 50, 400, 2400:
shape = (n, n)
A, B, all_eigenvalues = _sakurai(n)
desired_evs = all_eigenvalues[:m]
tt = time.clock()
X = rand(n, m)
eigs, vecs, resnh = lobpcg(A,
X,
B,
tol=1e-6,
maxiter=500,
retResidualNormsHistory=1)
w_lobpcg = sorted(eigs)
elapsed = time.clock() - tt
yield (assert_allclose, w_lobpcg, desired_evs, 1e-7, 1e-5)
print(fmt % (shape, m, 'lobpcg', elapsed))
tt = time.clock()
A_dense = A.A
B_dense = B.A
w_eigh = eigh(A_dense, B_dense, eigvals_only=True, eigvals=(0, m - 1))
elapsed = time.clock() - tt
yield (assert_allclose, w_eigh, desired_evs, 1e-7, 1e-5)
print(fmt % (shape, m, 'eigh', elapsed))
def eigen_decomposition(G, n_components=8, eigen_solver=None,
random_state=None, eigen_tol=0.0,
drop_first=True, largest = True):
"""
G : 2d numpy/scipy array. Potentially sparse.
The matrix to find the eigendecomposition of
n_components : integer, optional
The number of eigenvectors to return
eigen_solver : {'auto', 'dense', 'arpack', 'lobpcg', or 'amg'}
auto : algorithm will attempt to choose the best method for input data
dense : use standard dense matrix operations for the eigenvalue
decomposition. For this method, M must be an array
or matrix type. This method should be avoided for
large problems.
arpack : use arnoldi iteration in shift-invert mode.
For this method, M may be a dense matrix, sparse matrix,
or general linear operator.
Warning: ARPACK can be unstable for some problems. It is
best to try several random seeds in order to check results.
lobpcg : Locally Optimal Block Preconditioned Conjugate Gradient Method.
a preconditioned eigensolver for large symmetric positive definite
(SPD) generalized eigenproblems.
amg : AMG requires pyamg to be installed. It can be faster on very large,
sparse problems, but may also lead to instabilities.
random_state : int seed, RandomState instance, or None (default)
A pseudo random number generator used for the initialization of the
lobpcg eigen vectors decomposition when eigen_solver == 'amg'.
By default, arpack is used.
eigen_tol : float, optional, default=0.0
Stopping criterion for eigendecomposition when using arpack eigen_solver
Returns
-------
lambdas, diffusion_map : eigenvalues, eigenvectors
"""
n_nodes = G.shape[0]
if eigen_solver is None:
eigen_solver = 'auto'
elif not eigen_solver in eigen_solvers:
raise ValueError("Unknown value for eigen_solver: '%s'."
"Should be: '%s'"
% eigen_solver, eigen_solvers)
if eigen_solver == 'auto':
if G.shape[0] > 200:
eigen_solver = 'arpack'
else:
eigen_solver = 'dense'
# Check eigen_solver method
try:
from pyamg import smoothed_aggregation_solver
except ImportError:
if eigen_solver == "amg":
raise ValueError("The eigen_solver was set to 'amg', but pyamg is "
"not available.")
# Check input values
if not isinstance(largest, bool):
raise ValueError("largest should be True if you want largest eigenvalues otherwise False")
random_state = check_random_state(random_state)
if drop_first:
n_components = n_components + 1
# Check for symmetry
is_symmetric = _is_symmetric(G)
# Convert G to best type for eigendecomposition
if sparse.issparse(G):
if G.getformat() is not 'csr':
G.tocsr()
G = G.astype(np.float)
if ((eigen_solver == 'lobpcg') and (n_nodes < 5 * n_components + 1)):
warnings.warn("lobpcg has problems with small number of nodes. Using dense eigh")
eigen_solver = 'dense'
# Try Eigen Methods:
if eigen_solver == 'arpack':
if is_symmetric:
if largest:
which = 'LM'
else:
which = 'SM'
lambdas, diffusion_map = eigsh(G, k=n_components, which=which,tol=eigen_tol)
else:
if largest:
which = 'LR'
else:
which = 'SR'
lambdas, diffusion_map = eigs(G, k=n_components, which=which,tol=eigen_tol)
lambdas = np.real(lambdas)
diffusion_map = np.real(diffusion_map)
elif eigen_solver == 'amg':
if not is_symmetric:
raise ValueError("lobpcg requires symmetric matrices.")
if not sparse.issparse(G):
warnings.warn("AMG works better for sparse matrices")
# Use AMG to get a preconditioner and speed up the eigenvalue problem.
ml = smoothed_aggregation_solver(check_array(G, accept_sparse = ['csr']))
M = ml.aspreconditioner()
n_find = min(n_nodes, 5 + 2*n_components)
X = random_state.rand(n_nodes, n_find)
X[:, 0] = (G.diagonal()).ravel()
lambdas, diffusion_map = lobpcg(G, X, M=M, largest=largest)
sort_order = np.argsort(lambdas)
if largest:
lambdas = lambdas[sort_order[::-1]]
diffusion_map = diffusion_map[:, sort_order[::-1]]
else:
lambdas = lambdas[sort_order]
diffusion_map = diffusion_map[:, sort_order]
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == "lobpcg":
if not is_symmetric:
raise ValueError("lobpcg requires symmetric matrices.")
n_find = min(n_nodes, 5 + 2*n_components)
X = random_state.rand(n_nodes, n_find)
lambdas, diffusion_map = lobpcg(G, X, largest=largest)
sort_order = np.argsort(lambdas)
if largest:
lambdas = lambdas[sort_order[::-1]]
diffusion_map = diffusion_map[:, sort_order[::-1]]
else:
lambdas = lambdas[sort_order]
diffusion_map = diffusion_map[:, sort_order]
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == 'dense':
if sparse.isspmatrix(G):
G = G.todense()
if is_symmetric:
lambdas, diffusion_map = eigh(G)
else:
lambdas, diffusion_map = eig(G)
if largest:# eigh always returns eigenvalues in ascending order
lambdas = lambdas[::-1] # reverse order the e-values
diffusion_map = diffusion_map[:, ::-1] # reverse order the vectors
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
return (lambdas, diffusion_map)
def eigs_lobpcg(A,
k,
*,
B=None,
v0=None,
which=None,
return_vecs=True,
sigma=None,
isherm=True,
P=None,
sort=True,
**lobpcg_opts):
"""Interface to scipy's lobpcg eigensolver, which can be good for
generalized eigenproblems with matrix-free operators. Seems to a be a bit
innacurate though (e.g. on the order of ~ 1e-6 for eigenvalues). Also only
takes real, symmetric problems, targeting smallest eigenvalues (though
scipy will soon have complex support, and its easy to add oneself).
Note that the slepc eigensolver also has a lobpcg backend
(``EPSType='lobpcg'``) which accepts complex input and is more accurate -
though seems slower.
Parameters
----------
A : array_like, sparse_matrix, LinearOperator or callable
The operator to solve for.
k : int
Number of eigenpairs to return
B : array_like, sparse_matrix, LinearOperator or callable, optional
If given, the RHS operator (which should be positive) defining a
generalized eigen problem.
v0 : array_like (d, k), optional
The initial subspace to iterate with.
which : {'SA', 'LA'}, optional
Find the smallest or largest eigenvalues.
return_vecs : bool, optional
Whether to return the eigenvectors found.
P : array_like, sparse_matrix, LinearOperator or callable, optional
Perform the eigensolve in the subspace defined by this projector.
sort : bool, optional
Whether to ensure the eigenvalues are sorted in ascending value.
lobpcg_opts
Supplied to :func:`scipy.sparse.linagl.lobpcg`.
Returns
-------
lk : array_like (k,)
The eigenvalues.
vk : array_like (d, k)
The eigenvectors, if `return_vecs=True`.
See Also
--------
eigs_scipy, eigs_numpy, eigs_slepc
"""
if not isherm:
raise ValueError("lobpcg can only solve symmetric problems.")
if sigma is not None:
raise ValueError("lobpcg can only solve extremal eigenvalues.")
# remove invalid options for lobpcg
lobpcg_opts.pop('ncv', None)
lobpcg_opts.pop('EPSType', None)
# convert some arguments and defaults
lobpcg_opts.setdefault('maxiter', 30)
if lobpcg_opts['maxiter'] is None:
lobpcg_opts['maxiter'] = 30
largest = {'SA': False, 'LA': True}[which]
if isinstance(A, qu.Lazy):
A = A()
if isinstance(B, qu.Lazy):
B = B()
if isinstance(P, qu.Lazy):
P = P()
# project into subspace
if P is not None:
A = qu.dag(P) @ (A @ P)
# avoid matrix like behaviour
if isinstance(A, qu.qarray):
A = A.A
d = A.shape[0]
# set up the initial subsspace to iterate with
if v0 is None:
v0 = qu.randn((d, k), dtype=A.dtype)
else:
# check if intial space should be projected too
if P is not None and v0.shape[0] != d:
v0 = qu.dag(P) @ v0
v0 = v0.reshape(d, -1)
# if not enough initial states given, flesh out with random
if v0.shape[1] != k:
v0 = np.hstack(v0, qu.randn((d, k - v0.shape[1]), dtype=A.dtype))
lk, vk = spla.lobpcg(A=A, X=v0, B=B, largest=largest, **lobpcg_opts)
if return_vecs:
vk = qu.qarray(vk)
return maybe_sort_and_project(lk, vk, P, sort)
else:
return np.sort(lk) if sort else lk
# this is the only reliable solver.
if run_slp:
k = top_k
# initial approximation to the k eigenvectors
if not pre:
scipy.random.seed(0)
X = scipy.random.uniform(-1, 1, size=(L.shape[0], k))
else:
X = pre.v_L
largest = False
w_L, v_L = SSLA.lobpcg(L,
X,
B=M,
M=invPL,
maxiter=10,
tol=1e-8,
largest=largest,
verbosityLevel=1)
if largest:
w_L = w_L[::-1]
v_L = v_L[:, ::-1]
w_L = 1 / w_L
plt.figure()
plt.plot(range(k), w_L)
if verify_dense:
plt.plot(range(k), w_dL[range(k)])
# show_mesh(V,F,v_L[:,0])
output.w_L = w_L
def spectral_embedding(adjacency, n_components=8, eigen_solver=None,
random_state=None, eigen_tol=0.0,
norm_laplacian=True, drop_first=True):
"""Project the sample on the first eigenvectors of the graph Laplacian.
The adjacency matrix is used to compute a normalized graph Laplacian
whose spectrum (especially the eigenvectors associated to the
smallest eigenvalues) has an interpretation in terms of minimal
number of cuts necessary to split the graph into comparably sized
components.
This embedding can also 'work' even if the ``adjacency`` variable is
not strictly the adjacency matrix of a graph but more generally
an affinity or similarity matrix between samples (for instance the
heat kernel of a euclidean distance matrix or a k-NN matrix).
However care must taken to always make the affinity matrix symmetric
so that the eigenvector decomposition works as expected.
Note : Laplacian Eigenmaps is the actual algorithm implemented here.
Read more in the :ref:`User Guide <spectral_embedding>`.
Parameters
----------
adjacency : array-like or sparse matrix, shape: (n_samples, n_samples)
The adjacency matrix of the graph to embed.
n_components : integer, optional, default 8
The dimension of the projection subspace.
eigen_solver : {None, 'arpack', 'lobpcg', or 'amg'}, default None
The eigenvalue decomposition strategy to use. AMG requires pyamg
to be installed. It can be faster on very large, sparse problems,
but may also lead to instabilities.
random_state : int, RandomState instance or None, optional, default: None
A pseudo random number generator used for the initialization of the
lobpcg eigenvectors decomposition. If int, random_state is the seed
used by the random number generator; If RandomState instance,
random_state is the random number generator; If None, the random number
generator is the RandomState instance used by `np.random`. Used when
``solver`` == 'amg'.
eigen_tol : float, optional, default=0.0
Stopping criterion for eigendecomposition of the Laplacian matrix
when using arpack eigen_solver.
norm_laplacian : bool, optional, default=True
If True, then compute normalized Laplacian.
drop_first : bool, optional, default=True
Whether to drop the first eigenvector. For spectral embedding, this
should be True as the first eigenvector should be constant vector for
connected graph, but for spectral clustering, this should be kept as
False to retain the first eigenvector.
Returns
-------
embedding : array, shape=(n_samples, n_components)
The reduced samples.
Notes
-----
Spectral Embedding (Laplacian Eigenmaps) is most useful when the graph
has one connected component. If there graph has many components, the first
few eigenvectors will simply uncover the connected components of the graph.
References
----------
* https://en.wikipedia.org/wiki/LOBPCG
* Toward the Optimal Preconditioned Eigensolver: Locally Optimal
Block Preconditioned Conjugate Gradient Method
Andrew V. Knyazev
http://dx.doi.org/10.1137%2FS1064827500366124
"""
adjacency = check_symmetric(adjacency)
try:
from pyamg import smoothed_aggregation_solver
except ImportError:
if eigen_solver == "amg":
raise ValueError("The eigen_solver was set to 'amg', but pyamg is "
"not available.")
if eigen_solver is None:
eigen_solver = 'arpack'
elif eigen_solver not in ('arpack', 'lobpcg', 'amg'):
raise ValueError("Unknown value for eigen_solver: '%s'."
"Should be 'amg', 'arpack', or 'lobpcg'"
% eigen_solver)
random_state = check_random_state(random_state)
n_nodes = adjacency.shape[0]
# Whether to drop the first eigenvector
if drop_first:
n_components = n_components + 1
if not _graph_is_connected(adjacency):
warnings.warn("Graph is not fully connected, spectral embedding"
" may not work as expected.")
laplacian, dd = sparse.csgraph.laplacian(adjacency, normed=norm_laplacian,
return_diag=True)
if (eigen_solver == 'arpack' or eigen_solver != 'lobpcg' and
(not sparse.isspmatrix(laplacian) or n_nodes < 5 * n_components)):
# lobpcg used with eigen_solver='amg' has bugs for low number of nodes
# for details see the source code in scipy:
# https://github.com/scipy/scipy/blob/v0.11.0/scipy/sparse/linalg/eigen
# /lobpcg/lobpcg.py#L237
# or matlab:
# http://www.mathworks.com/matlabcentral/fileexchange/48-lobpcg-m
laplacian = _set_diag(laplacian, 1, norm_laplacian)
# Here we'll use shift-invert mode for fast eigenvalues
# (see http://docs.scipy.org/doc/scipy/reference/tutorial/arpack.html
# for a short explanation of what this means)
# Because the normalized Laplacian has eigenvalues between 0 and 2,
# I - L has eigenvalues between -1 and 1. ARPACK is most efficient
# when finding eigenvalues of largest magnitude (keyword which='LM')
# and when these eigenvalues are very large compared to the rest.
# For very large, very sparse graphs, I - L can have many, many
# eigenvalues very near 1.0. This leads to slow convergence. So
# instead, we'll use ARPACK's shift-invert mode, asking for the
# eigenvalues near 1.0. This effectively spreads-out the spectrum
# near 1.0 and leads to much faster convergence: potentially an
# orders-of-magnitude speedup over simply using keyword which='LA'
# in standard mode.
try:
# We are computing the opposite of the laplacian inplace so as
# to spare a memory allocation of a possibly very large array
laplacian *= -1
v0 = random_state.uniform(-1, 1, laplacian.shape[0])
lambdas, diffusion_map = eigsh(laplacian, k=n_components,
sigma=1.0, which='LM',
tol=eigen_tol, v0=v0)
embedding = diffusion_map.T[n_components::-1] * dd
except RuntimeError:
# When submatrices are exactly singular, an LU decomposition
# in arpack fails. We fallback to lobpcg
eigen_solver = "lobpcg"
# Revert the laplacian to its opposite to have lobpcg work
laplacian *= -1
if eigen_solver == 'amg':
# Use AMG to get a preconditioner and speed up the eigenvalue
# problem.
if not sparse.issparse(laplacian):
warnings.warn("AMG works better for sparse matrices")
# lobpcg needs double precision floats
laplacian = check_array(laplacian, dtype=np.float64,
accept_sparse=True)
laplacian = _set_diag(laplacian, 1, norm_laplacian)
ml = smoothed_aggregation_solver(check_array(laplacian, 'csr'))
M = ml.aspreconditioner()
X = random_state.rand(laplacian.shape[0], n_components + 1)
X[:, 0] = dd.ravel()
lambdas, diffusion_map = lobpcg(laplacian, X, M=M, tol=1.e-12,
largest=False)
embedding = diffusion_map.T * dd
if embedding.shape[0] == 1:
raise ValueError
elif eigen_solver == "lobpcg":
# lobpcg needs double precision floats
laplacian = check_array(laplacian, dtype=np.float64,
accept_sparse=True)
if n_nodes < 5 * n_components + 1:
# see note above under arpack why lobpcg has problems with small
# number of nodes
# lobpcg will fallback to eigh, so we short circuit it
if sparse.isspmatrix(laplacian):
laplacian = laplacian.toarray()
lambdas, diffusion_map = eigh(laplacian)
embedding = diffusion_map.T[:n_components] * dd
else:
laplacian = _set_diag(laplacian, 1, norm_laplacian)
# We increase the number of eigenvectors requested, as lobpcg
# doesn't behave well in low dimension
X = random_state.rand(laplacian.shape[0], n_components + 1)
X[:, 0] = dd.ravel()
lambdas, diffusion_map = lobpcg(laplacian, X, tol=1e-15,
largest=False, maxiter=2000)
embedding = diffusion_map.T[:n_components] * dd
if embedding.shape[0] == 1:
raise ValueError
embedding = _deterministic_vector_sign_flip(embedding)
if drop_first:
return embedding[1:n_components].T
else:
return embedding[:n_components].T
def null_space(M,
k,
k_skip=1,
eigen_solver='arpack',
tol=1E-6,
max_iter=100,
random_state=None):
"""
Find the null space of a matrix M.
Parameters
----------
M : array, matrix, sparse matrix, or LinearOperator
Input covariance matrix: should be symmetric positive semi-definite
k : number of eigenvalues/vectors to return
k_skip : number of low eigenvalues to skip.
eigen_solver : string ['arpack' | 'lobpcg' | 'dense']
arpack : use arnoldi iteration in shift-invert mode.
For this method, M may be a dense matrix, sparse matrix,
or general linear operator.
lobpcg : use locally optimized block-preconditioned conjugate gradient.
For this method, M may be a dense or sparse matrix.
A dense matrix M will be converted internally to a
csr sparse format.
dense : use standard dense matrix operations for the eigenvalue
decomposition. For this method, M must be an array
or matrix type. This method should be avoided for
large problems.
tol : tolerance for 'arpack' or 'lobpcg' methods.
not used if eigen_solver=='dense'
max_iter : maximum number of iterations for 'arpack' or 'lobpcg' methods
not used if eigen_solver=='dense'
"""
random_state = check_random_state(random_state)
if eigen_solver == 'arpack':
eigen_values, eigen_vectors = eigsh(M,
k + k_skip,
sigma=0.0,
tol=tol,
maxiter=max_iter)
return eigen_vectors[:, k_skip:], np.sum(eigen_values[k_skip:])
elif eigen_solver == 'lobpcg':
# initial vectors for iteration
X = np.random.rand(M.shape[0], k + k_skip)
try:
ml = pyamg.smoothed_aggregation_solver(M, symmetry='symmetric')
except TypeError:
ml = pyamg.smoothed_aggregation_solver(M, mat_flag='symmetric')
prec = ml.aspreconditioner()
# compute eigenvalues and eigenvectors with LOBPCG
eigen_values, eigen_vectors = linalg.lobpcg(M,
X,
M=prec,
largest=False,
tol=tol,
maxiter=max_iter)
index = np.argsort(eigen_values)
return (eigen_vectors[:, index[k_skip:]],
np.sum(eigen_values[index[k_skip:]]))
elif eigen_solver == 'dense':
M = np.asarray(M)
eigen_values, eigen_vectors = eigh(M,
eigvals=(k_skip, k + k_skip),
overwrite_a=True)
index = np.argsort(np.abs(eigen_values))
return eigen_vectors[:, index], np.sum(eigen_values)
else:
raise ValueError("Unrecognized eigen_solver '%s'" % eigen_solver)
k = arange(1,n+1)
w_ex = sort(1./(16.*pow(cos(0.5*k*pi/(n+1)),4))) # exact eigenvalues
return A,B, w_ex
m = 3 # Blocksize
#
# Large scale
#
n = 2500
A,B, w_ex = sakurai(n) # Mikota pair
X = rand(n,m)
data = []
tt = time.clock()
eigs,vecs, resnh = lobpcg(X,A,B, residualTolerance=1e-6, maxIterations=500, retResidualNormsHistory=1)
data.append(time.clock()-tt)
print('Results by LOBPCG for n='+str(n))
print()
print(eigs)
print()
print('Exact eigenvalues')
print()
print(w_ex[:m])
print()
print('Elapsed time',data[0])
loglog(arange(1,n+1),w_ex,'b.')
xlabel(r'Number $i$')
ylabel(r'$\lambda_i$')
title('Eigenvalue distribution')
show()
def fem_laplacian(points, faces, spectrum_size=10, normalization=None,
verbose=False):
"""
Compute linear finite-element method Laplace-Beltrami spectrum
after Martin Reuter's MATLAB code.
Comparison of fem_laplacian() with Martin Reuter's Matlab eigenvalues:
fem_laplacian() results for Twins-2-1 left hemisphere (6 values):
[4.829758648026221e-18,
0.0001284173002467199,
0.0002715181572272745,
0.0003205150847159417,
0.0004701628070486448,
0.0005768904023010318]
Martin Reuter's shapeDNA-tria Matlab code:
{-4.7207711983791511358e-18 ;
0.00012841730024672144738 ;
0.00027151815722727096853 ;
0.00032051508471592313632 ;
0.0004701628070486902353 ;
0.00057689040230097490998 }
fem_laplacian() results for Twins-2-1 left postcentral (1022):
[6.3469513010430304e-18,
0.0005178862383467463,
0.0017434911095630772,
0.003667561767487686,
0.005429017880363784,
0.006309346984678924]
Martin Reuter's Matlab code:
{-2.1954862991027e-18 ;
0.0005178862383468 ;
0.0017434911095628 ;
0.0036675617674875 ;
0.0054290178803611 ;
0.006309346984678 }
Julien Lefevre, regarding comparison with Spongy results:
"I have done some comparisons between my Matlab codes and yours
on python and everything sounds perfect:
The evaluation has been done only for one mesh (about 10000 vertices).
- L2 error between your A and B matrices and mine are about 1e-16.
- I have also compared eigenvalues of the generalized problem;
even if the error is slightly increasing, it remains on the order
of machine precision.
- computation time for 1000 eigenvalues was 67s with python
versus 63s in matlab. And it is quite the same behavior for lower orders.
- Since the eigenvalues are increasing with order,
it is also interesting to look at the relative error...
high frequencies are not so much perturbed."
Parameters
----------
points : list of lists of 3 floats
x,y,z coordinates for each vertex of the structure
faces : list of lists of 3 integers
3 indices to vertices that form a triangle on the mesh
spectrum_size : integer
number of eigenvalues to be computed (the length of the spectrum)
normalization : string
the method used to normalize eigenvalues ('area' or None)
if "area", use area of the 2D structure as in Reuter et al. 2006
verbose : bool
print statements?
Returns
-------
spectrum : list
first spectrum_size eigenvalues for Laplace-Beltrami spectrum
Examples
--------
>>> import numpy as np
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> # Define a cube:
>>> points = [[0,0,0], [0,1,0], [1,1,0], [1,0,0],
... [0,0,1], [0,1,1], [1,1,1], [1,0,1]]
>>> faces = [[0,1,2], [2,3,0], [4,5,6], [6,7,4], [0,4,7], [7,3,0],
... [0,4,5], [5,1,0], [1,5,6], [6,2,1], [3,7,6], [6,2,3]]
>>> spectrum = fem_laplacian(points, faces, spectrum_size=3,
... normalization=None, verbose=False)
>>> print(np.array_str(np.array(spectrum[1::]),
... precision=5, suppress_small=True))
[ 4.58359 4.8 ]
>>> spectrum = fem_laplacian(points, faces, spectrum_size=3,
... normalization="area", verbose=False)
>>> print(np.array_str(np.array(spectrum[1::]),
... precision=5, suppress_small=True))
[ 27.50155 28.8 ]
>>> # Spectrum for entire left hemisphere of Twins-2-1:
>>> from mindboggle.mio.vtks import read_vtk
>>> from mindboggle.mio.fetch_data import prep_tests
>>> urls, fetch_data = prep_tests()
>>> label_file = fetch_data(urls['left_freesurfer_labels'], '', '.vtk')
>>> points, f1,f2, faces, labels, f3,f4,f5 = read_vtk(label_file)
>>> spectrum = fem_laplacian(points, faces, spectrum_size=6,
... normalization=None, verbose=False)
>>> print(np.array_str(np.array(spectrum[1::]),
... precision=5, suppress_small=True))
[ 0.00013 0.00027 0.00032 0.00047 0.00058]
>>> # Spectrum for Twins-2-1 left postcentral pial surface (22):
>>> from mindboggle.guts.mesh import keep_faces, reindex_faces_points
>>> I22 = [i for i,x in enumerate(labels) if x==1022] # postcentral
>>> faces = keep_faces(faces, I22)
>>> faces, points, o1 = reindex_faces_points(faces, points)
>>> spectrum = fem_laplacian(points, faces, spectrum_size=6,
... normalization=None, verbose=False)
>>> print(np.array_str(np.array(spectrum[1::]),
... precision=5, suppress_small=True))
[ 0.00057 0.00189 0.00432 0.00691 0.00775]
>>> # Area-normalized spectrum for a single label (postcentral):
>>> spectrum = fem_laplacian(points, faces, spectrum_size=6,
... normalization="area", verbose=False)
>>> print(np.array_str(np.array(spectrum[1::]),
... precision=5, suppress_small=True))
[ 2.69259 8.97865 20.44857 32.74477 36.739 ]
"""
from scipy.sparse.linalg import eigsh, lobpcg
import numpy as np
from mindboggle.shapes.laplace_beltrami import computeAB
# ----------------------------------------------------------------
# Compute A and B matrices (from Reuter et al., 2009):
# ----------------------------------------------------------------
A, B = computeAB(points, faces)
if A.shape[0] <= spectrum_size:
if verbose:
print("The 3D shape has too few vertices ({0} <= {1}). Skip.".
format(A.shape[0], spectrum_size))
return None
# ----------------------------------------------------------------
# Use the eigsh eigensolver:
# ----------------------------------------------------------------
try :
# eigs is for nonsymmetric matrices while
# eigsh is for real-symmetric or complex-Hermitian matrices:
eigenvalues, eigenvectors = eigsh(A, k=spectrum_size, M=B,
sigma=-0.01)
spectrum = eigenvalues.tolist()
# ----------------------------------------------------------------
# Use the lobpcg eigensolver:
# ----------------------------------------------------------------
except RuntimeError:
if verbose:
print("eigsh() failed. Now try lobpcg.")
print("Warning: lobpcg can produce different results from "
"Reuter (2006) shapeDNA-tria software.")
# Initial eigenvector values:
init_eigenvecs = np.random.random((A.shape[0], spectrum_size))
# maxiter = 40 forces lobpcg to use 20 iterations.
# Strangely, largest=false finds largest eigenvalues
# and largest=True gives the smallest eigenvalues:
eigenvalues, eigenvectors = lobpcg(A, init_eigenvecs, B=B,
largest=True, maxiter=40)
# Extract the real parts:
spectrum = [value.real for value in eigenvalues]
# For some reason, the eigenvalues from lobpcg are not sorted:
spectrum.sort()
# ----------------------------------------------------------------
# Normalize by area:
# ----------------------------------------------------------------
if normalization == "area":
spectrum = area_normalize(points, faces, spectrum)
if verbose:
print("Compute area-normalized linear FEM Laplace-Beltrami "
"spectrum")
else:
if verbose:
print("Compute linear FEM Laplace-Beltrami spectrum")
return spectrum
def fem_laplacian(points, faces, n_eigenvalues=6, normalization=None):
"""
Compute linear finite-element method Laplace-Beltrami spectrum
after Martin Reuter's MATLAB code.
Note ::
Compare fem_laplacian() with Martin Reuter's Matlab code output:
fem_laplacian() results for Twins-2-1 left hemisphere:
[4.829758648026223e-18,
0.00012841730024671977,
0.0002715181572272744,
0.00032051508471594173,
0.000470162807048644,
0.0005768904023010327]
Martin Reuter's Matlab code:
Creator: ./shapeDNA-tria
Refine: 0
Degree: 1
Dimension: 2
Elements: 290134
DoF: 145069
NumEW: 6
Area: 110016
Volume: 534346
BLength: 0
EulerChar: 2
Time(pre) : 2
Time(calcAB) : 0
Time(calcEW) : 7
Time(total ) : 9
Eigenvalues:
{-4.7207711983791511358e-18 ;
0.00012841730024672144738 ;
0.00027151815722727096853 ;
0.00032051508471592313632 ;
0.0004701628070486902353 ;
0.00057689040230097490998 }
fem_laplacian() results for Twins-2-1 left hemisphere postcentral:
[6.346951301043029e-18,
0.0005178862383467465,
0.0017434911095630787,
0.0036675617674876916,
0.005429017880363785,
0.006309346984678927]
Martin Reuter's Matlab code:
-2.1954862991027e-18
0.0005178862383468
0.0017434911095628
0.0036675617674875
0.0054290178803611
0.006309346984678
Parameters
----------
points : list of lists of 3 floats
x,y,z coordinates for each vertex of the structure
faces : list of lists of 3 integers
3 indices to vertices that form a triangle on the mesh
n_eigenvalues : integer
number of eigenvalues to be computed (the length of the spectrum)
normalization : string
the method used to normalize eigenvalues ('area' or None)
if "area", use area of the 2D structure as in Reuter et al. 2006
Returns
-------
spectrum : list
first n_eigenvalues eigenvalues for Laplace-Beltrami spectrum
Examples
--------
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> # Define a cube:
>>> points = [[0,0,0], [0,1,0], [1,1,0], [1,0,0],
>>> [0,0,1], [0,1,1], [1,1,1], [1,0,1]]
>>> faces = [[0,1,2], [2,3,0], [4,5,6], [6,7,4], [0,4,7], [7,3,0],
>>> [0,4,5], [5,1,0], [1,5,6], [6,2,1], [3,7,6], [6,2,3]]
>>> fem_laplacian(points, faces, n_eigenvalues=3, normalization=None)
[7.401486830834377e-17, 4.58359213500127, 4.799999999999998]
>>> fem_laplacian(points, faces, n_eigenvalues=3, normalization="area")
[1.2335811384723967e-17, 0.76393202250021175, 0.79999999999999949]
>>> # Spectrum for entire left hemisphere of Twins-2-1:
>>> import os
>>> from mindboggle.utils.io_vtk import read_faces_points
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> path = os.environ['MINDBOGGLE_DATA']
>>> vtk_file = os.path.join(path, 'arno', 'labels',
>>> 'lh.labels.DKT25.manual.vtk')
>>> faces, points, npoints = read_faces_points(vtk_file)
>>> fem_laplacian(points, faces, n_eigenvalues=6, normalization=None)
[4.829758648026223e-18,
0.00012841730024671904,
0.00027151815722727406,
0.00032051508471594146,
0.0004701628070486449,
0.0005768904023010303]
>>> # Spectrum for Twins-2-1 left hemisphere postcentral (label 22):
>>> import os
>>> from mindboggle.utils.io_vtk import read_faces_points
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> path = os.environ['MINDBOGGLE_DATA']
>>> label_file = os.path.join(path, 'arno', 'labels', 'label22.vtk')
>>> faces, points, npoints = read_faces_points(label_file)
>>> print("{0}".format(fem_laplacian(points, faces, n_eigenvalues=6,
>>> normalization=None)))
[6.346951301043029e-18,
0.0005178862383467465,
0.0017434911095630787,
0.0036675617674876916,
0.005429017880363785,
0.006309346984678927]
>>> # Area-normalized spectrum for a single label (postcentral):
>>> print("{0}".format(fem_laplacian(points, faces, n_eigenvalues=6,
>>> normalization="area")))
[1.1410192787181146e-21,
9.310268097367214e-08,
3.1343504525679715e-07,
6.593336681038091e-07,
9.759983608165455e-07,
1.1342589857996225e-06]
>>> # testing LBO on previously failed folds
>>> import subprocess
>>> cmd = ["find", "/media/USBDATA/data/Mindboggle_MRI/MB101/results/features/", "-name", "fold_*.vtk"]
>>> process = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
>>> out, err = process.communicate()
>>> pblm_vtks = out.split()
>>> import mindboggle.shapes.laplace_beltrami
>>> for vtk_file in pblm_vtks:
mindboggle.shapes.laplace_beltrami.spectrum_from_file(vtk_file)
"""
from scipy.sparse.linalg import eigsh, lobpcg
import numpy as np
from mindboggle.shapes.laplace_beltrami import computeAB
#-----------------------------------------------------------------
# Compute A and B matrices (from Reuter et al., 2009):
#-----------------------------------------------------------------
A, B = computeAB(points, faces)
if A.shape[0] <= n_eigenvalues:
print("The 3D shape has too few vertices ({0} <= {1}). Skip.".
format(A.shape[0], n_eigenvalues))
return None
#-----------------------------------------------------------------
# Use the eigsh eigensolver:
#-----------------------------------------------------------------
try :
# eigs is for nonsymmetric matrices while
# eigsh is for real-symmetric or complex-Hermitian matrices:
eigenvalues, eigenvectors = eigsh(A, k=n_eigenvalues, M=B,
sigma=0)
spectrum = eigenvalues.tolist()
#-----------------------------------------------------------------
# Use the lobpcg eigensolver:
#-----------------------------------------------------------------
except RuntimeError:
print("eigsh() failed. Now try lobpcg.")
print("Warning: lobpcg can produce different results from Reuter"
"et al.'s (2006) shapeDNA-tria software.")
# Initial eigenvector values:
init_eigenvecs = np.random.random((A.shape[0], n_eigenvalues))
# maxiter = 40 forces lobpcg to use 20 iterations.
# Strangely, largest=false finds largest eigenvalues
# and largest=True gives the smallest eigenvalues:
eigenvalues, eigenvectors = lobpcg(A, init_eigenvecs, B=B,
largest=True, maxiter=40)
# Extract the real parts:
spectrum = [value.real for value in eigenvalues]
# For some reason, the eigenvalues from lobpcg are not sorted:
spectrum.sort()
#-----------------------------------------------------------------
# Normalize by area:
#-----------------------------------------------------------------
if normalization == "area":
spectrum = area_normalize(points, faces, spectrum)
print("Compute area-normalized linear FEM Laplace-Beltrami spectrum")
else:
print("Compute linear FEM Laplace-Beltrami spectrum")
return spectrum
def solveSparse(Hs, run_lobpcg=False, minimal=False, verbose=False,
more=False, exact=False):
'''Finds a subset of the eigenstates/eigenvalues for a sparse
formatted Hamiltonian'''
sols = {}
N = int(round(np.log2(Hs.shape[0]))) # number of cells
## EIGSH
if verbose:
print '-'*40
print 'EIGSH...\n'
if minimal: # only the lowest two states
K_EIGSH = 2
elif more: # can only find ground state for 2x2 system using eigsh
K_EIGSH = 1 if N == 1 else min(pow(2, N)-1, 11*N)
else:
K_EIGSH = 1 if N == 1 else 3*N
K_EIGSH = min(K_EIGSH, Hs.shape[0]-1)
t1 = clock()
# run eigsh
try:
if exact:
e_vals, e_vecs = eigh(Hs.todense())
else:
e_vals, e_vecs = eigsh(Hs, k=K_EIGSH, tol=TOL_EIGSH, which='SA')
except: # should not happen unless K_EIGSH assignment rewritten
try:
e_vals, e_vecs = eigsh(Hs, k=2, tol=TOL_EIGSH, which='SA')
except:
if verbose:
print 'Insufficient dim for sparse methods. Running eigh'
e_vals, e_vecs = eigh(Hs.todense())
if verbose:
print 'Time elapsed (seconds): %f\n' % (clock()-t1)
sols['eigsh'] = {}
sols['eigsh']['vals'] = e_vals
sols['eigsh']['vecs'] = e_vecs
###################################################################
## RUN LOBPCG
### LOBPCG only works for positive definite matrices and hence is only
### reliable for the ground state (for which the n-th leading minor
### remains positive definite in the cholesky decomposition)
if run_lobpcg:
if verbose:
print '-'*40
print 'LOBPCG...\n'
t2 = clock()
# guess solution
approx = np.ones([N, 1], dtype=float)
# offset Hamiltonian to assert positive definite (for ground state)
Hs = Hs+sp.diags(np.ones([1, N], dtype=float)*H_OFFSET, [0])
# run lobpcg, remove offset
e_vals, e_vecs = lobpcg(Hs, approx, tol=TOL_LOBPCG)
e_vals -= H_OFFSET
if verbose:
print 'Time elapsed (seconds): %f\n' % (clock()-t2)
sols['lobpcg'] = {}
sols['lobpcg']['vals'] = e_vals
sols['lobpcg']['vecs'] = e_vecs
return sols
V,E = mesh.regular_triangle_mesh(20,6)
if meshnum==2:
from scipy.io import loadmat
mesh = loadmat('crack_mesh.mat')
V=mesh['V']
E=mesh['E']
A = graph_laplacian(V,E)
# construct preconditioner
ml = smoothed_aggregation_solver(A, coarse_solver='pinv2',max_coarse=10)
M = ml.aspreconditioner()
# solve for lowest two modes: constant vector and Fiedler vector
X = scipy.rand(A.shape[0], 2)
(eval,evec,res) = lobpcg(A, X, M=None, tol=1e-12, largest=False, \
verbosityLevel=0, retResidualNormsHistory=True)
fiedler = evec[:,1]
# use the median of the Fiedler vector as the separator
vmed = numpy.median(fiedler)
v = numpy.zeros((A.shape[0],))
K = numpy.where(fiedler<=vmed)[0]
v[K]=-1
K = numpy.where(fiedler>vmed)[0]
v[K]=1
# plot the mesh and partition
trimesh(V,E)
sub = pylab.gca()
sub.hold(True)
def eigen_decomposition(G, n_components=8, eigen_solver='auto',
random_state=None,
drop_first=True, largest=True, solver_kwds=None):
"""
Function to compute the eigendecomposition of a square matrix.
Parameters
----------
G : array_like or sparse matrix
The square matrix for which to compute the eigen-decomposition.
n_components : integer, optional
The number of eigenvectors to return
eigen_solver : {'auto', 'dense', 'arpack', 'lobpcg', or 'amg'}
'auto' :
attempt to choose the best method for input data (default)
'dense' :
use standard dense matrix operations for the eigenvalue decomposition.
For this method, M must be an array or matrix type.
This method should be avoided for large problems.
'arpack' :
use arnoldi iteration in shift-invert mode. For this method,
M may be a dense matrix, sparse matrix, or general linear operator.
Warning: ARPACK can be unstable for some problems. It is best to
try several random seeds in order to check results.
'lobpcg' :
Locally Optimal Block Preconditioned Conjugate Gradient Method.
A preconditioned eigensolver for large symmetric positive definite
(SPD) generalized eigenproblems.
'amg' :
Algebraic Multigrid solver (requires ``pyamg`` to be installed)
It can be faster on very large, sparse problems, but may also lead
to instabilities.
random_state : int seed, RandomState instance, or None (default)
A pseudo random number generator used for the initialization of the
lobpcg eigen vectors decomposition when eigen_solver == 'amg'.
By default, arpack is used.
solver_kwds : any additional keyword arguments to pass to the selected eigen_solver
Returns
-------
lambdas, diffusion_map : eigenvalues, eigenvectors
"""
n_nodes = G.shape[0]
if drop_first:
n_components = n_components + 1
eigen_solver, solver_kwds = check_eigen_solver(eigen_solver, solver_kwds,
size=n_nodes,
nvec=n_components)
random_state = check_random_state(random_state)
# Convert G to best type for eigendecomposition
if sparse.issparse(G):
if G.getformat() is not 'csr':
G.tocsr()
G = G.astype(np.float)
# Check for symmetry
is_symmetric = _is_symmetric(G)
# Try Eigen Methods:
if eigen_solver == 'arpack':
# This matches the internal initial state used by ARPACK
v0 = random_state.uniform(-1, 1, G.shape[0])
if is_symmetric:
if largest:
which = 'LM'
else:
which = 'SM'
lambdas, diffusion_map = eigsh(G, k=n_components, which=which,
v0=v0,**(solver_kwds or {}))
else:
if largest:
which = 'LR'
else:
which = 'SR'
lambdas, diffusion_map = eigs(G, k=n_components, which=which,
**(solver_kwds or {}))
lambdas = np.real(lambdas)
diffusion_map = np.real(diffusion_map)
elif eigen_solver == 'amg':
# separate amg & lobpcg keywords:
if solver_kwds is not None:
amg_kwds = {}
lobpcg_kwds = solver_kwds.copy()
for kwd in AMG_KWDS:
if kwd in solver_kwds.keys():
amg_kwds[kwd] = solver_kwds[kwd]
del lobpcg_kwds[kwd]
else:
amg_kwds = None
lobpcg_kwds = None
if not is_symmetric:
raise ValueError("lobpcg requires symmetric matrices.")
if not sparse.issparse(G):
warnings.warn("AMG works better for sparse matrices")
# Use AMG to get a preconditioner and speed up the eigenvalue problem.
ml = smoothed_aggregation_solver(check_array(G, accept_sparse = ['csr']),**(amg_kwds or {}))
M = ml.aspreconditioner()
n_find = min(n_nodes, 5 + 2*n_components)
X = random_state.rand(n_nodes, n_find)
X[:, 0] = (G.diagonal()).ravel()
lambdas, diffusion_map = lobpcg(G, X, M=M, largest=largest,**(lobpcg_kwds or {}))
sort_order = np.argsort(lambdas)
if largest:
lambdas = lambdas[sort_order[::-1]]
diffusion_map = diffusion_map[:, sort_order[::-1]]
else:
lambdas = lambdas[sort_order]
diffusion_map = diffusion_map[:, sort_order]
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == "lobpcg":
if not is_symmetric:
raise ValueError("lobpcg requires symmetric matrices.")
n_find = min(n_nodes, 5 + 2*n_components)
X = random_state.rand(n_nodes, n_find)
lambdas, diffusion_map = lobpcg(G, X, largest=largest,**(solver_kwds or {}))
sort_order = np.argsort(lambdas)
if largest:
lambdas = lambdas[sort_order[::-1]]
diffusion_map = diffusion_map[:, sort_order[::-1]]
else:
lambdas = lambdas[sort_order]
diffusion_map = diffusion_map[:, sort_order]
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == 'dense':
if sparse.isspmatrix(G):
G = G.todense()
if is_symmetric:
lambdas, diffusion_map = eigh(G,**(solver_kwds or {}))
else:
lambdas, diffusion_map = eig(G,**(solver_kwds or {}))
if largest:# eigh always returns eigenvalues in ascending order
lambdas = lambdas[::-1] # reverse order the e-values
diffusion_map = diffusion_map[:, ::-1] # reverse order the vectors
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
return (lambdas, diffusion_map)
def spectral_embedding(adjacency, n_components=8, mode=None,
random_state=None):
"""Project the sample on the first eigen vectors of the graph Laplacian
The adjacency matrix is used to compute a normalized graph Laplacian
whose spectrum (especially the eigen vectors associated to the
smallest eigen values) has an interpretation in terms of minimal
number of cuts necessary to split the graph into comparably sized
components.
This embedding can also 'work' even if the ``adjacency`` variable is
not strictly the adjacency matrix of a graph but more generally
an affinity or similarity matrix between samples (for instance the
heat kernel of a euclidean distance matrix or a k-NN matrix).
However care must taken to always make the affinity matrix symmetric
so that the eigen vector decomposition works as expected.
Parameters
-----------
adjacency: array-like or sparse matrix, shape: (n_samples, n_samples)
The adjacency matrix of the graph to embed.
n_components: integer, optional
The dimension of the projection subspace.
mode: {None, 'arpack' or 'amg'}
The eigenvalue decomposition strategy to use. AMG requires pyamg
to be installed. It can be faster on very large, sparse problems,
but may also lead to instabilities
random_state: int seed, RandomState instance, or None (default)
A pseudo random number generator used for the initialization of the
lobpcg eigen vectors decomposition when mode == 'amg'. By default
arpack is used.
Returns
--------
embedding: array, shape: (n_samples, n_components)
The reduced samples
Notes
------
The graph should contain only one connected component, elsewhere the
results make little sense.
"""
from scipy import sparse
from ..utils.arpack import eigsh
from scipy.sparse.linalg import lobpcg
try:
from pyamg import smoothed_aggregation_solver
except ImportError:
if mode == "amg":
raise ValueError("The mode was set to 'amg', but pyamg is "
"not available.")
random_state = check_random_state(random_state)
n_nodes = adjacency.shape[0]
# XXX: Should we check that the matrices given is symmetric
if mode is None:
mode = 'arpack'
laplacian, dd = graph_laplacian(adjacency,
normed=True, return_diag=True)
if (mode == 'arpack'
or not sparse.isspmatrix(laplacian)
or n_nodes < 5 * n_components):
# lobpcg used with mode='amg' has bugs for low number of nodes
# We need to put the diagonal at zero
if not sparse.isspmatrix(laplacian):
laplacian.flat[::n_nodes + 1] = 0
else:
laplacian = laplacian.tocoo()
diag_idx = (laplacian.row == laplacian.col)
laplacian.data[diag_idx] = 0
# If the matrix has a small number of diagonals (as in the
# case of structured matrices comming from images), the
# dia format might be best suited for matvec products:
n_diags = np.unique(laplacian.row - laplacian.col).size
if n_diags <= 7:
# 3 or less outer diagonals on each side
laplacian = laplacian.todia()
else:
# csr has the fastest matvec and is thus best suited to
# arpack
laplacian = laplacian.tocsr()
# Here we'll use shift-invert mode for fast eigenvalues
# (see http://docs.scipy.org/doc/scipy/reference/tutorial/arpack.html
# for a short explanation of what this means)
# Because the normalized Laplacian has eigenvalues between 0 and 2,
# I - L has eigenvalues between -1 and 1. ARPACK is most efficient
# when finding eigenvalues of largest magnitude (keyword which='LM')
# and when these eigenvalues are very large compared to the rest.
# For very large, very sparse graphs, I - L can have many, many
# eigenvalues very near 1.0. This leads to slow convergence. So
# instead, we'll use ARPACK's shift-invert mode, asking for the
# eigenvalues near 1.0. This effectively spreads-out the spectrum
# near 1.0 and leads to much faster convergence: potentially an
# orders-of-magnitude speedup over simply using keyword which='LA'
# in standard mode.
lambdas, diffusion_map = eigsh(-laplacian, k=n_components,
sigma=1.0, which='LM')
embedding = diffusion_map.T[::-1] * dd
elif mode == 'amg':
# Use AMG to get a preconditioner and speed up the eigenvalue
# problem.
laplacian = laplacian.astype(np.float) # lobpcg needs native floats
ml = smoothed_aggregation_solver(laplacian.tocsr())
X = random_state.rand(laplacian.shape[0], n_components)
X[:, 0] = 1. / dd.ravel()
M = ml.aspreconditioner()
lambdas, diffusion_map = lobpcg(laplacian, X, M=M, tol=1.e-12,
largest=False)
embedding = diffusion_map.T * dd
if embedding.shape[0] == 1:
raise ValueError
else:
raise ValueError("Unknown value for mode: '%s'."
"Should be 'amg' or 'arpack'" % mode)
return embedding
k = arange(1,n+1)
w_ex = sort(1./(16.*pow(cos(0.5*k*pi/(n+1)),4))) # exact eigenvalues
return A,B, w_ex
m = 3 # Blocksize
#
# Large scale
#
n = 2500
A,B, w_ex = sakurai(n) # Mikota pair
X = rand(n,m)
data=[]
tt = time.clock()
eigs,vecs, resnh = lobpcg(A,X,B, tol=1e-6, maxiter=500, retResidualNormsHistory=1)
data.append(time.clock()-tt)
print 'Results by LOBPCG for n='+str(n)
print
print eigs
print
print 'Exact eigenvalues'
print
print w_ex[:m]
print
print 'Elapsed time',data[0]
loglog(arange(1,n+1),w_ex,'b.')
xlabel(r'Number $i$')
ylabel(r'$\lambda_i$')
title('Eigenvalue distribution')
show()
def spectral_embedding(adjacency, n_components=8, mode=None,
random_state=None):
"""Project the sample on the first eigen vectors of the graph Laplacian
The adjacency matrix is used to compute a normalized graph Laplacian
whose spectrum (especially the eigen vectors associated to the
smallest eigen values) has an interpretation in terms of minimal
number of cuts necessary to split the graph into comparably sized
components.
This embedding can also 'work' even if the ``adjacency`` variable is
not strictly the adjacency matrix of a graph but more generally
an affinity or similarity matrix between samples (for instance the
heat kernel of a euclidean distance matrix or a k-NN matrix).
However care must taken to always make the affinity matrix symmetric
so that the eigen vector decomposition works as expected.
Parameters
-----------
adjacency: array-like or sparse matrix, shape: (n_samples, n_samples)
The adjacency matrix of the graph to embed.
n_components: integer, optional
The dimension of the projection subspace.
mode: {None, 'arpack' or 'amg'}
The eigenvalue decomposition strategy to use. AMG (Algebraic
MultiGrid) is much faster, but requires pyamg to be
installed.
random_state: int seed, RandomState instance, or None (default)
A pseudo random number generator used for the initialization of the
lobpcg eigen vectors decomposition when mode == 'amg'.
Returns
--------
embedding: array, shape: (n_samples, n_components)
The reduced samples
Notes
------
The graph should contain only one connected component, elsewhere the
results make little sense.
"""
from scipy import sparse
from ..utils.fixes import arpack_eigsh
from scipy.sparse.linalg import lobpcg
try:
from pyamg import smoothed_aggregation_solver
amg_loaded = True
except ImportError:
amg_loaded = False
random_state = check_random_state(random_state)
n_nodes = adjacency.shape[0]
# XXX: Should we check that the matrices given is symmetric
if not amg_loaded:
warnings.warn('pyamg not available, using scipy.sparse')
if mode is None:
mode = ('amg' if amg_loaded else 'arpack')
laplacian, dd = graph_laplacian(adjacency,
normed=True, return_diag=True)
if (mode == 'arpack'
or not sparse.isspmatrix(laplacian)
or n_nodes < 5 * n_components):
# lobpcg used with mode='amg' has bugs for low number of nodes
# We need to put the diagonal at zero
if not sparse.isspmatrix(laplacian):
laplacian[::n_nodes + 1] = 0
else:
laplacian = laplacian.tocoo()
diag_idx = (laplacian.row == laplacian.col)
laplacian.data[diag_idx] = 0
# If the matrix has a small number of diagonals (as in the
# case of structured matrices comming from images), the
# dia format might be best suited for matvec products:
n_diags = np.unique(laplacian.row - laplacian.col).size
if n_diags <= 7:
# 3 or less outer diagonals on each side
laplacian = laplacian.todia()
else:
# csr has the fastest matvec and is thus best suited to
# arpack
laplacian = laplacian.tocsr()
lambdas, diffusion_map = arpack_eigsh(-laplacian, k=n_components,
which='LA')
embedding = diffusion_map.T[::-1] * dd
elif mode == 'amg':
# Use AMG to get a preconditionner and speed up the eigenvalue
# problem.
laplacian = laplacian.astype(np.float) # lobpcg needs native floats
ml = smoothed_aggregation_solver(laplacian.tocsr())
X = random_state.rand(laplacian.shape[0], n_components)
X[:, 0] = 1. / dd.ravel()
M = ml.aspreconditioner()
lambdas, diffusion_map = lobpcg(laplacian, X, M=M, tol=1.e-12,
largest=False)
embedding = diffusion_map.T * dd
if embedding.shape[0] == 1:
raise ValueError
else:
raise ValueError("Unknown value for mode: '%s'."
"Should be 'amg' or 'arpack'" % mode)
return embedding
def eigen_decomposition(G,
n_components=8,
eigen_solver='auto',
random_state=None,
drop_first=True,
largest=True,
solver_kwds=None):
"""
Function to compute the eigendecomposition of a square matrix.
Parameters
----------
G : array_like or sparse matrix
The square matrix for which to compute the eigen-decomposition.
n_components : integer, optional
The number of eigenvectors to return
eigen_solver : {'auto', 'dense', 'arpack', 'lobpcg', or 'amg'}
'auto' :
attempt to choose the best method for input data (default)
'dense' :
use standard dense matrix operations for the eigenvalue decomposition.
For this method, M must be an array or matrix type.
This method should be avoided for large problems.
'arpack' :
use arnoldi iteration in shift-invert mode. For this method,
M may be a dense matrix, sparse matrix, or general linear operator.
Warning: ARPACK can be unstable for some problems. It is best to
try several random seeds in order to check results.
'lobpcg' :
Locally Optimal Block Preconditioned Conjugate Gradient Method.
A preconditioned eigensolver for large symmetric positive definite
(SPD) generalized eigenproblems.
'amg' :
Algebraic Multigrid solver (requires ``pyamg`` to be installed)
It can be faster on very large, sparse problems, but may also lead
to instabilities.
random_state : int seed, RandomState instance, or None (default)
A pseudo random number generator used for the initialization of the
lobpcg eigen vectors decomposition when eigen_solver == 'amg'.
By default, arpack is used.
solver_kwds : any additional keyword arguments to pass to the selected eigen_solver
Returns
-------
lambdas, diffusion_map : eigenvalues, eigenvectors
"""
n_nodes = G.shape[0]
if drop_first:
n_components = n_components + 1
eigen_solver, solver_kwds = check_eigen_solver(eigen_solver,
solver_kwds,
size=n_nodes,
nvec=n_components)
random_state = check_random_state(random_state)
# Convert G to best type for eigendecomposition
if sparse.issparse(G):
if G.getformat() is not 'csr':
G.tocsr()
G = G.astype(np.float)
# Check for symmetry
is_symmetric = _is_symmetric(G)
# Try Eigen Methods:
if eigen_solver == 'arpack':
# This matches the internal initial state used by ARPACK
v0 = random_state.uniform(-1, 1, G.shape[0])
if is_symmetric:
if largest:
which = 'LM'
else:
which = 'SM'
lambdas, diffusion_map = eigsh(G,
k=n_components,
which=which,
v0=v0,
**(solver_kwds or {}))
else:
if largest:
which = 'LR'
else:
which = 'SR'
lambdas, diffusion_map = eigs(G,
k=n_components,
which=which,
**(solver_kwds or {}))
lambdas = np.real(lambdas)
diffusion_map = np.real(diffusion_map)
elif eigen_solver == 'amg':
# separate amg & lobpcg keywords:
if solver_kwds is not None:
amg_kwds = {}
lobpcg_kwds = solver_kwds.copy()
for kwd in AMG_KWDS:
if kwd in solver_kwds.keys():
amg_kwds[kwd] = solver_kwds[kwd]
del lobpcg_kwds[kwd]
else:
amg_kwds = None
lobpcg_kwds = None
if not is_symmetric:
raise ValueError("lobpcg requires symmetric matrices.")
if not sparse.issparse(G):
warnings.warn("AMG works better for sparse matrices")
# Use AMG to get a preconditioner and speed up the eigenvalue problem.
ml = smoothed_aggregation_solver(check_array(G, accept_sparse=['csr']),
**(amg_kwds or {}))
M = ml.aspreconditioner()
n_find = min(n_nodes, 5 + 2 * n_components)
X = random_state.rand(n_nodes, n_find)
X[:, 0] = (G.diagonal()).ravel()
lambdas, diffusion_map = lobpcg(G,
X,
M=M,
largest=largest,
**(lobpcg_kwds or {}))
sort_order = np.argsort(lambdas)
if largest:
lambdas = lambdas[sort_order[::-1]]
diffusion_map = diffusion_map[:, sort_order[::-1]]
else:
lambdas = lambdas[sort_order]
diffusion_map = diffusion_map[:, sort_order]
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == "lobpcg":
if not is_symmetric:
raise ValueError("lobpcg requires symmetric matrices.")
n_find = min(n_nodes, 5 + 2 * n_components)
X = random_state.rand(n_nodes, n_find)
lambdas, diffusion_map = lobpcg(G,
X,
largest=largest,
**(solver_kwds or {}))
sort_order = np.argsort(lambdas)
if largest:
lambdas = lambdas[sort_order[::-1]]
diffusion_map = diffusion_map[:, sort_order[::-1]]
else:
lambdas = lambdas[sort_order]
diffusion_map = diffusion_map[:, sort_order]
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == 'dense':
if sparse.isspmatrix(G):
G = G.todense()
if is_symmetric:
lambdas, diffusion_map = eigh(G, **(solver_kwds or {}))
else:
lambdas, diffusion_map = eig(G, **(solver_kwds or {}))
sort_index = np.argsort(lambdas)
lambdas = lambdas[sort_index]
diffusion_map[:, sort_index]
if largest: # eigh always returns eigenvalues in ascending order
lambdas = lambdas[::-1] # reverse order the e-values
diffusion_map = diffusion_map[:, ::-1] # reverse order the vectors
lambdas = lambdas[:n_components]
diffusion_map = diffusion_map[:, :n_components]
elif eigen_solver == 'slepc':
if is_symmetric:
lambdas, diffusion_map = slepc.get_eigenpairs(G,
npairs=n_components,
largest=largest)
return (lambdas, diffusion_map)
N = 100
K = 9
A = poisson((N,N), format='csr')
# create the AMG hierarchy
ml = smoothed_aggregation_solver(A)
# initial approximation to the K eigenvectors
X = scipy.rand(A.shape[0], K)
# preconditioner based on ml
M = ml.aspreconditioner()
# compute eigenvalues and eigenvectors with LOBPCG
W,V = lobpcg(A, X, M=M, tol=1e-8, largest=False)
#plot the eigenvectors
import pylab
pylab.figure(figsize=(9,9))
for i in range(K):
pylab.subplot(3, 3, i+1)
pylab.title('Eigenvector %d' % i)
pylab.pcolor(V[:,i].reshape(N,N))
pylab.axis('equal')
pylab.axis('off')
pylab.show()
def spectral_embedding(adjacency,
n_components=8,
eigen_solver=None,
random_state=None,
eigen_tol=0.0,
norm_laplacian=True,
drop_first=True):
"""Project the sample on the first eigenvectors of the graph Laplacian.
The adjacency matrix is used to compute a normalized graph Laplacian
whose spectrum (especially the eigenvectors associated to the
smallest eigenvalues) has an interpretation in terms of minimal
number of cuts necessary to split the graph into comparably sized
components.
This embedding can also 'work' even if the ``adjacency`` variable is
not strictly the adjacency matrix of a graph but more generally
an affinity or similarity matrix between samples (for instance the
heat kernel of a euclidean distance matrix or a k-NN matrix).
However care must taken to always make the affinity matrix symmetric
so that the eigenvector decomposition works as expected.
Note : Laplacian Eigenmaps is the actual algorithm implemented here.
Read more in the :ref:`User Guide <spectral_embedding>`.
Parameters
----------
adjacency : array-like or sparse matrix, shape: (n_samples, n_samples)
The adjacency matrix of the graph to embed.
n_components : integer, optional, default 8
The dimension of the projection subspace.
eigen_solver : {None, 'arpack', 'lobpcg', or 'amg'}, default None
The eigenvalue decomposition strategy to use. AMG requires pyamg
to be installed. It can be faster on very large, sparse problems,
but may also lead to instabilities.
random_state : int, RandomState instance or None, optional, default: None
A pseudo random number generator used for the initialization of the
lobpcg eigenvectors decomposition. If int, random_state is the seed
used by the random number generator; If RandomState instance,
random_state is the random number generator; If None, the random number
generator is the RandomState instance used by `np.random`. Used when
``solver`` == 'amg'.
eigen_tol : float, optional, default=0.0
Stopping criterion for eigendecomposition of the Laplacian matrix
when using arpack eigen_solver.
norm_laplacian : bool, optional, default=True
If True, then compute normalized Laplacian.
drop_first : bool, optional, default=True
Whether to drop the first eigenvector. For spectral embedding, this
should be True as the first eigenvector should be constant vector for
connected graph, but for spectral clustering, this should be kept as
False to retain the first eigenvector.
Returns
-------
embedding : array, shape=(n_samples, n_components)
The reduced samples.
Notes
-----
Spectral Embedding (Laplacian Eigenmaps) is most useful when the graph
has one connected component. If there graph has many components, the first
few eigenvectors will simply uncover the connected components of the graph.
References
----------
* https://en.wikipedia.org/wiki/LOBPCG
* Toward the Optimal Preconditioned Eigensolver: Locally Optimal
Block Preconditioned Conjugate Gradient Method
Andrew V. Knyazev
https://doi.org/10.1137%2FS1064827500366124
"""
adjacency = check_symmetric(adjacency)
try:
from pyamg import smoothed_aggregation_solver
except ImportError:
if eigen_solver == "amg":
raise ValueError("The eigen_solver was set to 'amg', but pyamg is "
"not available.")
if eigen_solver is None:
eigen_solver = 'arpack'
elif eigen_solver not in ('arpack', 'lobpcg', 'amg'):
raise ValueError("Unknown value for eigen_solver: '%s'."
"Should be 'amg', 'arpack', or 'lobpcg'" %
eigen_solver)
random_state = check_random_state(random_state)
n_nodes = adjacency.shape[0]
# Whether to drop the first eigenvector
if drop_first:
n_components = n_components + 1
if not _graph_is_connected(adjacency):
warnings.warn("Graph is not fully connected, spectral embedding"
" may not work as expected.")
laplacian, dd = csgraph_laplacian(adjacency,
normed=norm_laplacian,
return_diag=True)
if (eigen_solver == 'arpack' or eigen_solver != 'lobpcg' and
(not sparse.isspmatrix(laplacian) or n_nodes < 5 * n_components)):
# lobpcg used with eigen_solver='amg' has bugs for low number of nodes
# for details see the source code in scipy:
# https://github.com/scipy/scipy/blob/v0.11.0/scipy/sparse/linalg/eigen
# /lobpcg/lobpcg.py#L237
# or matlab:
# https://www.mathworks.com/matlabcentral/fileexchange/48-lobpcg-m
laplacian = _set_diag(laplacian, 1, norm_laplacian)
# Here we'll use shift-invert mode for fast eigenvalues
# (see https://docs.scipy.org/doc/scipy/reference/tutorial/arpack.html
# for a short explanation of what this means)
# Because the normalized Laplacian has eigenvalues between 0 and 2,
# I - L has eigenvalues between -1 and 1. ARPACK is most efficient
# when finding eigenvalues of largest magnitude (keyword which='LM')
# and when these eigenvalues are very large compared to the rest.
# For very large, very sparse graphs, I - L can have many, many
# eigenvalues very near 1.0. This leads to slow convergence. So
# instead, we'll use ARPACK's shift-invert mode, asking for the
# eigenvalues near 1.0. This effectively spreads-out the spectrum
# near 1.0 and leads to much faster convergence: potentially an
# orders-of-magnitude speedup over simply using keyword which='LA'
# in standard mode.
try:
# We are computing the opposite of the laplacian inplace so as
# to spare a memory allocation of a possibly very large array
laplacian *= -1
v0 = random_state.uniform(-1, 1, laplacian.shape[0])
lambdas, diffusion_map = eigsh(laplacian,
k=n_components,
sigma=1.0,
which='LM',
tol=eigen_tol,
v0=v0)
embedding = diffusion_map.T[n_components::-1]
if norm_laplacian:
embedding = embedding / dd
except RuntimeError:
# When submatrices are exactly singular, an LU decomposition
# in arpack fails. We fallback to lobpcg
eigen_solver = "lobpcg"
# Revert the laplacian to its opposite to have lobpcg work
laplacian *= -1
if eigen_solver == 'amg':
# Use AMG to get a preconditioner and speed up the eigenvalue
# problem.
if not sparse.issparse(laplacian):
warnings.warn("AMG works better for sparse matrices")
# lobpcg needs double precision floats
laplacian = check_array(laplacian,
dtype=np.float64,
accept_sparse=True)
laplacian = _set_diag(laplacian, 1, norm_laplacian)
ml = smoothed_aggregation_solver(check_array(laplacian, 'csr'))
M = ml.aspreconditioner()
X = random_state.rand(laplacian.shape[0], n_components + 1)
X[:, 0] = dd.ravel()
lambdas, diffusion_map = lobpcg(laplacian,
X,
M=M,
tol=1.e-12,
largest=False)
embedding = diffusion_map.T
if norm_laplacian:
embedding = embedding / dd
if embedding.shape[0] == 1:
raise ValueError
elif eigen_solver == "lobpcg":
# lobpcg needs double precision floats
laplacian = check_array(laplacian,
dtype=np.float64,
accept_sparse=True)
if n_nodes < 5 * n_components + 1:
# see note above under arpack why lobpcg has problems with small
# number of nodes
# lobpcg will fallback to eigh, so we short circuit it
if sparse.isspmatrix(laplacian):
laplacian = laplacian.toarray()
lambdas, diffusion_map = eigh(laplacian)
embedding = diffusion_map.T[:n_components]
if norm_laplacian:
embedding = embedding / dd
else:
laplacian = _set_diag(laplacian, 1, norm_laplacian)
# We increase the number of eigenvectors requested, as lobpcg
# doesn't behave well in low dimension
X = random_state.rand(laplacian.shape[0], n_components + 1)
X[:, 0] = dd.ravel()
lambdas, diffusion_map = lobpcg(laplacian,
X,
tol=1e-15,
largest=False,
maxiter=2000)
embedding = diffusion_map.T[:n_components]
if norm_laplacian:
embedding = embedding / dd
if embedding.shape[0] == 1:
raise ValueError
embedding = _deterministic_vector_sign_flip(embedding)
if drop_first:
return embedding[1:n_components].T
else:
return embedding[:n_components].T
def null_space(M, k, k_skip=1, eigen_solver='arpack', tol=1E-6, max_iter=100,
random_state=None):
"""
Find the null space of a matrix M.
Parameters
----------
M : array, matrix, sparse matrix, or LinearOperator
Input covariance matrix: should be symmetric positive semi-definite
k : number of eigenvalues/vectors to return
k_skip : number of low eigenvalues to skip.
eigen_solver : string ['arpack' | 'lobpcg' | 'dense']
arpack : use arnoldi iteration in shift-invert mode.
For this method, M may be a dense matrix, sparse matrix,
or general linear operator.
lobpcg : use locally optimized block-preconditioned conjugate gradient.
For this method, M may be a dense or sparse matrix.
A dense matrix M will be converted internally to a
csr sparse format.
dense : use standard dense matrix operations for the eigenvalue
decomposition. For this method, M must be an array
or matrix type. This method should be avoided for
large problems.
tol : tolerance for 'arpack' or 'lobpcg' methods.
not used if eigen_solver=='dense'
max_iter : maximum number of iterations for 'arpack' or 'lobpcg' methods
not used if eigen_solver=='dense'
"""
random_state = check_random_state(random_state)
if eigen_solver == 'arpack':
eigen_values, eigen_vectors = eigsh(M, k + k_skip, sigma=0.0,
tol=tol, maxiter=max_iter)
return eigen_vectors[:, k_skip:], np.sum(eigen_values[k_skip:])
elif eigen_solver == 'lobpcg':
# initial vectors for iteration
X = np.random.rand(M.shape[0], k + k_skip)
try:
ml = pyamg.smoothed_aggregation_solver(M, symmetry='symmetric')
except TypeError:
ml = pyamg.smoothed_aggregation_solver(M, mat_flag='symmetric')
prec = ml.aspreconditioner()
# compute eigenvalues and eigenvectors with LOBPCG
eigen_values, eigen_vectors = linalg.lobpcg(
M, X, M=prec, largest=False, tol=tol, maxiter=max_iter)
index = np.argsort(eigen_values)
return (eigen_vectors[:, index[k_skip:]],
np.sum(eigen_values[index[k_skip:]]))
elif eigen_solver == 'dense':
M = np.asarray(M)
eigen_values, eigen_vectors = eigh(
M, eigvals=(k_skip, k + k_skip), overwrite_a=True)
index = np.argsort(np.abs(eigen_values))
return eigen_vectors[:, index], np.sum(eigen_values)
else:
raise ValueError("Unrecognized eigen_solver '%s'" % eigen_solver)
def spectral_embedding(adjacency, k=8, mode=None):
""" Spectral embedding: project the sample on the k first
eigen vectors of the graph laplacian.
Parameters
-----------
adjacency: array-like or sparse matrix, shape: (p, p)
The adjacency matrix of the graph to embed.
k: integer, optional
The dimension of the projection subspace.
mode: {None, 'arpack' or 'amg'}
The eigenvalue decomposition strategy to use. AMG (Algebraic
MultiGrid) is much faster, but requires pyamg to be
installed.
Returns
--------
embedding: array, shape: (p, k)
The reduced samples
Notes
------
The graph should contain only one connect component,
elsewhere the results make little sens.
"""
from scipy import sparse
from scipy.sparse.linalg.eigen.arpack import eigen_symmetric
from scipy.sparse.linalg import lobpcg
try:
from pyamg import smoothed_aggregation_solver
amg_loaded = True
except ImportError:
amg_loaded = False
n_nodes = adjacency.shape[0]
# XXX: Should we check that the matrices given is symmetric
if not amg_loaded:
warnings.warn('pyamg not available, using scipy.sparse')
if mode is None:
mode = ('amg' if amg_loaded else 'arpack')
laplacian, dd = graph_laplacian(adjacency,
normed=True, return_diag=True)
if (mode == 'arpack'
or not sparse.isspmatrix(laplacian)
or n_nodes < 5*k # This is the threshold under which lobpcg has bugs
):
# We need to put the diagonal at zero
if not sparse.isspmatrix(laplacian):
laplacian[::n_nodes+1] = 0
else:
laplacian = laplacian.tocoo()
diag_idx = (laplacian.row == laplacian.col)
laplacian.data[diag_idx] = 0
# If the matrix has a small number of diagonals (as in the
# case of structured matrices comming from images), the
# dia format might be best suited for matvec products:
n_diags = np.unique(laplacian.row - laplacian.col).size
if n_diags <= 7:
# 3 or less outer diagonals on each side
laplacian = laplacian.todia()
else:
# csr has the fastest matvec and is thus best suited to
# arpack
laplacian = laplacian.tocsr()
lambdas, diffusion_map = eigen_symmetric(-laplacian, k=k, which='LA')
embedding = diffusion_map.T[::-1]*dd
elif mode == 'amg':
# Use AMG to get a preconditionner and speed up the eigenvalue
# problem.
laplacian = laplacian.astype(np.float) # lobpcg needs the native float
ml = smoothed_aggregation_solver(laplacian.tocsr())
X = np.random.rand(laplacian.shape[0], k)
X[:, 0] = 1. / dd.ravel()
M = ml.aspreconditioner()
lambdas, diffusion_map = lobpcg(laplacian, X, M=M, tol=1.e-12,
largest=False)
embedding = diffusion_map.T * dd
if embedding.shape[0] == 1: raise ValueError
else:
raise ValueError("Unknown value for mode: '%s'." % mode)
return embedding
def fem_laplacian(points, faces, spectrum_size=10, normalization=None):
"""
Compute linear finite-element method Laplace-Beltrami spectrum
after Martin Reuter's MATLAB code.
Note ::
Compare fem_laplacian() with Martin Reuter's Matlab eigenvalues:
fem_laplacian() results for Twins-2-1 left hemisphere (6 values):
[4.829758648026221e-18,
0.0001284173002467199,
0.0002715181572272745,
0.0003205150847159417,
0.0004701628070486448,
0.0005768904023010318]
Martin Reuter's shapeDNA-tria Matlab code:
{-4.7207711983791511358e-18 ;
0.00012841730024672144738 ;
0.00027151815722727096853 ;
0.00032051508471592313632 ;
0.0004701628070486902353 ;
0.00057689040230097490998 }
fem_laplacian() results for Twins-2-1 left postcentral (1022):
[6.3469513010430304e-18,
0.0005178862383467463,
0.0017434911095630772,
0.003667561767487686,
0.005429017880363784,
0.006309346984678924]
Martin Reuter's Matlab code:
{-2.1954862991027e-18 ;
0.0005178862383468 ;
0.0017434911095628 ;
0.0036675617674875 ;
0.0054290178803611 ;
0.006309346984678 }
Julien Lefevre, regarding comparison with Spongy results:
"I have done some comparisons between my Matlab codes and yours
on python and everything sounds perfect:
The evaluation has been done only for one mesh (about 10000 vertices)."
- L2 error between your A and B matrices and mine are about 1e-16.
- I have also compared eigenvalues of the generalized problem;
even if the error is slightly increasing, it remains on the order
of machine precision.
- Another good point: computation time for 1000 eigenvalues was 67s
with python versus 63s in matlab.
And it is quite the same behavior for lower orders.
- Since the eigenvalues are increasing with order,
it is also interesting to look at the relative error...
high frequencies are not so much perturbed."
Parameters
----------
points : list of lists of 3 floats
x,y,z coordinates for each vertex of the structure
faces : list of lists of 3 integers
3 indices to vertices that form a triangle on the mesh
spectrum_size : integer
number of eigenvalues to be computed (the length of the spectrum)
normalization : string
the method used to normalize eigenvalues ('area' or None)
if "area", use area of the 2D structure as in Reuter et al. 2006
Returns
-------
spectrum : list
first spectrum_size eigenvalues for Laplace-Beltrami spectrum
Examples
--------
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> # Define a cube:
>>> points = [[0,0,0], [0,1,0], [1,1,0], [1,0,0],
>>> [0,0,1], [0,1,1], [1,1,1], [1,0,1]]
>>> faces = [[0,1,2], [2,3,0], [4,5,6], [6,7,4], [0,4,7], [7,3,0],
>>> [0,4,5], [5,1,0], [1,5,6], [6,2,1], [3,7,6], [6,2,3]]
>>> fem_laplacian(points, faces, spectrum_size=3, normalization=None)
[7.401486830834377e-17, 4.58359213500127, 4.799999999999998]
>>> fem_laplacian(points, faces, spectrum_size=3, normalization="area")
[1.2335811384723967e-17, 0.76393202250021175, 0.79999999999999949]
>>> # Spectrum for entire left hemisphere of Twins-2-1:
>>> import os
>>> from mindboggle.mio.vtks import read_faces_points
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> path = os.environ['MINDBOGGLE_DATA']
>>> vtk_file = os.path.join(path, 'arno', 'labels',
>>> 'lh.labels.DKT25.manual.vtk')
>>> faces, points, npoints = read_faces_points(vtk_file)
>>> fem_laplacian(points, faces, spectrum_size=6, normalization=None)
[4.829758648026222e-18,
0.0001284173002467197,
0.000271518157227274,
0.00032051508471594065,
0.0004701628070486444,
0.0005768904023010318]
>>> # Spectrum for Twins-2-1 left postcentral pial surface (22):
>>> import os
>>> from mindboggle.mio.vtks import read_vtk
>>> from mindboggle.guts.mesh import remove_faces, reindex_faces_points
>>> from mindboggle.shapes.laplace_beltrami import fem_laplacian
>>> path = os.environ['MINDBOGGLE_DATA']
>>> label_file = os.path.join(path, 'arno', 'labels', 'lh.labels.DKT31.manual.vtk')
>>> faces, u1,u2, points, u3, labels, u4,u5 = read_vtk(label_file)
>>> I22 = [i for i,x in enumerate(labels) if x==22] # postcentral
>>> faces = remove_faces(faces, I22)
>>> faces, points, o1 = reindex_faces_points(faces, points)
>>> #from mindboggle.mio.vtks import read_faces_points
>>> #label_file = os.path.join(path, 'arno', 'labels', 'label22.vtk')
>>> #faces, points, npoints = read_faces_points(label_file)
>>> fem_laplacian(points, faces, spectrum_size=6, normalization=None)
[6.3469513010430304e-18,
0.0005178862383467462,
0.0017434911095630795,
0.0036675617674876856,
0.005429017880363785,
0.006309346984678933]
>>> # Area-normalized spectrum for a single label (postcentral):
>>> fem_laplacian(points, faces, spectrum_size=6, normalization="area")
[1.1410192787181146e-21,
9.3102680973672063e-08,
3.1343504525679647e-07,
6.5933366810380741e-07,
9.7599836081654446e-07,
1.1342589857996233e-06]
"""
from scipy.sparse.linalg import eigsh, lobpcg
import numpy as np
from mindboggle.shapes.laplace_beltrami import computeAB
#-----------------------------------------------------------------
# Compute A and B matrices (from Reuter et al., 2009):
#-----------------------------------------------------------------
A, B = computeAB(points, faces)
if A.shape[0] <= spectrum_size:
print("The 3D shape has too few vertices ({0} <= {1}). Skip.".
format(A.shape[0], spectrum_size))
return None
#-----------------------------------------------------------------
# Use the eigsh eigensolver:
#-----------------------------------------------------------------
try :
# eigs is for nonsymmetric matrices while
# eigsh is for real-symmetric or complex-Hermitian matrices:
eigenvalues, eigenvectors = eigsh(A, k=spectrum_size, M=B,
sigma=0)
spectrum = eigenvalues.tolist()
#-----------------------------------------------------------------
# Use the lobpcg eigensolver:
#-----------------------------------------------------------------
except RuntimeError:
print("eigsh() failed. Now try lobpcg.")
print("Warning: lobpcg can produce different results from "
"Reuter (2006) shapeDNA-tria software.")
# Initial eigenvector values:
init_eigenvecs = np.random.random((A.shape[0], spectrum_size))
# maxiter = 40 forces lobpcg to use 20 iterations.
# Strangely, largest=false finds largest eigenvalues
# and largest=True gives the smallest eigenvalues:
eigenvalues, eigenvectors = lobpcg(A, init_eigenvecs, B=B,
largest=True, maxiter=40)
# Extract the real parts:
spectrum = [value.real for value in eigenvalues]
# For some reason, the eigenvalues from lobpcg are not sorted:
spectrum.sort()
#-----------------------------------------------------------------
# Normalize by area:
#-----------------------------------------------------------------
if normalization == "area":
spectrum = area_normalize(points, faces, spectrum)
print("Compute area-normalized linear FEM Laplace-Beltrami spectrum")
else:
print("Compute linear FEM Laplace-Beltrami spectrum")
return spectrum
def MyDataset(dataset, Lev, s, n, FrameType='Haar', add_feature=False, QM7=False):
if FrameType == 'Haar':
D1 = lambda x: np.cos(x / 2)
D2 = lambda x: np.sin(x / 2)
DFilters = [D1, D2]
elif FrameType == 'Linear':
D1 = lambda x: np.square(np.cos(x / 2))
D2 = lambda x: np.sin(x) / np.sqrt(2)
D3 = lambda x: np.square(np.sin(x / 2))
DFilters = [D1, D2, D3]
elif FrameType == 'Quadratic': # not accurate so far
D1 = lambda x: np.cos(x / 2) ** 3
D2 = lambda x: np.multiply((np.sqrt(3) * np.sin(x / 2)), np.cos(x / 2) ** 2)
D3 = lambda x: np.multiply((np.sqrt(3) * np.sin(x / 2) ** 2), np.cos(x / 2))
D4 = lambda x: np.sin(x / 2) ** 3
DFilters = [D1, D2, D3, D4]
else:
raise Exception('Invalid FrameType')
r = len(DFilters)
dataset1 = list()
label=list()
for i in range(len(dataset)):
if add_feature:
raise Exception('this function has not been completed') # will add this function as required
else:
if QM7:
x_qm7 = torch.ones(dataset[i].num_nodes, num_features)
data1 = Data(x=x_qm7, edge_index=dataset[i].edge_index, y=dataset[i].y)
data1.y_origin = dataset[i].y_origin
else:
data1 = Data(x=dataset[i].x, edge_index=dataset[i].edge_index, y=dataset[i].y)
if QM7:
label.append(dataset[i].y_origin)
# get graph Laplacian
num_nodes = data1.x.shape[0]
L = get_laplacian(dataset[i].edge_index, num_nodes=num_nodes, normalization='sym')
L = sparse.coo_matrix((L[1].numpy(), (L[0][0, :].numpy(), L[0][1, :].numpy())), shape=(num_nodes, num_nodes))
# calculate lambda max
lobpcg_init = np.random.rand(num_nodes, 1)
lambda_max, _ = lobpcg(L, lobpcg_init)
lambda_max = lambda_max[0]
J = np.log(lambda_max / np.pi) / np.log(s) + Lev - 1 # dilation level to start the decomposition
# get matrix operators
d = get_operator(L, DFilters, n, s, J, Lev)
for m in range(1, r):
for q in range(Lev):
if (m == 1) and (q == 0):
d_aggre = d[m, q]
else:
d_aggre = sparse.vstack((d_aggre, d[m, q]))
d_aggre = sparse.vstack((d[0, Lev - 1], d_aggre)) ###stack the n x n matrix
data1.d = [d_aggre]
# get d_index
a = [i for i in range((r - 1) * Lev + 1)]##len=3
data1.d_index=[[a[i // num_nodes] for i in range(len(a) * num_nodes)]]##3*num [0,1,2;,0,1,2...]
# append data1 into dataset1
dataset1.append(data1)
if QM7:
mean = torch.mean(torch.Tensor(label)).item()
std = torch.sqrt(torch.var(torch.Tensor(label))).item()
return dataset1, r, mean, std
else:
return dataset1, r
def spectral_embedding(adjacency, n_components=8, mode=None,
random_state=None, eig_tol=0.0):
"""Project the sample on the first eigen vectors of the graph Laplacian
The adjacency matrix is used to compute a normalized graph Laplacian
whose spectrum (especially the eigen vectors associated to the
smallest eigen values) has an interpretation in terms of minimal
number of cuts necessary to split the graph into comparably sized
components.
This embedding can also 'work' even if the ``adjacency`` variable is
not strictly the adjacency matrix of a graph but more generally
an affinity or similarity matrix between samples (for instance the
heat kernel of a euclidean distance matrix or a k-NN matrix).
However care must taken to always make the affinity matrix symmetric
so that the eigen vector decomposition works as expected.
Parameters
----------
adjacency: array-like or sparse matrix, shape: (n_samples, n_samples)
The adjacency matrix of the graph to embed.
n_components: integer, optional
The dimension of the projection subspace.
mode: {None, 'arpack', 'lobpcg', or 'amg'}
The eigenvalue decomposition strategy to use. AMG requires pyamg
to be installed. It can be faster on very large, sparse problems,
but may also lead to instabilities
random_state: int seed, RandomState instance, or None (default)
A pseudo random number generator used for the initialization of the
lobpcg eigen vectors decomposition when mode == 'amg'. By default
arpack is used.
eig_tol : float, optional, default: 0.0
Stopping criterion for eigendecomposition of the Laplacian matrix
when using arpack mode.
Returns
-------
embedding: array, shape: (n_samples, n_components)
The reduced samples
Notes
-----
The graph should contain only one connected component, elsewhere the
results make little sense.
References
----------
[1] http://en.wikipedia.org/wiki/LOBPCG
[2] LOBPCG: http://dx.doi.org/10.1137%2FS1064827500366124
"""
from scipy import sparse
from ..utils.arpack import eigsh
from scipy.sparse.linalg import lobpcg
from scipy.sparse.linalg.eigen.lobpcg.lobpcg import symeig
try:
from pyamg import smoothed_aggregation_solver
except ImportError:
if mode == "amg":
raise ValueError("The mode was set to 'amg', but pyamg is "
"not available.")
random_state = check_random_state(random_state)
n_nodes = adjacency.shape[0]
# XXX: Should we check that the matrices given is symmetric
if mode is None:
mode = 'arpack'
elif not mode in ('arpack', 'lobpcg', 'amg'):
raise ValueError("Unknown value for mode: '%s'."
"Should be 'amg', 'arpack', or 'lobpcg'" % mode)
laplacian, dd = graph_laplacian(adjacency,
normed=True, return_diag=True)
if (mode == 'arpack'
or mode != 'lobpcg' and
(not sparse.isspmatrix(laplacian)
or n_nodes < 5 * n_components)):
# lobpcg used with mode='amg' has bugs for low number of nodes
# for details see the source code in scipy:
# https://github.com/scipy/scipy/blob/v0.11.0/scipy/sparse/linalg/eigen/lobpcg/lobpcg.py#L237
# or matlab:
# http://www.mathworks.com/matlabcentral/fileexchange/48-lobpcg-m
laplacian = _set_diag(laplacian, 0)
# Here we'll use shift-invert mode for fast eigenvalues
# (see http://docs.scipy.org/doc/scipy/reference/tutorial/arpack.html
# for a short explanation of what this means)
# Because the normalized Laplacian has eigenvalues between 0 and 2,
# I - L has eigenvalues between -1 and 1. ARPACK is most efficient
# when finding eigenvalues of largest magnitude (keyword which='LM')
# and when these eigenvalues are very large compared to the rest.
# For very large, very sparse graphs, I - L can have many, many
# eigenvalues very near 1.0. This leads to slow convergence. So
# instead, we'll use ARPACK's shift-invert mode, asking for the
# eigenvalues near 1.0. This effectively spreads-out the spectrum
# near 1.0 and leads to much faster convergence: potentially an
# orders-of-magnitude speedup over simply using keyword which='LA'
# in standard mode.
try:
lambdas, diffusion_map = eigsh(-laplacian, k=n_components,
sigma=1.0, which='LM',
tol=eig_tol)
embedding = diffusion_map.T[::-1] * dd
except RuntimeError:
# When submatrices are exactly singular, an LU decomposition
# in arpack fails. We fallback to lobpcg
mode = "lobpcg"
if mode == 'amg':
# Use AMG to get a preconditioner and speed up the eigenvalue
# problem.
laplacian = laplacian.astype(np.float) # lobpcg needs native floats
ml = smoothed_aggregation_solver(laplacian.tocsr())
M = ml.aspreconditioner()
X = random_state.rand(laplacian.shape[0], n_components)
X[:, 0] = dd.ravel()
lambdas, diffusion_map = lobpcg(laplacian, X, M=M, tol=1.e-12,
largest=False)
embedding = diffusion_map.T * dd
if embedding.shape[0] == 1:
raise ValueError
elif mode == "lobpcg":
laplacian = laplacian.astype(np.float) # lobpcg needs native floats
if n_nodes < 5 * n_components + 1:
# see note above under arpack why lopbcg has problems with small
# number of nodes
# lobpcg will fallback to symeig, so we short circuit it
if sparse.isspmatrix(laplacian):
laplacian = laplacian.todense()
lambdas, diffusion_map = symeig(laplacian)
embedding = diffusion_map.T[:n_components] * dd
else:
# lobpcg needs native floats
laplacian = laplacian.astype(np.float)
laplacian = _set_diag(laplacian, 1)
# We increase the number of eigenvectors requested, as lobpcg
# doesn't behave well in low dimension
X = random_state.rand(laplacian.shape[0], n_components + 1)
X[:, 0] = dd.ravel()
lambdas, diffusion_map = lobpcg(laplacian, X, tol=1e-15,
largest=False, maxiter=2000)
embedding = diffusion_map.T[:n_components] * dd
if embedding.shape[0] == 1:
raise ValueError
return embedding