def bicg(A, b, x0=None, tol=1e-5, maxiter=None, xtype=None, M=None, callback=None):
A,M,x,b,postprocess = make_system(A,M,x0,b,xtype)
n = len(b)
if maxiter is None:
maxiter = n*10
matvec, rmatvec = A.matvec, A.rmatvec
psolve, rpsolve = M.matvec, M.rmatvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'bicgrevcom')
stoptest = getattr(_iterative, ltr + 'stoptest2')
resid = tol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(6*n,dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
bnrm2 = -1.0
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1*rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = psolve(work[slice2])
elif (ijob == 4):
work[slice1] = rpsolve(work[slice2])
elif (ijob == 5):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(x)
elif (ijob == 6):
if ftflag:
info = -1
ftflag = False
bnrm2, resid, info = stoptest(work[slice1], b, bnrm2, tol, info)
ijob = 2
if info > 0 and iter_ == maxiter and resid > tol:
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def bicgstab(A, b, x0=None, tol=1e-5, maxiter=None, M=None, callback=None, atol=None):
A, M, x, b, postprocess = make_system(A, M, x0, b)
n = len(b)
if maxiter is None:
maxiter = n*10
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'bicgstabrevcom')
get_residual = lambda: np.linalg.norm(matvec(x) - b)
atol = _get_atol(tol, atol, np.linalg.norm(b), get_residual, 'bicgstab')
if atol == 'exit':
return postprocess(x), 0
resid = atol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(7*n,dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(work[slice1])
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(x)
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
ijob = 2
if info > 0 and iter_ == maxiter and not (resid <= atol):
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def check(shape, dtype, order, align):
err_msg = repr((shape, dtype, order, align))
x = _aligned_zeros(shape, dtype, order, align=align)
if align is None:
align = np.dtype(dtype).alignment
assert_equal(x.__array_interface__['data'][0] % align, 0)
if hasattr(shape, '__len__'):
assert_equal(x.shape, shape, err_msg)
else:
assert_equal(x.shape, (shape,), err_msg)
assert_equal(x.dtype, dtype)
if order == "C":
assert_(x.flags.c_contiguous, err_msg)
elif order == "F":
if x.size > 0:
# Size-0 arrays get invalid flags on Numpy 1.5
assert_(x.flags.f_contiguous, err_msg)
elif order is None:
assert_(x.flags.c_contiguous, err_msg)
else:
raise ValueError()
def check(shape, dtype, order, align):
err_msg = repr((shape, dtype, order, align))
x = _aligned_zeros(shape, dtype, order, align=align)
if align is None:
align = np.dtype(dtype).alignment
assert_equal(x.__array_interface__['data'][0] % align, 0)
if hasattr(shape, '__len__'):
assert_equal(x.shape, shape, err_msg)
else:
assert_equal(x.shape, (shape, ), err_msg)
assert_equal(x.dtype, dtype)
if order == "C":
assert_(x.flags.c_contiguous, err_msg)
elif order == "F":
if x.size > 0:
# Size-0 arrays get invalid flags on Numpy 1.5
assert_(x.flags.f_contiguous, err_msg)
elif order is None:
assert_(x.flags.c_contiguous, err_msg)
else:
raise ValueError()
def gmres(A,
b,
x0=None,
tol=1e-5,
restart=None,
maxiter=None,
M=None,
callback=None,
restrt=None,
atol=None,
callback_type=None):
"""
Use Generalized Minimal RESidual iteration to solve ``Ax = b``.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real or complex N-by-N matrix of the linear system.
Alternatively, ``A`` can be a linear operator which can
produce ``Ax`` using, e.g.,
``scipy.sparse.linalg.LinearOperator``.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : int
Provides convergence information:
* 0 : successful exit
* >0 : convergence to tolerance not achieved, number of iterations
* <0 : illegal input or breakdown
Other parameters
----------------
x0 : {array, matrix}
Starting guess for the solution (a vector of zeros by default).
tol, atol : float, optional
Tolerances for convergence, ``norm(residual) <= max(tol*norm(b), atol)``.
The default for ``atol`` is ``'legacy'``, which emulates
a different legacy behavior.
.. warning::
The default value for `atol` will be changed in a future release.
For future compatibility, specify `atol` explicitly.
restart : int, optional
Number of iterations between restarts. Larger values increase
iteration cost, but may be necessary for convergence.
Default is 20.
maxiter : int, optional
Maximum number of iterations (restart cycles). Iteration will stop
after maxiter steps even if the specified tolerance has not been
achieved.
M : {sparse matrix, dense matrix, LinearOperator}
Inverse of the preconditioner of A. M should approximate the
inverse of A and be easy to solve for (see Notes). Effective
preconditioning dramatically improves the rate of convergence,
which implies that fewer iterations are needed to reach a given
error tolerance. By default, no preconditioner is used.
callback : function
User-supplied function to call after each iteration. It is called
as `callback(args)`, where `args` are selected by `callback_type`.
callback_type : {'x', 'pr_norm', 'legacy'}, optional
Callback function argument requested:
- ``x``: current iterate (ndarray), called on every restart
- ``pr_norm``: relative (preconditioned) residual norm (float),
called on every inner iteration
- ``legacy`` (default): same as ``pr_norm``, but also changes the
meaning of 'maxiter' to count inner iterations instead of restart
cycles.
restrt : int, optional
DEPRECATED - use `restart` instead.
See Also
--------
LinearOperator
Notes
-----
A preconditioner, P, is chosen such that P is close to A but easy to solve
for. The preconditioner parameter required by this routine is
``M = P^-1``. The inverse should preferably not be calculated
explicitly. Rather, use the following template to produce M::
# Construct a linear operator that computes P^-1 * x.
import scipy.sparse.linalg as spla
M_x = lambda x: spla.spsolve(P, x)
M = spla.LinearOperator((n, n), M_x)
Examples
--------
>>> from scipy.sparse import csc_matrix
>>> from scipy.sparse.linalg import gmres
>>> A = csc_matrix([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = gmres(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
"""
# Change 'restrt' keyword to 'restart'
if restrt is None:
restrt = restart
elif restart is not None:
raise ValueError("Cannot specify both restart and restrt keywords. "
"Preferably use 'restart' only.")
if callback is not None and callback_type is None:
# Warn about 'callback_type' semantic changes.
# Probably should be removed only in far future, Scipy 2.0 or so.
warnings.warn(
"scipy.sparse.linalg.gmres called without specifying `callback_type`. "
"The default value will be changed in a future release. "
"For compatibility, specify a value for `callback_type` explicitly, e.g., "
"``{name}(..., callback_type='pr_norm')``, or to retain the old behavior "
"``{name}(..., callback_type='legacy')``",
category=DeprecationWarning,
stacklevel=3)
if callback_type is None:
callback_type = 'legacy'
if callback_type not in ('x', 'pr_norm', 'legacy'):
raise ValueError("Unknown callback_type: {!r}".format(callback_type))
if callback is None:
callback_type = 'none'
A, M, x, b, postprocess = make_system(A, M, x0, b)
n = len(b)
if maxiter is None:
maxiter = n * 10
if restrt is None:
restrt = 20
restrt = min(restrt, n)
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'gmresrevcom')
bnrm2 = np.linalg.norm(b)
Mb_nrm2 = np.linalg.norm(psolve(b))
get_residual = lambda: np.linalg.norm(matvec(x) - b)
atol = _get_atol(tol, atol, bnrm2, get_residual, 'gmres')
if atol == 'exit':
return postprocess(x), 0
if bnrm2 == 0:
return postprocess(b), 0
# Tolerance passed to GMRESREVCOM applies to the inner iteration
# and deals with the left-preconditioned residual.
ptol_max_factor = 1.0
ptol = Mb_nrm2 * min(ptol_max_factor, atol / bnrm2)
resid = np.nan
presid = np.nan
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros((6 + restrt) * n, dtype=x.dtype)
work2 = _aligned_zeros((restrt + 1) * (2 * restrt + 2), dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
old_ijob = ijob
first_pass = True
resid_ready = False
iter_num = 1
while True:
olditer = iter_
x, iter_, presid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, restrt, work, work2, iter_, presid, info, ndx1, ndx2, ijob, ptol)
if callback_type == 'x' and iter_ != olditer:
callback(x)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1): # gmres success, update last residual
if callback_type in ('pr_norm', 'legacy'):
if resid_ready:
callback(presid / bnrm2)
elif callback_type == 'x':
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(x)
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
if not first_pass and old_ijob == 3:
resid_ready = True
first_pass = False
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(work[slice1])
if resid_ready:
if callback_type in ('pr_norm', 'legacy'):
callback(presid / bnrm2)
resid_ready = False
iter_num = iter_num + 1
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
# Inner loop tolerance control
if info or presid > ptol:
ptol_max_factor = min(1.0, 1.5 * ptol_max_factor)
else:
# Inner loop tolerance OK, but outer loop not.
ptol_max_factor = max(1e-16, 0.25 * ptol_max_factor)
if resid != 0:
ptol = presid * min(ptol_max_factor, atol / resid)
else:
ptol = presid * ptol_max_factor
old_ijob = ijob
ijob = 2
if callback_type == 'legacy':
# Legacy behavior
if iter_num > maxiter:
info = maxiter
break
if info >= 0 and not (resid <= atol):
# info isn't set appropriately otherwise
info = maxiter
return postprocess(x), info
def cgs(A,
b,
x0=None,
tol=1e-5,
maxiter=None,
M=None,
callback=None,
atol=None):
A, M, x, b, postprocess = make_system(A, M, x0, b)
n = len(b)
if maxiter is None:
maxiter = n * 10
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'cgsrevcom')
get_residual = lambda: np.linalg.norm(matvec(x) - b)
atol = _get_atol(tol, atol, np.linalg.norm(b), get_residual, 'cgs')
if atol == 'exit':
return postprocess(x), 0
resid = atol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(7 * n, dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(work[slice1])
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(x)
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
if info == 1 and iter_ > 1:
# recompute residual and recheck, to avoid
# accumulating rounding error
work[slice1] = b - matvec(x)
resid, info = _stoptest(work[slice1], atol)
ijob = 2
if info == -10:
# termination due to breakdown: check for convergence
resid, ok = _stoptest(b - matvec(x), atol)
if ok:
info = 0
if info > 0 and iter_ == maxiter and not (resid <= atol):
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def bicg(A,
b,
x0=None,
tol=1e-5,
maxiter=None,
M=None,
callback=None,
atol=None):
A, M, x, b, postprocess = make_system(A, M, x0, b)
n = len(b)
if maxiter is None:
maxiter = n * 10
matvec, rmatvec = A.matvec, A.rmatvec
psolve, rpsolve = M.matvec, M.rmatvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'bicgrevcom')
get_residual = lambda: np.linalg.norm(matvec(x) - b)
atol = _get_atol(tol, atol, np.linalg.norm(b), get_residual, 'bicg')
if atol == 'exit':
return postprocess(x), 0
resid = atol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(6 * n, dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1 * rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = psolve(work[slice2])
elif (ijob == 4):
work[slice1] = rpsolve(work[slice2])
elif (ijob == 5):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(x)
elif (ijob == 6):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
ijob = 2
if info > 0 and iter_ == maxiter and not (resid <= atol):
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def qmr(A, b, x0=None, tol=1e-5, maxiter=None, xtype=None, M1=None, M2=None, callback=None):
"""Use Quasi-Minimal Residual iteration to solve A x = b
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real-valued N-by-N matrix of the linear system.
It is required that the linear operator can produce
``Ax`` and ``A^T x``.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : integer
Provides convergence information:
0 : successful exit
>0 : convergence to tolerance not achieved, number of iterations
<0 : illegal input or breakdown
Other Parameters
----------------
x0 : {array, matrix}
Starting guess for the solution.
tol : float
Tolerance to achieve. The algorithm terminates when either the relative
or the absolute residual is below `tol`.
maxiter : integer
Maximum number of iterations. Iteration will stop after maxiter
steps even if the specified tolerance has not been achieved.
M1 : {sparse matrix, dense matrix, LinearOperator}
Left preconditioner for A.
M2 : {sparse matrix, dense matrix, LinearOperator}
Right preconditioner for A. Used together with the left
preconditioner M1. The matrix M1*A*M2 should have better
conditioned than A alone.
callback : function
User-supplied function to call after each iteration. It is called
as callback(xk), where xk is the current solution vector.
xtype : {'f','d','F','D'}
This parameter is DEPRECATED -- avoid using it.
The type of the result. If None, then it will be determined from
A.dtype.char and b. If A does not have a typecode method then it
will compute A.matvec(x0) to get a typecode. To save the extra
computation when A does not have a typecode attribute use xtype=0
for the same type as b or use xtype='f','d','F',or 'D'.
This parameter has been superseded by LinearOperator.
See Also
--------
LinearOperator
"""
A_ = A
A,M,x,b,postprocess = make_system(A,None,x0,b,xtype)
if M1 is None and M2 is None:
if hasattr(A_,'psolve'):
def left_psolve(b):
return A_.psolve(b,'left')
def right_psolve(b):
return A_.psolve(b,'right')
def left_rpsolve(b):
return A_.rpsolve(b,'left')
def right_rpsolve(b):
return A_.rpsolve(b,'right')
M1 = LinearOperator(A.shape, matvec=left_psolve, rmatvec=left_rpsolve)
M2 = LinearOperator(A.shape, matvec=right_psolve, rmatvec=right_rpsolve)
else:
def id(b):
return b
M1 = LinearOperator(A.shape, matvec=id, rmatvec=id)
M2 = LinearOperator(A.shape, matvec=id, rmatvec=id)
n = len(b)
if maxiter is None:
maxiter = n*10
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'qmrrevcom')
stoptest = getattr(_iterative, ltr + 'stoptest2')
resid = tol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(11*n,x.dtype)
ijob = 1
info = 0
ftflag = True
bnrm2 = -1.0
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*A.matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1*A.rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = M1.matvec(work[slice2])
elif (ijob == 4):
work[slice1] = M2.matvec(work[slice2])
elif (ijob == 5):
work[slice1] = M1.rmatvec(work[slice2])
elif (ijob == 6):
work[slice1] = M2.rmatvec(work[slice2])
elif (ijob == 7):
work[slice2] *= sclr2
work[slice2] += sclr1*A.matvec(x)
elif (ijob == 8):
if ftflag:
info = -1
ftflag = False
bnrm2, resid, info = stoptest(work[slice1], b, bnrm2, tol, info)
ijob = 2
if info > 0 and iter_ == maxiter and resid > tol:
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def gmres(A, b, x0=None, tol=1e-5, restart=None, maxiter=None, xtype=None, M=None, callback=None, restrt=None):
"""
Use Generalized Minimal RESidual iteration to solve A x = b.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real or complex N-by-N matrix of the linear system.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : int
Provides convergence information:
* 0 : successful exit
* >0 : convergence to tolerance not achieved, number of iterations
* <0 : illegal input or breakdown
Other parameters
----------------
x0 : {array, matrix}
Starting guess for the solution (a vector of zeros by default).
tol : float
Tolerance to achieve. The algorithm terminates when either the relative
or the absolute residual is below `tol`.
restart : int, optional
Number of iterations between restarts. Larger values increase
iteration cost, but may be necessary for convergence.
Default is 20.
maxiter : int, optional
Maximum number of iterations (restart cycles). Iteration will stop
after maxiter steps even if the specified tolerance has not been
achieved.
xtype : {'f','d','F','D'}
This parameter is DEPRECATED --- avoid using it.
The type of the result. If None, then it will be determined from
A.dtype.char and b. If A does not have a typecode method then it
will compute A.matvec(x0) to get a typecode. To save the extra
computation when A does not have a typecode attribute use xtype=0
for the same type as b or use xtype='f','d','F',or 'D'.
This parameter has been superseded by LinearOperator.
M : {sparse matrix, dense matrix, LinearOperator}
Inverse of the preconditioner of A. M should approximate the
inverse of A and be easy to solve for (see Notes). Effective
preconditioning dramatically improves the rate of convergence,
which implies that fewer iterations are needed to reach a given
error tolerance. By default, no preconditioner is used.
callback : function
User-supplied function to call after each iteration. It is called
as callback(rk), where rk is the current residual vector.
restrt : int, optional
DEPRECATED - use `restart` instead.
See Also
--------
LinearOperator
Notes
-----
A preconditioner, P, is chosen such that P is close to A but easy to solve
for. The preconditioner parameter required by this routine is
``M = P^-1``. The inverse should preferably not be calculated
explicitly. Rather, use the following template to produce M::
# Construct a linear operator that computes P^-1 * x.
import scipy.sparse.linalg as spla
M_x = lambda x: spla.spsolve(P, x)
M = spla.LinearOperator((n, n), M_x)
"""
# Change 'restrt' keyword to 'restart'
if restrt is None:
restrt = restart
elif restart is not None:
raise ValueError("Cannot specify both restart and restrt keywords. "
"Preferably use 'restart' only.")
A,M,x,b,postprocess = make_system(A,M,x0,b,xtype)
n = len(b)
if maxiter is None:
maxiter = n*10
if restrt is None:
restrt = 20
restrt = min(restrt, n)
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'gmresrevcom')
stoptest = getattr(_iterative, ltr + 'stoptest2')
resid = tol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros((6+restrt)*n,dtype=x.dtype)
work2 = _aligned_zeros((restrt+1)*(2*restrt+2),dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
bnrm2 = -1.0
iter_ = maxiter
old_ijob = ijob
first_pass = True
resid_ready = False
iter_num = 1
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, restrt, work, work2, iter_, resid, info, ndx1, ndx2, ijob)
# if callback is not None and iter_ > olditer:
# callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1): # gmres success, update last residual
if resid_ready and callback is not None:
callback(resid)
resid_ready = False
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(x)
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
if not first_pass and old_ijob == 3:
resid_ready = True
first_pass = False
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(work[slice1])
if resid_ready and callback is not None:
callback(resid)
resid_ready = False
iter_num = iter_num+1
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
bnrm2, resid, info = stoptest(work[slice1], b, bnrm2, tol, info)
old_ijob = ijob
ijob = 2
if iter_num > maxiter:
break
if info >= 0 and resid > tol:
# info isn't set appropriately otherwise
info = maxiter
return postprocess(x), info
def __init__(self,
n,
k,
tp,
matvec,
mode=1,
M_matvec=None,
Minv_matvec=None,
sigma=None,
ncv=None,
v0=None,
maxiter=None,
which="LM",
tol=0):
# The following modes are supported:
# mode = 1:
# Solve the standard eigenvalue problem:
# A*x = lambda*x :
# A - symmetric
# Arguments should be
# matvec = left multiplication by A
# M_matvec = None [not used]
# Minv_matvec = None [not used]
#
# mode = 2:
# Solve the general eigenvalue problem:
# A*x = lambda*M*x
# A - symmetric
# M - symmetric positive definite
# Arguments should be
# matvec = left multiplication by A
# M_matvec = left multiplication by M
# Minv_matvec = left multiplication by M^-1
#
# mode = 3:
# Solve the general eigenvalue problem in shift-invert mode:
# A*x = lambda*M*x
# A - symmetric
# M - symmetric positive semi-definite
# Arguments should be
# matvec = None [not used]
# M_matvec = left multiplication by M
# or None, if M is the identity
# Minv_matvec = left multiplication by [A-sigma*M]^-1
#
# mode = 4:
# Solve the general eigenvalue problem in Buckling mode:
# A*x = lambda*AG*x
# A - symmetric positive semi-definite
# AG - symmetric indefinite
# Arguments should be
# matvec = left multiplication by A
# M_matvec = None [not used]
# Minv_matvec = left multiplication by [A-sigma*AG]^-1
#
# mode = 5:
# Solve the general eigenvalue problem in Cayley-transformed mode:
# A*x = lambda*M*x
# A - symmetric
# M - symmetric positive semi-definite
# Arguments should be
# matvec = left multiplication by A
# M_matvec = left multiplication by M
# or None, if M is the identity
# Minv_matvec = left multiplication by [A-sigma*M]^-1
if mode == 1:
if matvec is None:
raise ValueError("matvec must be specified for mode=1")
if M_matvec is not None:
raise ValueError("M_matvec cannot be specified for mode=1")
if Minv_matvec is not None:
raise ValueError("Minv_matvec cannot be specified for mode=1")
self.OP = matvec
self.B = lambda x: x
self.bmat = "I"
elif mode == 2:
if matvec is None:
raise ValueError("matvec must be specified for mode=2")
if M_matvec is None:
raise ValueError("M_matvec must be specified for mode=2")
if Minv_matvec is None:
raise ValueError("Minv_matvec must be specified for mode=2")
self.OP = lambda x: Minv_matvec(matvec(x))
self.OPa = Minv_matvec
self.OPb = matvec
self.B = M_matvec
self.bmat = "G"
elif mode == 3:
if matvec is not None:
raise ValueError("matvec must not be specified for mode=3")
if Minv_matvec is None:
raise ValueError("Minv_matvec must be specified for mode=3")
if M_matvec is None:
self.OP = Minv_matvec
self.OPa = Minv_matvec
self.B = lambda x: x
self.bmat = "I"
else:
self.OP = lambda x: Minv_matvec(M_matvec(x))
self.OPa = Minv_matvec
self.B = M_matvec
self.bmat = "G"
elif mode == 4:
if matvec is None:
raise ValueError("matvec must be specified for mode=4")
if M_matvec is not None:
raise ValueError("M_matvec must not be specified for mode=4")
if Minv_matvec is None:
raise ValueError("Minv_matvec must be specified for mode=4")
self.OPa = Minv_matvec
self.OP = lambda x: self.OPa(matvec(x))
self.B = matvec
self.bmat = "G"
elif mode == 5:
if matvec is None:
raise ValueError("matvec must be specified for mode=5")
if Minv_matvec is None:
raise ValueError("Minv_matvec must be specified for mode=5")
self.OPa = Minv_matvec
self.A_matvec = matvec
if M_matvec is None:
self.OP = lambda x: Minv_matvec(matvec(x) + sigma * x)
self.B = lambda x: x
self.bmat = "I"
else:
self.OP = lambda x: Minv_matvec(matvec(x) + sigma * M_matvec(x))
self.B = M_matvec
self.bmat = "G"
else:
raise ValueError("mode=%i not implemented" % mode)
if which not in _SEUPD_WHICH:
raise ValueError("which must be one of %s" % " ".join(_SEUPD_WHICH))
if k >= n:
raise ValueError("k must be less than ndim(A), k=%d" % k)
_ArpackParams.__init__(self, n, k, tp, mode, sigma, ncv, v0, maxiter, which,
tol)
if self.ncv > n or self.ncv <= k:
raise ValueError("ncv must be k<ncv<=n, ncv=%s" % self.ncv)
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
self.workd = _aligned_zeros(3 * n, self.tp)
self.workl = _aligned_zeros(self.ncv * (self.ncv + 8), self.tp)
ltr = _type_conv[self.tp]
if ltr not in ["s", "d"]:
raise ValueError("Input matrix is not real-valued.")
self._arpack_solver = _arpack.__dict__[ltr + "saupd"]
self._arpack_extract = _arpack.__dict__[ltr + "seupd"]
self.iterate_infodict = _SAUPD_ERRORS[ltr]
self.extract_infodict = _SEUPD_ERRORS[ltr]
self.ipntr = np.zeros(11, "int")
def gmres(A, b, x0=None, tol=1e-5, restart=None, maxiter=None, M=None, callback=None,
restrt=None, atol=None):
"""
Use Generalized Minimal RESidual iteration to solve ``Ax = b``.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real or complex N-by-N matrix of the linear system.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : int
Provides convergence information:
* 0 : successful exit
* >0 : convergence to tolerance not achieved, number of iterations
* <0 : illegal input or breakdown
Other parameters
----------------
x0 : {array, matrix}
Starting guess for the solution (a vector of zeros by default).
tol, atol : float, optional
Tolerances for convergence, ``norm(residual) <= max(tol*norm(b), atol)``.
The default for ``atol`` is ``'legacy'``, which emulates
a different legacy behavior.
.. warning::
The default value for `atol` will be changed in a future release.
For future compatibility, specify `atol` explicitly.
restart : int, optional
Number of iterations between restarts. Larger values increase
iteration cost, but may be necessary for convergence.
Default is 20.
maxiter : int, optional
Maximum number of iterations (restart cycles). Iteration will stop
after maxiter steps even if the specified tolerance has not been
achieved.
M : {sparse matrix, dense matrix, LinearOperator}
Inverse of the preconditioner of A. M should approximate the
inverse of A and be easy to solve for (see Notes). Effective
preconditioning dramatically improves the rate of convergence,
which implies that fewer iterations are needed to reach a given
error tolerance. By default, no preconditioner is used.
callback : function
User-supplied function to call after each iteration. It is called
as callback(rk), where rk is the current residual vector.
restrt : int, optional
DEPRECATED - use `restart` instead.
See Also
--------
LinearOperator
Notes
-----
A preconditioner, P, is chosen such that P is close to A but easy to solve
for. The preconditioner parameter required by this routine is
``M = P^-1``. The inverse should preferably not be calculated
explicitly. Rather, use the following template to produce M::
# Construct a linear operator that computes P^-1 * x.
import scipy.sparse.linalg as spla
M_x = lambda x: spla.spsolve(P, x)
M = spla.LinearOperator((n, n), M_x)
Examples
--------
>>> from scipy.sparse import csc_matrix
>>> from scipy.sparse.linalg import gmres
>>> A = csc_matrix([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = gmres(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
"""
# Change 'restrt' keyword to 'restart'
if restrt is None:
restrt = restart
elif restart is not None:
raise ValueError("Cannot specify both restart and restrt keywords. "
"Preferably use 'restart' only.")
A, M, x, b,postprocess = make_system(A, M, x0, b)
n = len(b)
if maxiter is None:
maxiter = n*10
if restrt is None:
restrt = 20
restrt = min(restrt, n)
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'gmresrevcom')
bnrm2 = np.linalg.norm(b)
Mb_nrm2 = np.linalg.norm(psolve(b))
get_residual = lambda: np.linalg.norm(matvec(x) - b)
atol = _get_atol(tol, atol, bnrm2, get_residual, 'gmres')
if atol == 'exit':
return postprocess(x), 0
if bnrm2 == 0:
return postprocess(b), 0
# Tolerance passed to GMRESREVCOM applies to the inner iteration
# and deals with the left-preconditioned residual.
ptol_max_factor = 1.0
ptol = Mb_nrm2 * min(ptol_max_factor, atol / bnrm2)
resid = np.nan
presid = np.nan
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros((6+restrt)*n,dtype=x.dtype)
work2 = _aligned_zeros((restrt+1)*(2*restrt+2),dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
old_ijob = ijob
first_pass = True
resid_ready = False
iter_num = 1
while True:
x, iter_, presid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, restrt, work, work2, iter_, presid, info, ndx1, ndx2, ijob, ptol)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1): # gmres success, update last residual
if resid_ready and callback is not None:
callback(presid / bnrm2)
resid_ready = False
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(x)
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
if not first_pass and old_ijob == 3:
resid_ready = True
first_pass = False
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(work[slice1])
if resid_ready and callback is not None:
callback(presid / bnrm2)
resid_ready = False
iter_num = iter_num+1
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
# Inner loop tolerance control
if info or presid > ptol:
ptol_max_factor = min(1.0, 1.5 * ptol_max_factor)
else:
# Inner loop tolerance OK, but outer loop not.
ptol_max_factor = max(1e-16, 0.25 * ptol_max_factor)
if resid != 0:
ptol = presid * min(ptol_max_factor, atol / resid)
else:
ptol = presid * ptol_max_factor
old_ijob = ijob
ijob = 2
if iter_num > maxiter:
info = maxiter
break
if info >= 0 and not (resid <= atol):
# info isn't set appropriately otherwise
info = maxiter
return postprocess(x), info
def qmr(A, b, x0=None, tol=1e-5, maxiter=None, xtype=None, M1=None, M2=None, callback=None):
"""Use Quasi-Minimal Residual iteration to solve ``Ax = b``.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real-valued N-by-N matrix of the linear system.
It is required that the linear operator can produce
``Ax`` and ``A^T x``.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : integer
Provides convergence information:
0 : successful exit
>0 : convergence to tolerance not achieved, number of iterations
<0 : illegal input or breakdown
Other Parameters
----------------
x0 : {array, matrix}
Starting guess for the solution.
tol : float
Tolerance to achieve. The algorithm terminates when either the relative
or the absolute residual is below `tol`.
maxiter : integer
Maximum number of iterations. Iteration will stop after maxiter
steps even if the specified tolerance has not been achieved.
M1 : {sparse matrix, dense matrix, LinearOperator}
Left preconditioner for A.
M2 : {sparse matrix, dense matrix, LinearOperator}
Right preconditioner for A. Used together with the left
preconditioner M1. The matrix M1*A*M2 should have better
conditioned than A alone.
callback : function
User-supplied function to call after each iteration. It is called
as callback(xk), where xk is the current solution vector.
xtype : {'f','d','F','D'}
This parameter is DEPRECATED -- avoid using it.
The type of the result. If None, then it will be determined from
A.dtype.char and b. If A does not have a typecode method then it
will compute A.matvec(x0) to get a typecode. To save the extra
computation when A does not have a typecode attribute use xtype=0
for the same type as b or use xtype='f','d','F',or 'D'.
This parameter has been superseded by LinearOperator.
See Also
--------
LinearOperator
Examples
--------
>>> from scipy.sparse import csc_matrix
>>> from scipy.sparse.linalg import qmr
>>> A = csc_matrix([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = qmr(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
"""
A_ = A
A,M,x,b,postprocess = make_system(A,None,x0,b,xtype)
if M1 is None and M2 is None:
if hasattr(A_,'psolve'):
def left_psolve(b):
return A_.psolve(b,'left')
def right_psolve(b):
return A_.psolve(b,'right')
def left_rpsolve(b):
return A_.rpsolve(b,'left')
def right_rpsolve(b):
return A_.rpsolve(b,'right')
M1 = LinearOperator(A.shape, matvec=left_psolve, rmatvec=left_rpsolve)
M2 = LinearOperator(A.shape, matvec=right_psolve, rmatvec=right_rpsolve)
else:
def id(b):
return b
M1 = LinearOperator(A.shape, matvec=id, rmatvec=id)
M2 = LinearOperator(A.shape, matvec=id, rmatvec=id)
n = len(b)
if maxiter is None:
maxiter = n*10
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'qmrrevcom')
stoptest = getattr(_iterative, ltr + 'stoptest2')
resid = tol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(11*n,x.dtype)
ijob = 1
info = 0
ftflag = True
bnrm2 = -1.0
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*A.matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1*A.rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = M1.matvec(work[slice2])
elif (ijob == 4):
work[slice1] = M2.matvec(work[slice2])
elif (ijob == 5):
work[slice1] = M1.rmatvec(work[slice2])
elif (ijob == 6):
work[slice1] = M2.rmatvec(work[slice2])
elif (ijob == 7):
work[slice2] *= sclr2
work[slice2] += sclr1*A.matvec(x)
elif (ijob == 8):
if ftflag:
info = -1
ftflag = False
bnrm2, resid, info = stoptest(work[slice1], b, bnrm2, tol, info)
ijob = 2
if info > 0 and iter_ == maxiter and resid > tol:
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def gmres(A, b, x0=None, tol=1e-5, restart=None, maxiter=None, xtype=None, M=None, callback=None, restrt=None):
"""
Use Generalized Minimal RESidual iteration to solve ``Ax = b``.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real or complex N-by-N matrix of the linear system.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : int
Provides convergence information:
* 0 : successful exit
* >0 : convergence to tolerance not achieved, number of iterations
* <0 : illegal input or breakdown
Other parameters
----------------
x0 : {array, matrix}
Starting guess for the solution (a vector of zeros by default).
tol : float
Tolerance to achieve. The algorithm terminates when either the relative
or the absolute residual is below `tol`.
restart : int, optional
Number of iterations between restarts. Larger values increase
iteration cost, but may be necessary for convergence.
Default is 20.
maxiter : int, optional
Maximum number of iterations (restart cycles). Iteration will stop
after maxiter steps even if the specified tolerance has not been
achieved.
xtype : {'f','d','F','D'}
This parameter is DEPRECATED --- avoid using it.
The type of the result. If None, then it will be determined from
A.dtype.char and b. If A does not have a typecode method then it
will compute A.matvec(x0) to get a typecode. To save the extra
computation when A does not have a typecode attribute use xtype=0
for the same type as b or use xtype='f','d','F',or 'D'.
This parameter has been superseded by LinearOperator.
M : {sparse matrix, dense matrix, LinearOperator}
Inverse of the preconditioner of A. M should approximate the
inverse of A and be easy to solve for (see Notes). Effective
preconditioning dramatically improves the rate of convergence,
which implies that fewer iterations are needed to reach a given
error tolerance. By default, no preconditioner is used.
callback : function
User-supplied function to call after each iteration. It is called
as callback(rk), where rk is the current residual vector.
restrt : int, optional
DEPRECATED - use `restart` instead.
See Also
--------
LinearOperator
Notes
-----
A preconditioner, P, is chosen such that P is close to A but easy to solve
for. The preconditioner parameter required by this routine is
``M = P^-1``. The inverse should preferably not be calculated
explicitly. Rather, use the following template to produce M::
# Construct a linear operator that computes P^-1 * x.
import scipy.sparse.linalg as spla
M_x = lambda x: spla.spsolve(P, x)
M = spla.LinearOperator((n, n), M_x)
Examples
--------
>>> from scipy.sparse import csc_matrix
>>> from scipy.sparse.linalg import gmres
>>> A = csc_matrix([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = gmres(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
"""
# Change 'restrt' keyword to 'restart'
if restrt is None:
restrt = restart
elif restart is not None:
raise ValueError("Cannot specify both restart and restrt keywords. "
"Preferably use 'restart' only.")
A,M,x,b,postprocess = make_system(A,M,x0,b,xtype)
n = len(b)
if maxiter is None:
maxiter = n*10
if restrt is None:
restrt = 20
restrt = min(restrt, n)
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'gmresrevcom')
stoptest = getattr(_iterative, ltr + 'stoptest2')
resid = tol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros((6+restrt)*n,dtype=x.dtype)
work2 = _aligned_zeros((restrt+1)*(2*restrt+2),dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
bnrm2 = -1.0
iter_ = maxiter
old_ijob = ijob
first_pass = True
resid_ready = False
iter_num = 1
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, restrt, work, work2, iter_, resid, info, ndx1, ndx2, ijob)
# if callback is not None and iter_ > olditer:
# callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1): # gmres success, update last residual
if resid_ready and callback is not None:
callback(resid)
resid_ready = False
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(x)
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
if not first_pass and old_ijob == 3:
resid_ready = True
first_pass = False
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1*matvec(work[slice1])
if resid_ready and callback is not None:
callback(resid)
resid_ready = False
iter_num = iter_num+1
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
bnrm2, resid, info = stoptest(work[slice1], b, bnrm2, tol, info)
old_ijob = ijob
ijob = 2
if iter_num > maxiter:
break
if info >= 0 and resid > tol:
# info isn't set appropriately otherwise
info = maxiter
return postprocess(x), info
def bicg(A,
b,
x0=None,
tol=1e-5,
maxiter=None,
xtype=None,
M=None,
callback=None):
A, M, x, b, postprocess = make_system(A, M, x0, b, xtype)
n = len(b)
if maxiter is None:
maxiter = n * 10
matvec, rmatvec = A.matvec, A.rmatvec
psolve, rpsolve = M.matvec, M.rmatvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'bicgrevcom')
stoptest = getattr(_iterative, ltr + 'stoptest2')
resid = tol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(6 * n, dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
bnrm2 = -1.0
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1 * rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = psolve(work[slice2])
elif (ijob == 4):
work[slice1] = rpsolve(work[slice2])
elif (ijob == 5):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(x)
elif (ijob == 6):
if ftflag:
info = -1
ftflag = False
bnrm2, resid, info = stoptest(work[slice1], b, bnrm2, tol, info)
ijob = 2
if info > 0 and iter_ == maxiter and resid > tol:
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def presid_gmres(A,
b,
verbose,
x0=None,
tol=1e-05,
restart=None,
maxiter=None,
M=None):
callback = gmres_counter(verbose)
A, M, x, b, postprocess = make_system(A, M, x0, b)
n = len(b)
if maxiter is None:
maxiter = n * 10
if restart is None:
restart = 20
restart = min(restart, n)
matvec = A.matvec
psolve = M.matvec
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'gmresrevcom')
bnrm2 = np.linalg.norm(b)
Mb_nrm2 = np.linalg.norm(psolve(b))
get_residual = lambda: np.linalg.norm(matvec(x) - b)
atol = tol
if bnrm2 == 0:
return postprocess(b), 0
# Tolerance passed to GMRESREVCOM applies to the inner iteration
# and deals with the left-preconditioned residual.
ptol_max_factor = 1.0
ptol = Mb_nrm2 * min(ptol_max_factor, atol / bnrm2)
resid = np.nan
presid = np.nan
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros((6 + restart) * n, dtype=x.dtype)
work2 = _aligned_zeros((restart + 1) * (2 * restart + 2), dtype=x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
old_ijob = ijob
first_pass = True
resid_ready = False
iter_num = 1
while True:
### begin my modifications
if presid / bnrm2 < atol:
resid = presid / bnrm2
info = 1
if info: ptol = 10000
### end my modifications
x, iter_, presid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, restart, work, work2, iter_, presid, info, ndx1, ndx2, ijob, ptol)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1): # gmres success, update last residual
if resid_ready and callback is not None:
callback(presid / bnrm2)
resid_ready = False
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(x)
elif (ijob == 2):
work[slice1] = psolve(work[slice2])
if not first_pass and old_ijob == 3:
resid_ready = True
first_pass = False
elif (ijob == 3):
work[slice2] *= sclr2
work[slice2] += sclr1 * matvec(work[slice1])
if resid_ready and callback is not None:
callback(presid / bnrm2)
resid_ready = False
iter_num = iter_num + 1
elif (ijob == 4):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
# Inner loop tolerance control
if info or presid > ptol:
ptol_max_factor = min(1.0, 1.5 * ptol_max_factor)
else:
# Inner loop tolerance OK, but outer loop not.
ptol_max_factor = max(1e-16, 0.25 * ptol_max_factor)
if resid != 0:
ptol = presid * min(ptol_max_factor, atol / resid)
else:
ptol = presid * ptol_max_factor
old_ijob = ijob
ijob = 2
if iter_num > maxiter:
info = maxiter
break
if info >= 0 and not (resid <= atol):
# info isn't set appropriately otherwise
info = maxiter
return postprocess(x), info, mydict['resnorms']
def qmr(A,
b,
x0=None,
tol=1e-5,
maxiter=None,
M1=None,
M2=None,
callback=None,
atol=None):
"""Use Quasi-Minimal Residual iteration to solve ``Ax = b``.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real-valued N-by-N matrix of the linear system.
Alternatively, ``A`` can be a linear operator which can
produce ``Ax`` and ``A^T x`` using, e.g.,
``scipy.sparse.linalg.LinearOperator``.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : integer
Provides convergence information:
0 : successful exit
>0 : convergence to tolerance not achieved, number of iterations
<0 : illegal input or breakdown
Other Parameters
----------------
x0 : {array, matrix}
Starting guess for the solution.
tol, atol : float, optional
Tolerances for convergence, ``norm(residual) <= max(tol*norm(b), atol)``.
The default for ``atol`` is ``'legacy'``, which emulates
a different legacy behavior.
.. warning::
The default value for `atol` will be changed in a future release.
For future compatibility, specify `atol` explicitly.
maxiter : integer
Maximum number of iterations. Iteration will stop after maxiter
steps even if the specified tolerance has not been achieved.
M1 : {sparse matrix, dense matrix, LinearOperator}
Left preconditioner for A.
M2 : {sparse matrix, dense matrix, LinearOperator}
Right preconditioner for A. Used together with the left
preconditioner M1. The matrix M1*A*M2 should have better
conditioned than A alone.
callback : function
User-supplied function to call after each iteration. It is called
as callback(xk), where xk is the current solution vector.
See Also
--------
LinearOperator
Examples
--------
>>> from scipy.sparse import csc_matrix
>>> from scipy.sparse.linalg import qmr
>>> A = csc_matrix([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = qmr(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
"""
A_ = A
A, M, x, b, postprocess = make_system(A, None, x0, b)
if M1 is None and M2 is None:
if hasattr(A_, 'psolve'):
def left_psolve(b):
return A_.psolve(b, 'left')
def right_psolve(b):
return A_.psolve(b, 'right')
def left_rpsolve(b):
return A_.rpsolve(b, 'left')
def right_rpsolve(b):
return A_.rpsolve(b, 'right')
M1 = LinearOperator(A.shape,
matvec=left_psolve,
rmatvec=left_rpsolve)
M2 = LinearOperator(A.shape,
matvec=right_psolve,
rmatvec=right_rpsolve)
else:
def id(b):
return b
M1 = LinearOperator(A.shape, matvec=id, rmatvec=id)
M2 = LinearOperator(A.shape, matvec=id, rmatvec=id)
n = len(b)
if maxiter is None:
maxiter = n * 10
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'qmrrevcom')
get_residual = lambda: np.linalg.norm(A.matvec(x) - b)
atol = _get_atol(tol, atol, np.linalg.norm(b), get_residual, 'qmr')
if atol == 'exit':
return postprocess(x), 0
resid = atol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(11 * n, x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1 * A.matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1 * A.rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = M1.matvec(work[slice2])
elif (ijob == 4):
work[slice1] = M2.matvec(work[slice2])
elif (ijob == 5):
work[slice1] = M1.rmatvec(work[slice2])
elif (ijob == 6):
work[slice1] = M2.rmatvec(work[slice2])
elif (ijob == 7):
work[slice2] *= sclr2
work[slice2] += sclr1 * A.matvec(x)
elif (ijob == 8):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
ijob = 2
if info > 0 and iter_ == maxiter and not (resid <= atol):
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def qmr(A, b, x0=None, tol=1e-5, maxiter=None, M1=None, M2=None, callback=None,
atol=None):
"""Use Quasi-Minimal Residual iteration to solve ``Ax = b``.
Parameters
----------
A : {sparse matrix, dense matrix, LinearOperator}
The real-valued N-by-N matrix of the linear system.
It is required that the linear operator can produce
``Ax`` and ``A^T x``.
b : {array, matrix}
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : {array, matrix}
The converged solution.
info : integer
Provides convergence information:
0 : successful exit
>0 : convergence to tolerance not achieved, number of iterations
<0 : illegal input or breakdown
Other Parameters
----------------
x0 : {array, matrix}
Starting guess for the solution.
tol, atol : float, optional
Tolerances for convergence, ``norm(residual) <= max(tol*norm(b), atol)``.
The default for ``atol`` is ``'legacy'``, which emulates
a different legacy behavior.
.. warning::
The default value for `atol` will be changed in a future release.
For future compatibility, specify `atol` explicitly.
maxiter : integer
Maximum number of iterations. Iteration will stop after maxiter
steps even if the specified tolerance has not been achieved.
M1 : {sparse matrix, dense matrix, LinearOperator}
Left preconditioner for A.
M2 : {sparse matrix, dense matrix, LinearOperator}
Right preconditioner for A. Used together with the left
preconditioner M1. The matrix M1*A*M2 should have better
conditioned than A alone.
callback : function
User-supplied function to call after each iteration. It is called
as callback(xk), where xk is the current solution vector.
See Also
--------
LinearOperator
Examples
--------
>>> from scipy.sparse import csc_matrix
>>> from scipy.sparse.linalg import qmr
>>> A = csc_matrix([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = qmr(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
"""
A_ = A
A, M, x, b, postprocess = make_system(A, None, x0, b)
if M1 is None and M2 is None:
if hasattr(A_,'psolve'):
def left_psolve(b):
return A_.psolve(b,'left')
def right_psolve(b):
return A_.psolve(b,'right')
def left_rpsolve(b):
return A_.rpsolve(b,'left')
def right_rpsolve(b):
return A_.rpsolve(b,'right')
M1 = LinearOperator(A.shape, matvec=left_psolve, rmatvec=left_rpsolve)
M2 = LinearOperator(A.shape, matvec=right_psolve, rmatvec=right_rpsolve)
else:
def id(b):
return b
M1 = LinearOperator(A.shape, matvec=id, rmatvec=id)
M2 = LinearOperator(A.shape, matvec=id, rmatvec=id)
n = len(b)
if maxiter is None:
maxiter = n*10
ltr = _type_conv[x.dtype.char]
revcom = getattr(_iterative, ltr + 'qmrrevcom')
get_residual = lambda: np.linalg.norm(A.matvec(x) - b)
atol = _get_atol(tol, atol, np.linalg.norm(b), get_residual, 'qmr')
if atol == 'exit':
return postprocess(x), 0
resid = atol
ndx1 = 1
ndx2 = -1
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work = _aligned_zeros(11*n,x.dtype)
ijob = 1
info = 0
ftflag = True
iter_ = maxiter
while True:
olditer = iter_
x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
if callback is not None and iter_ > olditer:
callback(x)
slice1 = slice(ndx1-1, ndx1-1+n)
slice2 = slice(ndx2-1, ndx2-1+n)
if (ijob == -1):
if callback is not None:
callback(x)
break
elif (ijob == 1):
work[slice2] *= sclr2
work[slice2] += sclr1*A.matvec(work[slice1])
elif (ijob == 2):
work[slice2] *= sclr2
work[slice2] += sclr1*A.rmatvec(work[slice1])
elif (ijob == 3):
work[slice1] = M1.matvec(work[slice2])
elif (ijob == 4):
work[slice1] = M2.matvec(work[slice2])
elif (ijob == 5):
work[slice1] = M1.rmatvec(work[slice2])
elif (ijob == 6):
work[slice1] = M2.rmatvec(work[slice2])
elif (ijob == 7):
work[slice2] *= sclr2
work[slice2] += sclr1*A.matvec(x)
elif (ijob == 8):
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
ijob = 2
if info > 0 and iter_ == maxiter and not (resid <= atol):
# info isn't set appropriately otherwise
info = iter_
return postprocess(x), info
def presid_gmres(A,
M,
b,
verbose,
x0=None,
tol=1e-05,
restart=None,
maxiter=None):
matvec = A
psolve = M
comm = A.comm
rank = A.rank
n = A.n
dtype = A.dtype
isMaster = rank == 0
callback = gmres_counter(verbose) if isMaster else None
x = np.zeros(n, dtype=dtype) if x0 is None else x0
if maxiter is None: maxiter = n * 10
if restart is None: restart = 20
restart = min(restart, n)
ltr = _type_conv[np.dtype(dtype).char]
revcom = getattr(_iterative, ltr + 'gmresrevcom')
pb = psolve(b)
mb = matvec(b)
if rank == 0:
bnrm2 = np.linalg.norm(b)
Mb_nrm2 = np.linalg.norm(pb)
get_residual = lambda: np.linalg.norm(mb - b)
atol = tol
else:
bnrm2 = None
bnrm2 = comm.bcast(bnrm2, root=0)
if bnrm2 == 0:
return postprocess(b), 0
if rank == 0:
# Tolerance passed to GMRESREVCOM applies to the inner iteration
# and deals with the left-preconditioned residual.
ptol_max_factor = 1.0
ptol = Mb_nrm2 * min(ptol_max_factor, atol / bnrm2)
resid = np.nan
presid = np.nan
# Use _aligned_zeros to work around a f2py bug in Numpy 1.9.1
work2 = _aligned_zeros((restart + 1) * (2 * restart + 2), dtype=dtype)
info = 0
ftflag = True
iter_ = maxiter
first_pass = True
resid_ready = False
ndx1 = 1
ndx2 = -1
ijob = 1
old_ijob = ijob
work = _aligned_zeros((6 + restart) * n, dtype=dtype)
iter_num = 1
while True:
if rank == 0:
### begin my modifications
if presid / bnrm2 < atol:
resid = presid / bnrm2
info = 1
if info: ptol = 10000
### end my modifications
x, iter_, presid, info, ndx1, ndx2, sclr1, sclr2, ijob = \
revcom(b, x, restart, work, work2, iter_, presid, info, ndx1, ndx2, ijob, ptol)
ijob = comm.bcast(ijob, root=0)
ndx1 = comm.bcast(ndx1, root=0)
ndx2 = comm.bcast(ndx2, root=0)
slice1 = slice(ndx1 - 1, ndx1 - 1 + n)
slice2 = slice(ndx2 - 1, ndx2 - 1 + n)
if (ijob == -1): # gmres success, update last residual
if rank == 0:
if resid_ready and callback is not None:
callback(presid / bnrm2)
resid_ready = False
break
elif (ijob == 1):
upd = matvec(x)
if rank == 0:
work[slice2] *= sclr2
work[slice2] += sclr1 * upd
elif (ijob == 2):
upd = psolve(work[slice2])
if rank == 0:
work[slice1] = upd
if not first_pass and old_ijob == 3:
resid_ready = True
first_pass = False
elif (ijob == 3):
upd = matvec(work[slice1])
if rank == 0:
work[slice2] *= sclr2
work[slice2] += sclr1 * upd
if resid_ready and callback is not None:
callback(presid / bnrm2)
resid_ready = False
iter_num = iter_num + 1
elif (ijob == 4):
if rank == 0:
if ftflag:
info = -1
ftflag = False
resid, info = _stoptest(work[slice1], atol)
# Inner loop tolerance control
if info or presid > ptol:
ptol_max_factor = min(1.0, 1.5 * ptol_max_factor)
else:
# Inner loop tolerance OK, but outer loop not.
ptol_max_factor = max(1e-16, 0.25 * ptol_max_factor)
if resid != 0:
ptol = presid * min(ptol_max_factor, atol / resid)
else:
ptol = presid * ptol_max_factor
if rank == 0:
old_ijob = ijob
ijob = 2
# need to set ijob according to the master rank
ijob = comm.bcast(ijob, root=0)
iter_num = comm.bcast(iter_num, root=0)
if iter_num > maxiter:
info = maxiter
break
if rank == 0:
if info >= 0 and not (resid <= atol):
# info isn't set appropriately otherwise
info = maxiter
return x, info, mydict['resnorms']
else:
return None
