def f(x, y, z):
# Solve for x[:n]:
#
# A*x[:n] = bx[:n] + P' * ( ((D1-D2)*(D1+D2)^{-1})*bx[n:]
# + (2*D1*D2*(D1+D2)^{-1}) * (bz[:m] - bz[m:]) ).
blas.copy((mul(div(d1 - d2, d1 + d2), x[n:]) +
mul(2 * D, z[:m] - z[m:])), u)
blas.gemv(P, u, x, beta=1.0, trans='T')
lapack.potrs(A, x)
# x[n:] := (D1+D2)^{-1} * (bx[n:] - D1*bz[:m] - D2*bz[m:]
# + (D1-D2)*P*x[:n])
base.gemv(P, x, u)
x[n:] = div(
x[n:] - mul(d1, z[:m]) - mul(d2, z[m:]) + mul(d1 - d2, u),
d1 + d2)
# z[:m] := d1[:m] .* ( P*x[:n] - x[n:] - bz[:m])
# z[m:] := d2[m:] .* (-P*x[:n] - x[n:] - bz[m:])
z[:m] = mul(di[:m], u - x[n:] - z[:m])
z[m:] = mul(di[m:], -u - x[n:] - z[m:])
def Fgp(x = None, z = None):
if x is None: return mnl, matrix(0.0, (n,1))
f = matrix(0.0, (mnl+1,1))
Df = matrix(0.0, (mnl+1,n))
# y = F*x+g
blas.copy(g, y)
base.gemv(F, x, y, beta=1.0)
if z is not None: H = matrix(0.0, (n,n))
for i, start, stop in ind:
# yi := exp(yi) = exp(Fi*x+gi)
ymax = max(y[start:stop])
y[start:stop] = base.exp(y[start:stop] - ymax)
# fi = log sum yi = log sum exp(Fi*x+gi)
ysum = blas.asum(y, n=stop-start, offset=start)
f[i] = ymax + math.log(ysum)
# yi := yi / sum(yi) = exp(Fi*x+gi) / sum(exp(Fi*x+gi))
blas.scal(1.0/ysum, y, n=stop-start, offset=start)
# gradfi := Fi' * yi
# = Fi' * exp(Fi*x+gi) / sum(exp(Fi*x+gi))
base.gemv(F, y, Df, trans='T', m=stop-start, incy=mnl+1,
offsetA=start, offsetx=start, offsety=i)
if z is not None:
# Hi = Fi' * (diag(yi) - yi*yi') * Fi
# = Fisc' * Fisc
# where
# Fisc = diag(yi)^1/2 * (I - 1*yi') * Fi
# = diag(yi)^1/2 * (Fi - 1*gradfi')
Fsc[:K[i], :] = F[start:stop, :]
for k in range(start,stop):
blas.axpy(Df, Fsc, n=n, alpha=-1.0, incx=mnl+1,
incy=Fsc.size[0], offsetx=i, offsety=k-start)
blas.scal(math.sqrt(y[k]), Fsc, inc=Fsc.size[0],
offset=k-start)
# H += z[i]*Hi = z[i] * Fisc' * Fisc
blas.syrk(Fsc, H, trans='T', k=stop-start, alpha=z[i],
beta=1.0)
if z is None:
return f, Df
return f, Df, H
def proj(y, ip=True):
if not ip: y = +y
tmp = matrix(0.0, size=(meq, 1))
ypre = +y
base.gemv(L,y,tmp,trans='T',\
m = nssq, n = meq, beta = 1)
cholmod.solve(LTLi, tmp)
base.gemv(L,tmp,y,beta=1.0,alpha=-1.0,trans='N',\
m = nssq, n = meq)
if not ip: return y
def _gen_randsdp(self,V,m,d,seed):
"""
Random data generator
"""
setseed(seed)
n = self._n
V = chompack.tril(V)
N = len(V)
I = V.I; J = V.J
Il = misc.sub2ind((n,n),I,J)
Id = matrix([i for i in range(len(Il)) if I[i]==J[i]])
# generate random y with norm 1
y0 = normal(m,1)
y0 /= blas.nrm2(y0)
# generate random S0, X0
S0 = mk_rand(V,cone='posdef',seed=seed)
X0 = mk_rand(V,cone='completable',seed=seed)
# generate random A1,...,Am
if type(d) is float:
nz = min(max(1, int(round(d*N))), N)
A = sparse([[spmatrix(normal(N,1),Il,[0 for i in range(N)],(n**2,1))],
[spmatrix(normal(nz*m,1),
[i for j in range(m) for i in random.sample(Il,nz)],
[j for j in range(m) for i in range(nz)],(n**2,m))]])
elif type(d) is list:
if len(d) == m:
nz = [min(max(1, int(round(v*N))), N) for v in d]
nnz = sum(nz)
A = sparse([[spmatrix(normal(N,1),Il,[0 for i in range(N)],(n**2,1))],
[spmatrix(normal(nnz,1),
[i for j in range(m) for i in random.sample(Il,nz[j])],
[j for j in range(m) for i in range(nz[j])],(n**2,m))]])
else: raise TypeError
# compute A0
u = +S0.V
for k in range(m):
base.gemv(A[:,k+1][Il],matrix(y0[k]),u,beta=1.0,trans='N')
A[Il,0] = u
self._A = A
# compute b
X0[Il[Id]] *= 0.5
self._b = matrix(0.,(m,1))
u = matrix(0.)
for k in range(m):
base.gemv(A[:,k+1][Il],X0.V,u,trans='T',alpha=2.0)
self._b[k] = u
def Gf(u, v, alpha=1.0, beta=0.0, trans='N'):
if trans == 'N':
# v[:m] := alpha * G * u[0] + beta * v[:m]
base.gemv(G, u[0], v, alpha=alpha, beta=beta)
# v[m:] := alpha * [-u[1], -A(u[0])'; -A(u[0]), -u[2]]
# + beta * v[m:]
blas.scal(beta, v, offset=m)
v[m + I11] -= alpha * u[1][:]
v[m + I21] -= alpha * A * u[0]
v[m + I22] -= alpha * u[2][:]
else:
# v[0] := alpha * ( G.T * u[:m] - 2.0 * A.T * u[m + I21] )
# + beta v[1]
base.gemv(G, u, v[0], trans='T', alpha=alpha, beta=beta)
base.gemv(A,
u[m + I21],
v[0],
trans='T',
alpha=-2.0 * alpha,
beta=1.0)
# v[1] := -alpha * u[m + I11] + beta * v[1]
blas.scal(beta, v[1])
blas.axpy(u[m + I11], v[1], alpha=-alpha)
# v[2] := -alpha * u[m + I22] + beta * v[2]
blas.scal(beta, v[2])
blas.axpy(u[m + I22], v[2], alpha=-alpha)
def Gf(u, v, alpha = 1.0, beta = 0.0, trans = 'N'):
if trans == 'N':
# v[:m] := alpha * G * u[0] + beta * v[:m]
base.gemv(G, u[0], v, alpha = alpha, beta = beta)
# v[m:] := alpha * [-u[1], -A(u[0])'; -A(u[0]), -u[2]]
# + beta * v[m:]
blas.scal(beta, v, offset = m)
v[m + I11] -= alpha * u[1][:]
v[m + I21] -= alpha * A * u[0]
v[m + I22] -= alpha * u[2][:]
else:
# v[0] := alpha * ( G.T * u[:m] - 2.0 * A.T * u[m + I21] )
# + beta v[1]
base.gemv(G, u, v[0], trans = 'T', alpha = alpha, beta = beta)
base.gemv(A, u[m + I21], v[0], trans = 'T', alpha = -2.0*alpha,
beta = 1.0)
# v[1] := -alpha * u[m + I11] + beta * v[1]
blas.scal(beta, v[1])
blas.axpy(u[m + I11], v[1], alpha = -alpha)
# v[2] := -alpha * u[m + I22] + beta * v[2]
blas.scal(beta, v[2])
blas.axpy(u[m + I22], v[2], alpha = -alpha)
def G(x, y, alpha=1.0, beta=0.0, trans='N'):
"""
Implements the linear operator
[ -DX E -d -I ]
[ 0 0 0 -I ]
[ 0 -e_1' 0 0 ]
G = [ -P_1' 0 0 0 ]
[ . . . . ]
[ 0 -e_k' 0 0 ]
[ -P_k' 0 0 0 ]
and its adjoint G'.
"""
if trans == 'N':
tmp = +y[:m]
# y[:m] = alpha*(-DXw + Et - d*b - v) + beta*y[:m]
base.gemv(E, x[n:n + k], tmp, alpha=alpha, beta=beta)
blas.axpy(x[n + k + 1:], tmp, alpha=-alpha)
blas.axpy(d, tmp, alpha=-alpha * x[n + k])
y[:m] = tmp
base.gemv(X, x[:n], tmp, alpha=alpha, beta=0.0)
tmp = mul(d, tmp)
y[:m] -= tmp
# y[m:2*m] = -v
y[m:2 * m] = -alpha * x[n + k + 1:] + beta * y[m:2 * m]
# SOC 1,...,k
for i in range(k):
l = 2 * m + i * (n + 1)
y[l] = -alpha * x[n + i] + beta * y[l]
y[l + 1:l + 1 +
n] = -alpha * P[i] * x[:n] + beta * y[l + 1:l + 1 + n]
else:
tmp1 = mul(d, x[:m])
tmp2 = y[:n]
blas.gemv(X, tmp1, tmp2, trans='T', alpha=-alpha, beta=beta)
for i in range(k):
l = 2 * m + 1 + i * (n + 1)
blas.gemv(P[i],
x[l:l + n],
tmp2,
trans='T',
alpha=-alpha,
beta=1.0)
y[:n] = tmp2
tmp2 = y[n:n + k]
base.gemv(E, x[:m], tmp2, trans='T', alpha=alpha, beta=beta)
blas.axpy(x[2 * m:2 * m + k * (1 + n):n + 1], tmp2, alpha=-alpha)
y[n:n + k] = tmp2
y[n + k] = -alpha * blas.dot(d, x[:m]) + beta * y[n + k]
y[n + k +
1:] = -alpha * (x[:m] + x[m:2 * m]) + beta * y[n + k + 1:]
def checksol(sol, A, B, C = None, d = None, G = None, h = None):
"""
Check optimality conditions
C * x + G' * z + A'(Z) + d = 0
G * x <= h
z >= 0, || Z || < = 1
z' * (h - G*x) = 0
tr (Z' * (A(x) + B)) = || A(x) + B ||_*.
"""
p, q = B.size
n = A.size[1]
if G is None: G = spmatrix([], [], [], (0, n))
if h is None: h = matrix(0.0, (0, 1))
m = h.size[0]
if C is None: C = spmatrix(0.0, [], [], (n,n))
if d is None: d = matrix(0.0, (n, 1))
if sol['status'] is 'optimal':
res = +d
base.symv(C, sol['x'], res, beta = 1.0)
base.gemv(G, sol['z'], res, beta = 1.0, trans = 'T')
base.gemv(A, sol['Z'], res, beta = 1.0, trans = 'T')
print "Dual residual: %e" %blas.nrm2(res)
if m:
print "Minimum primal slack (scalar inequalities): %e" \
%min(h - G*sol['x'])
print "Minimum dual slack (scalar inequalities): %e" \
%min(sol['z'])
if p:
s = matrix(0.0, (p,1))
X = matrix(A*sol['x'], (p, q)) + B
lapack.gesvd(+X, s)
nrmX = sum(s)
lapack.gesvd(+sol['Z'], s)
nrmZ = max(s)
print "Norm of Z: %e" %nrmZ
print "Nuclear norm of A(x) + B: %e" %nrmX
print "Inner product of Z and A(x) + B: %e" \
%blas.dot(sol['Z'], X)
elif sol['status'] is 'primal infeasible':
res = matrix(0.0, (n,1))
base.gemv(G, sol['z'], res, beta = 1.0, trans = 'T')
print "Dual residual: %e" %blas.nrm2(res)
print "h' * z = %e" %blas.dot(h, sol['z'])
print "Minimum dual slack (scalar inequalities): %e" \
%min(sol['z'])
else:
pass
def checksol(sol, A, B, C=None, d=None, G=None, h=None):
"""
Check optimality conditions
C * x + G' * z + A'(Z) + d = 0
G * x <= h
z >= 0, || Z || < = 1
z' * (h - G*x) = 0
tr (Z' * (A(x) + B)) = || A(x) + B ||_*.
"""
p, q = B.size
n = A.size[1]
if G is None: G = spmatrix([], [], [], (0, n))
if h is None: h = matrix(0.0, (0, 1))
m = h.size[0]
if C is None: C = spmatrix(0.0, [], [], (n, n))
if d is None: d = matrix(0.0, (n, 1))
if sol['status'] is 'optimal':
res = +d
base.symv(C, sol['x'], res, beta=1.0)
base.gemv(G, sol['z'], res, beta=1.0, trans='T')
base.gemv(A, sol['Z'], res, beta=1.0, trans='T')
print "Dual residual: %e" % blas.nrm2(res)
if m:
print "Minimum primal slack (scalar inequalities): %e" \
%min(h - G*sol['x'])
print "Minimum dual slack (scalar inequalities): %e" \
%min(sol['z'])
if p:
s = matrix(0.0, (p, 1))
X = matrix(A * sol['x'], (p, q)) + B
lapack.gesvd(+X, s)
nrmX = sum(s)
lapack.gesvd(+sol['Z'], s)
nrmZ = max(s)
print "Norm of Z: %e" % nrmZ
print "Nuclear norm of A(x) + B: %e" % nrmX
print "Inner product of Z and A(x) + B: %e" \
%blas.dot(sol['Z'], X)
elif sol['status'] is 'primal infeasible':
res = matrix(0.0, (n, 1))
base.gemv(G, sol['z'], res, beta=1.0, trans='T')
print "Dual residual: %e" % blas.nrm2(res)
print "h' * z = %e" % blas.dot(h, sol['z'])
print "Minimum dual slack (scalar inequalities): %e" \
%min(sol['z'])
else:
pass
def f(x, y, z):
# Solve for x[:n]:
#
# A*x[:n] = bx[:n] + P' * ( ((D1-D2)*(D1+D2)^{-1})*bx[n:]
# + (2*D1*D2*(D1+D2)^{-1}) * (bz[:m] - bz[m:]) ).
blas.copy(( mul( div(d1-d2, d1+d2), x[n:]) +
mul( 2*D, z[:m]-z[m:] ) ), u)
blas.gemv(P, u, x, beta = 1.0, trans = 'T')
lapack.potrs(A, x)
# x[n:] := (D1+D2)^{-1} * (bx[n:] - D1*bz[:m] - D2*bz[m:]
# + (D1-D2)*P*x[:n])
base.gemv(P, x, u)
x[n:] = div( x[n:] - mul(d1, z[:m]) - mul(d2, z[m:]) +
mul(d1-d2, u), d1+d2 )
# z[:m] := d1[:m] .* ( P*x[:n] - x[n:] - bz[:m])
# z[m:] := d2[m:] .* (-P*x[:n] - x[n:] - bz[m:])
z[:m] = mul(di[:m], u-x[n:]-z[:m])
z[m:] = mul(di[m:], -u-x[n:]-z[m:])
def G(x, y, alpha = 1.0, beta = 0.0, trans = 'N'):
"""
Implements the linear operator
[ -DX E -d -I ]
[ 0 0 0 -I ]
[ 0 -e_1' 0 0 ]
G = [ -P_1' 0 0 0 ]
[ . . . . ]
[ 0 -e_k' 0 0 ]
[ -P_k' 0 0 0 ]
and its adjoint G'.
"""
if trans == 'N':
tmp = +y[:m]
# y[:m] = alpha*(-DXw + Et - d*b - v) + beta*y[:m]
base.gemv(E, x[n:n+k], tmp, alpha = alpha, beta = beta)
blas.axpy(x[n+k+1:], tmp, alpha = -alpha)
blas.axpy(d, tmp, alpha = -alpha*x[n+k])
y[:m] = tmp
base.gemv(X, x[:n], tmp, alpha = alpha, beta = 0.0)
tmp = mul(d,tmp)
y[:m] -= tmp
# y[m:2*m] = -v
y[m:2*m] = -alpha * x[n+k+1:] + beta * y[m:2*m]
# SOC 1,...,k
for i in range(k):
l = 2*m+i*(n+1)
y[l] = -alpha * x[n+i] + beta * y[l]
y[l+1:l+1+n] = -alpha * P[i] * x[:n] + beta * y[l+1:l+1+n];
else:
tmp1 = mul(d,x[:m])
tmp2 = y[:n]
blas.gemv(X, tmp1, tmp2, trans = 'T', alpha = -alpha, beta = beta)
for i in range(k):
l = 2*m+1+i*(n+1)
blas.gemv(P[i], x[l:l+n], tmp2, trans = 'T', alpha = -alpha, beta = 1.0)
y[:n] = tmp2
tmp2 = y[n:n+k]
base.gemv(E, x[:m], tmp2, trans = 'T', alpha = alpha, beta = beta)
blas.axpy(x[2*m:2*m+k*(1+n):n+1], tmp2, alpha = -alpha)
y[n:n+k] = tmp2
y[n+k] = -alpha * blas.dot(d,x[:m]) + beta * y[n+k]
y[n+k+1:] = -alpha * (x[:m] + x[m:2*m]) + beta * y[n+k+1:]
def f(x, y, z):
"""
Solve
C * ux + G' * uzl - 2*A'(uzs21) = bx
-uzs11 = bX1
-uzs22 = bX2
G * ux - D^2 * uzl = bzl
[ -uX1 -A(ux)' ] [ uzs11 uzs21' ]
[ ] - T * [ ] * T = bzs.
[ -A(ux) -uX2 ] [ uzs21 uzs22 ]
On entry, x = (bx, bX1, bX2) and z = [ bzl; bzs[:] ].
On exit, x = (ux, uX1, uX2) and z = [ D*uzl; (r'*uzs*r)[:] ].
Define X = uzs21, Z = T * uzs * T:
C * ux + G' * uzl - 2*A'(X) = bx
[ 0 X' ] [ bX1 0 ]
T * [ ] * T - Z = T * [ ] * T
[ X 0 ] [ 0 bX2 ]
G * ux - D^2 * uzl = bzl
[ -uX1 -A(ux)' ] [ Z11 Z21' ]
[ ] - [ ] = bzs
[ -A(ux) -uX2 ] [ Z21 Z22 ]
Return x = (ux, uX1, uX2), z = [ D*uzl; (rti'*Z*rti)[:] ].
We use the congruence transformation
[ V1 0 ] [ T11 T21' ] [ V1' 0 ] [ I S' ]
[ ] [ ] [ ] = [ ]
[ 0 V2' ] [ T21 T22 ] [ 0 V2 ] [ S I ]
and the factorization
X + S * X' * S = L( L'(X) )
to write this as
C * ux + G' * uzl - 2*A'(X) = bx
L'(V2^-1 * X * V1^-1) - L^-1(V2' * Z21 * V1') = bX
G * ux - D^2 * uzl = bzl
[ -uX1 -A(ux)' ] [ Z11 Z21' ]
[ ] - [ ] = bzs,
[ -A(ux) -uX2 ] [ Z21 Z22 ]
or
C * ux + Gs' * uuzl - 2*As'(XX) = bx
XX - ZZ21 = bX
Gs * ux - uuzl = D^-1 * bzl
-As(ux) - ZZ21 = bbzs_21
-uX1 - Z11 = bzs_11
-uX2 - Z22 = bzs_22
if we introduce scaled variables
uuzl = D * uzl
XX = L'(V2^-1 * X * V1^-1)
= L'(V2^-1 * uzs21 * V1^-1)
ZZ21 = L^-1(V2' * Z21 * V1')
and define
bbzs_21 = L^-1(V2' * bzs_21 * V1')
[ bX1 0 ]
bX = L^-1( V2' * (T * [ ] * T)_21 * V1').
[ 0 bX2 ]
Eliminating Z21 gives
C * ux + Gs' * uuzl - 2*As'(XX) = bx
Gs * ux - uuzl = D^-1 * bzl
-As(ux) - XX = bbzs_21 - bX
-uX1 - Z11 = bzs_11
-uX2 - Z22 = bzs_22
and eliminating uuzl and XX gives
H * ux = bx + Gs' * D^-1 * bzl + 2*As'(bX - bbzs_21)
Gs * ux - uuzl = D^-1 * bzl
-As(ux) - XX = bbzs_21 - bX
-uX1 - Z11 = bzs_11
-uX2 - Z22 = bzs_22.
In summary, we can use the following algorithm:
1. bXX := bX - bbzs21
[ bX1 0 ]
= L^-1( V2' * ((T * [ ] * T)_21 - bzs_21) * V1')
[ 0 bX2 ]
2. Solve H * ux = bx + Gs' * D^-1 * bzl + 2*As'(bXX).
3. From ux, compute
uuzl = Gs*ux - D^-1 * bzl and
X = V2 * L^-T(-As(ux) + bXX) * V1.
4. Return ux, uuzl,
rti' * Z * rti = r' * [ -bX1, X'; X, -bX2 ] * r
and uX1 = -Z11 - bzs_11, uX2 = -Z22 - bzs_22.
"""
# Save bzs_11, bzs_22, bzs_21.
lapack.lacpy(z, bz11, uplo = 'L', m = q, n = q, ldA = p+q,
offsetA = m)
lapack.lacpy(z, bz21, m = p, n = q, ldA = p+q, offsetA = m+q)
lapack.lacpy(z, bz22, uplo = 'L', m = p, n = p, ldA = p+q,
offsetA = m + (p+q+1)*q)
# zl := D^-1 * zl
# = D^-1 * bzl
blas.tbmv(W['di'], z, n = m, k = 0, ldA = 1)
# zs := r' * [ bX1, 0; 0, bX2 ] * r.
# zs := [ bX1, 0; 0, bX2 ]
blas.scal(0.0, z, offset = m)
lapack.lacpy(x[1], z, uplo = 'L', m = q, n = q, ldB = p+q,
offsetB = m)
lapack.lacpy(x[2], z, uplo = 'L', m = p, n = p, ldB = p+q,
offsetB = m + (p+q+1)*q)
# scale diagonal of zs by 1/2
blas.scal(0.5, z, inc = p+q+1, offset = m)
# a := tril(zs)*r
blas.copy(r, a)
blas.trmm(z, a, side = 'L', m = p+q, n = p+q, ldA = p+q, ldB =
p+q, offsetA = m)
# zs := a'*r + r'*a
blas.syr2k(r, a, z, trans = 'T', n = p+q, k = p+q, ldB = p+q,
ldC = p+q, offsetC = m)
# bz21 := L^-1( V2' * ((r * zs * r')_21 - bz21) * V1')
#
# [ bX1 0 ]
# = L^-1( V2' * ((T * [ ] * T)_21 - bz21) * V1').
# [ 0 bX2 ]
# a = [ r21 r22 ] * z
# = [ r21 r22 ] * r' * [ bX1, 0; 0, bX2 ] * r
# = [ T21 T22 ] * [ bX1, 0; 0, bX2 ] * r
blas.symm(z, r, a, side = 'R', m = p, n = p+q, ldA = p+q,
ldC = p+q, offsetB = q)
# bz21 := -bz21 + a * [ r11, r12 ]'
# = -bz21 + (T * [ bX1, 0; 0, bX2 ] * T)_21
blas.gemm(a, r, bz21, transB = 'T', m = p, n = q, k = p+q,
beta = -1.0, ldA = p+q, ldC = p)
# bz21 := V2' * bz21 * V1'
# = V2' * (-bz21 + (T*[bX1, 0; 0, bX2]*T)_21) * V1'
blas.gemm(V2, bz21, tmp, transA = 'T', m = p, n = q, k = p,
ldB = p)
blas.gemm(tmp, V1, bz21, transB = 'T', m = p, n = q, k = q,
ldC = p)
# bz21[:] := D * (I-P) * bz21[:]
# = L^-1 * bz21[:]
# = bXX[:]
blas.copy(bz21, tmp)
base.gemv(P, bz21, tmp, alpha = -1.0, beta = 1.0)
base.gemv(D, tmp, bz21)
# Solve H * ux = bx + Gs' * D^-1 * bzl + 2*As'(bXX).
# x[0] := x[0] + Gs'*zl + 2*As'(bz21)
# = bx + G' * D^-1 * bzl + 2 * As'(bXX)
blas.gemv(Gs, z, x[0], trans = 'T', alpha = 1.0, beta = 1.0)
blas.gemv(As, bz21, x[0], trans = 'T', alpha = 2.0, beta = 1.0)
# x[0] := H \ x[0]
# = ux
lapack.potrs(H, x[0])
# uuzl = Gs*ux - D^-1 * bzl
blas.gemv(Gs, x[0], z, alpha = 1.0, beta = -1.0)
# bz21 := V2 * L^-T(-As(ux) + bz21) * V1
# = X
blas.gemv(As, x[0], bz21, alpha = -1.0, beta = 1.0)
blas.tbsv(DV, bz21, n = p*q, k = 0, ldA = 1)
blas.copy(bz21, tmp)
base.gemv(P, tmp, bz21, alpha = -1.0, beta = 1.0, trans = 'T')
blas.gemm(V2, bz21, tmp)
blas.gemm(tmp, V1, bz21)
# zs := -zs + r' * [ 0, X'; X, 0 ] * r
# = r' * [ -bX1, X'; X, -bX2 ] * r.
# a := bz21 * [ r11, r12 ]
# = X * [ r11, r12 ]
blas.gemm(bz21, r, a, m = p, n = p+q, k = q, ldA = p, ldC = p+q)
# z := -z + [ r21, r22 ]' * a + a' * [ r21, r22 ]
# = rti' * uzs * rti
blas.syr2k(r, a, z, trans = 'T', beta = -1.0, n = p+q, k = p,
offsetA = q, offsetC = m, ldB = p+q, ldC = p+q)
# uX1 = -Z11 - bzs_11
# = -(r*zs*r')_11 - bzs_11
# uX2 = -Z22 - bzs_22
# = -(r*zs*r')_22 - bzs_22
blas.copy(bz11, x[1])
blas.copy(bz22, x[2])
# scale diagonal of zs by 1/2
blas.scal(0.5, z, inc = p+q+1, offset = m)
# a := r*tril(zs)
blas.copy(r, a)
blas.trmm(z, a, side = 'R', m = p+q, n = p+q, ldA = p+q, ldB =
p+q, offsetA = m)
# x[1] := -x[1] - a[:q,:] * r[:q, :]' - r[:q,:] * a[:q,:]'
# = -bzs_11 - (r*zs*r')_11
blas.syr2k(a, r, x[1], n = q, alpha = -1.0, beta = -1.0)
# x[2] := -x[2] - a[q:,:] * r[q:, :]' - r[q:,:] * a[q:,:]'
# = -bzs_22 - (r*zs*r')_22
blas.syr2k(a, r, x[2], n = p, alpha = -1.0, beta = -1.0,
offsetA = q, offsetB = q)
# scale diagonal of zs by 1/2
blas.scal(2.0, z, inc = p+q+1, offset = m)
def solve_phase1(self,kktsolver='chol',MM = 1e5):
"""
Solves primal Phase I problem using the feasible
start solver.
Returns primal feasible X.
"""
from cvxopt import cholmod, amd
k = 1e-3
# compute Schur complement matrix
Id = [i*(self.n+1) for i in range(self.n)]
As = self._A[:,1:]
As[Id,:] /= sqrt(2.0)
M = spmatrix([],[],[],(self.m,self.m))
base.syrk(As,M,trans='T')
u = +self.b
# compute least-norm solution
F = cholmod.symbolic(M)
cholmod.numeric(M,F)
cholmod.solve(F,u)
x = 0.5*self._A[:,1:]*u
X0 = spmatrix(x[self.V[:].I],self.V.I,self.V.J,(self.n,self.n))
# test feasibility
p = amd.order(self.V)
#Xc,Nf = chompack.embed(X0,p)
#E = chompack.project(Xc,spmatrix(1.0,range(self.n),range(self.n)))
symb = chompack.symbolic(self.V,p)
Xc = chompack.cspmatrix(symb) + X0
try:
# L = chompack.completion(Xc)
L = Xc.copy()
chompack.completion(L)
# least-norm solution is feasible
return X0,None
except:
pass
# create Phase I SDP object
trA = matrix(0.0,(self.m+1,1))
e = matrix(1.0,(self.n,1))
Aa = self._A[Id,1:]
base.gemv(Aa,e,trA,trans='T')
trA[-1] = MM
P1 = SDP()
P1._A = misc.phase1_sdp(self._A,trA)
P1._b = matrix([self.b-k*trA[:self.m],MM])
P1._agg_sparsity()
# find feasible starting point for Phase I problem
tMIN = 0.0
tMAX = 1.0
while True:
t = (tMIN+tMAX)/2.0
#Xt = chompack.copy(Xc)
#chompack.axpy(E,Xt,t)
Xt = Xc.copy() + spmatrix(t,list(range(self.n)),list(range(self.n)))
try:
# L = chompack.completion(Xt)
L = Xt.copy()
chompack.completion(L)
tMAX = t
if tMAX - tMIN < 1e-1:
break
except:
tMAX *= 2.0
tMIN = t
tt = t + 1.0
U = X0 + spmatrix(tt,list(range(self.n,)),list(range(self.n)))
trU = sum(U[:][Id])
Z0 = spdiag([U,spmatrix([tt+k,MM-trU],[0,1],[0,1],(2,2))])
sol = P1.solve_feas(primalstart = {'x':Z0}, kktsolver = kktsolver)
s = sol['x'][-2,-2] - k
if s > 0:
return None,P1
else:
sol.pop('y')
sol.pop('s')
X0 = sol.pop('x')[:self.n,:self.n]\
- spmatrix(s,list(range(self.n)),list(range(self.n)))
return X0,sol
def f(x, y, z):
"""
Solve
C * ux + G' * uzl - 2*A'(uzs21) = bx
-uzs11 = bX1
-uzs22 = bX2
G * ux - D^2 * uzl = bzl
[ -uX1 -A(ux)' ] [ uzs11 uzs21' ]
[ ] - T * [ ] * T = bzs.
[ -A(ux) -uX2 ] [ uzs21 uzs22 ]
On entry, x = (bx, bX1, bX2) and z = [ bzl; bzs[:] ].
On exit, x = (ux, uX1, uX2) and z = [ D*uzl; (r'*uzs*r)[:] ].
Define X = uzs21, Z = T * uzs * T:
C * ux + G' * uzl - 2*A'(X) = bx
[ 0 X' ] [ bX1 0 ]
T * [ ] * T - Z = T * [ ] * T
[ X 0 ] [ 0 bX2 ]
G * ux - D^2 * uzl = bzl
[ -uX1 -A(ux)' ] [ Z11 Z21' ]
[ ] - [ ] = bzs
[ -A(ux) -uX2 ] [ Z21 Z22 ]
Return x = (ux, uX1, uX2), z = [ D*uzl; (rti'*Z*rti)[:] ].
We use the congruence transformation
[ V1 0 ] [ T11 T21' ] [ V1' 0 ] [ I S' ]
[ ] [ ] [ ] = [ ]
[ 0 V2' ] [ T21 T22 ] [ 0 V2 ] [ S I ]
and the factorization
X + S * X' * S = L( L'(X) )
to write this as
C * ux + G' * uzl - 2*A'(X) = bx
L'(V2^-1 * X * V1^-1) - L^-1(V2' * Z21 * V1') = bX
G * ux - D^2 * uzl = bzl
[ -uX1 -A(ux)' ] [ Z11 Z21' ]
[ ] - [ ] = bzs,
[ -A(ux) -uX2 ] [ Z21 Z22 ]
or
C * ux + Gs' * uuzl - 2*As'(XX) = bx
XX - ZZ21 = bX
Gs * ux - uuzl = D^-1 * bzl
-As(ux) - ZZ21 = bbzs_21
-uX1 - Z11 = bzs_11
-uX2 - Z22 = bzs_22
if we introduce scaled variables
uuzl = D * uzl
XX = L'(V2^-1 * X * V1^-1)
= L'(V2^-1 * uzs21 * V1^-1)
ZZ21 = L^-1(V2' * Z21 * V1')
and define
bbzs_21 = L^-1(V2' * bzs_21 * V1')
[ bX1 0 ]
bX = L^-1( V2' * (T * [ ] * T)_21 * V1').
[ 0 bX2 ]
Eliminating Z21 gives
C * ux + Gs' * uuzl - 2*As'(XX) = bx
Gs * ux - uuzl = D^-1 * bzl
-As(ux) - XX = bbzs_21 - bX
-uX1 - Z11 = bzs_11
-uX2 - Z22 = bzs_22
and eliminating uuzl and XX gives
H * ux = bx + Gs' * D^-1 * bzl + 2*As'(bX - bbzs_21)
Gs * ux - uuzl = D^-1 * bzl
-As(ux) - XX = bbzs_21 - bX
-uX1 - Z11 = bzs_11
-uX2 - Z22 = bzs_22.
In summary, we can use the following algorithm:
1. bXX := bX - bbzs21
[ bX1 0 ]
= L^-1( V2' * ((T * [ ] * T)_21 - bzs_21) * V1')
[ 0 bX2 ]
2. Solve H * ux = bx + Gs' * D^-1 * bzl + 2*As'(bXX).
3. From ux, compute
uuzl = Gs*ux - D^-1 * bzl and
X = V2 * L^-T(-As(ux) + bXX) * V1.
4. Return ux, uuzl,
rti' * Z * rti = r' * [ -bX1, X'; X, -bX2 ] * r
and uX1 = -Z11 - bzs_11, uX2 = -Z22 - bzs_22.
"""
# Save bzs_11, bzs_22, bzs_21.
lapack.lacpy(z, bz11, uplo='L', m=q, n=q, ldA=p + q, offsetA=m)
lapack.lacpy(z, bz21, m=p, n=q, ldA=p + q, offsetA=m + q)
lapack.lacpy(z,
bz22,
uplo='L',
m=p,
n=p,
ldA=p + q,
offsetA=m + (p + q + 1) * q)
# zl := D^-1 * zl
# = D^-1 * bzl
blas.tbmv(W['di'], z, n=m, k=0, ldA=1)
# zs := r' * [ bX1, 0; 0, bX2 ] * r.
# zs := [ bX1, 0; 0, bX2 ]
blas.scal(0.0, z, offset=m)
lapack.lacpy(x[1], z, uplo='L', m=q, n=q, ldB=p + q, offsetB=m)
lapack.lacpy(x[2],
z,
uplo='L',
m=p,
n=p,
ldB=p + q,
offsetB=m + (p + q + 1) * q)
# scale diagonal of zs by 1/2
blas.scal(0.5, z, inc=p + q + 1, offset=m)
# a := tril(zs)*r
blas.copy(r, a)
blas.trmm(z,
a,
side='L',
m=p + q,
n=p + q,
ldA=p + q,
ldB=p + q,
offsetA=m)
# zs := a'*r + r'*a
blas.syr2k(r,
a,
z,
trans='T',
n=p + q,
k=p + q,
ldB=p + q,
ldC=p + q,
offsetC=m)
# bz21 := L^-1( V2' * ((r * zs * r')_21 - bz21) * V1')
#
# [ bX1 0 ]
# = L^-1( V2' * ((T * [ ] * T)_21 - bz21) * V1').
# [ 0 bX2 ]
# a = [ r21 r22 ] * z
# = [ r21 r22 ] * r' * [ bX1, 0; 0, bX2 ] * r
# = [ T21 T22 ] * [ bX1, 0; 0, bX2 ] * r
blas.symm(z,
r,
a,
side='R',
m=p,
n=p + q,
ldA=p + q,
ldC=p + q,
offsetB=q)
# bz21 := -bz21 + a * [ r11, r12 ]'
# = -bz21 + (T * [ bX1, 0; 0, bX2 ] * T)_21
blas.gemm(a,
r,
bz21,
transB='T',
m=p,
n=q,
k=p + q,
beta=-1.0,
ldA=p + q,
ldC=p)
# bz21 := V2' * bz21 * V1'
# = V2' * (-bz21 + (T*[bX1, 0; 0, bX2]*T)_21) * V1'
blas.gemm(V2, bz21, tmp, transA='T', m=p, n=q, k=p, ldB=p)
blas.gemm(tmp, V1, bz21, transB='T', m=p, n=q, k=q, ldC=p)
# bz21[:] := D * (I-P) * bz21[:]
# = L^-1 * bz21[:]
# = bXX[:]
blas.copy(bz21, tmp)
base.gemv(P, bz21, tmp, alpha=-1.0, beta=1.0)
base.gemv(D, tmp, bz21)
# Solve H * ux = bx + Gs' * D^-1 * bzl + 2*As'(bXX).
# x[0] := x[0] + Gs'*zl + 2*As'(bz21)
# = bx + G' * D^-1 * bzl + 2 * As'(bXX)
blas.gemv(Gs, z, x[0], trans='T', alpha=1.0, beta=1.0)
blas.gemv(As, bz21, x[0], trans='T', alpha=2.0, beta=1.0)
# x[0] := H \ x[0]
# = ux
lapack.potrs(H, x[0])
# uuzl = Gs*ux - D^-1 * bzl
blas.gemv(Gs, x[0], z, alpha=1.0, beta=-1.0)
# bz21 := V2 * L^-T(-As(ux) + bz21) * V1
# = X
blas.gemv(As, x[0], bz21, alpha=-1.0, beta=1.0)
blas.tbsv(DV, bz21, n=p * q, k=0, ldA=1)
blas.copy(bz21, tmp)
base.gemv(P, tmp, bz21, alpha=-1.0, beta=1.0, trans='T')
blas.gemm(V2, bz21, tmp)
blas.gemm(tmp, V1, bz21)
# zs := -zs + r' * [ 0, X'; X, 0 ] * r
# = r' * [ -bX1, X'; X, -bX2 ] * r.
# a := bz21 * [ r11, r12 ]
# = X * [ r11, r12 ]
blas.gemm(bz21, r, a, m=p, n=p + q, k=q, ldA=p, ldC=p + q)
# z := -z + [ r21, r22 ]' * a + a' * [ r21, r22 ]
# = rti' * uzs * rti
blas.syr2k(r,
a,
z,
trans='T',
beta=-1.0,
n=p + q,
k=p,
offsetA=q,
offsetC=m,
ldB=p + q,
ldC=p + q)
# uX1 = -Z11 - bzs_11
# = -(r*zs*r')_11 - bzs_11
# uX2 = -Z22 - bzs_22
# = -(r*zs*r')_22 - bzs_22
blas.copy(bz11, x[1])
blas.copy(bz22, x[2])
# scale diagonal of zs by 1/2
blas.scal(0.5, z, inc=p + q + 1, offset=m)
# a := r*tril(zs)
blas.copy(r, a)
blas.trmm(z,
a,
side='R',
m=p + q,
n=p + q,
ldA=p + q,
ldB=p + q,
offsetA=m)
# x[1] := -x[1] - a[:q,:] * r[:q, :]' - r[:q,:] * a[:q,:]'
# = -bzs_11 - (r*zs*r')_11
blas.syr2k(a, r, x[1], n=q, alpha=-1.0, beta=-1.0)
# x[2] := -x[2] - a[q:,:] * r[q:, :]' - r[q:,:] * a[q:,:]'
# = -bzs_22 - (r*zs*r')_22
blas.syr2k(a,
r,
x[2],
n=p,
alpha=-1.0,
beta=-1.0,
offsetA=q,
offsetB=q)
# scale diagonal of zs by 1/2
blas.scal(2.0, z, inc=p + q + 1, offset=m)
def F(W):
"""
Custom solver for the system
[ It 0 0 Xt' 0 At1' ... Atk' ][ dwt ] [ rwt ]
[ 0 0 0 -d' 0 0 ... 0 ][ db ] [ rb ]
[ 0 0 0 -I -I 0 ... 0 ][ dv ] [ rv ]
[ Xt -d -I -Wl1^-2 ][ dzl1 ] [ rl1 ]
[ 0 0 -I -Wl2^-2 ][ dzl2 ] = [ rl2 ]
[ At1 0 0 -W1^-2 ][ dz1 ] [ r1 ]
[ | | | . ][ | ] [ | ]
[ Atk 0 0 -Wk^-2 ][ dzk ] [ rk ]
where
It = [ I 0 ] Xt = [ -D*X E ] Ati = [ 0 -e_i' ]
[ 0 0 ] [ -Pi 0 ]
dwt = [ dw ] rwt = [ rw ]
[ dt ] [ rt ].
"""
# scalings and 'intermediate' vectors
# db = inv(Wl1)^2 + inv(Wl2)^2
db = W['di'][:m]**2 + W['di'][m:2*m]**2
dbi = div(1.0,db)
# dt = I - inv(Wl1)*Dbi*inv(Wl1)
dt = 1.0 - mul(W['di'][:m]**2,dbi)
dtsqrt = sqrt(dt)
# lam = Dt*inv(Wl1)*d
lam = mul(dt,mul(W['di'][:m],d))
# lt = E'*inv(Wl1)*lam
lt = matrix(0.0,(k,1))
base.gemv(E, mul(W['di'][:m],lam), lt, trans = 'T')
# Xs = sqrt(Dt)*inv(Wl1)*X
tmp = mul(dtsqrt,W['di'][:m])
Xs = spmatrix(tmp,range(m),range(m))*X
# Es = D*sqrt(Dt)*inv(Wl1)*E
Es = spmatrix(mul(d,tmp),range(m),range(m))*E
# form Ab = I + sum((1/bi)^2*(Pi'*Pi + 4*(v'*v + 1)*Pi'*y*y'*Pi)) + Xs'*Xs
# and Bb = -sum((1/bi)^2*(4*ui*v'*v*Pi'*y*ei')) - Xs'*Es
# and D2 = Es'*Es + sum((1/bi)^2*(1+4*ui^2*(v'*v - 1))
Ab = matrix(0.0,(n,n))
Ab[::n+1] = 1.0
base.syrk(Xs,Ab,trans = 'T', beta = 1.0)
Bb = matrix(0.0,(n,k))
Bb = -Xs.T*Es # inefficient!?
D2 = spmatrix(0.0,range(k),range(k))
base.syrk(Es,D2,trans = 'T', partial = True)
d2 = +D2.V
del D2
py = matrix(0.0,(n,1))
for i in range(k):
binvsq = (1.0/W['beta'][i])**2
Ab += binvsq*Pt[i]
dvv = blas.dot(W['v'][i],W['v'][i])
blas.gemv(P[i], W['v'][i][1:], py, trans = 'T', alpha = 1.0, beta = 0.0)
blas.syrk(py, Ab, alpha = 4*binvsq*(dvv+1), beta = 1.0)
Bb[:,i] -= 4*binvsq*W['v'][i][0]*dvv*py
d2[i] += binvsq*(1+4*(W['v'][i][0]**2)*(dvv-1))
d2i = div(1.0,d2)
d2isqrt = sqrt(d2i)
# compute a = alpha - lam'*inv(Wl1)*E*inv(D2)*E'*inv(Wl1)*lam
alpha = blas.dot(lam,mul(W['di'][:m],d))
tmp = matrix(0.0,(k,1))
base.gemv(E,mul(W['di'][:m],lam), tmp, trans = 'T')
tmp = mul(tmp, d2isqrt) #tmp = inv(D2)^(1/2)*E'*inv(Wl1)*lam
a = alpha - blas.dot(tmp,tmp)
# compute M12 = X'*D*inv(Wl1)*lam + Bb*inv(D2)*E'*inv(Wl1)*lam
tmp = mul(tmp, d2isqrt)
M12 = matrix(0.0,(n,1))
blas.gemv(Bb,tmp,M12, alpha = 1.0)
tmp = mul(d,mul(W['di'][:m],lam))
blas.gemv(X,tmp,M12, trans = 'T', alpha = 1.0, beta = 1.0)
# form and factor M
sBb = Bb * spmatrix(d2isqrt,range(k), range(k))
base.syrk(sBb, Ab, alpha = -1.0, beta = 1.0)
M = matrix([[Ab, M12.T],[M12, a]])
lapack.potrf(M)
def f(x,y,z):
# residuals
rwt = x[:n+k]
rb = x[n+k]
rv = x[n+k+1:n+k+1+m]
iw_rl1 = mul(W['di'][:m],z[:m])
iw_rl2 = mul(W['di'][m:2*m],z[m:2*m])
ri = [z[2*m+i*(n+1):2*m+(i+1)*(n+1)] for i in range(k)]
# compute 'derived' residuals
# rbwt = rwt + sum(Ai'*inv(Wi)^2*ri) + [-X'*D; E']*inv(Wl1)^2*rl1
rbwt = +rwt
for i in range(k):
tmp = +ri[i]
qscal(tmp,W['beta'][i],W['v'][i],inv=True)
qscal(tmp,W['beta'][i],W['v'][i],inv=True)
rbwt[n+i] -= tmp[0]
blas.gemv(P[i], tmp[1:], rbwt, trans = 'T', alpha = -1.0, beta = 1.0)
tmp = mul(W['di'][:m],iw_rl1)
tmp2 = matrix(0.0,(k,1))
base.gemv(E,tmp,tmp2,trans='T')
rbwt[n:] += tmp2
tmp = mul(d,tmp) # tmp = D*inv(Wl1)^2*rl1
blas.gemv(X,tmp,rbwt,trans='T', alpha = -1.0, beta = 1.0)
# rbb = rb - d'*inv(Wl1)^2*rl1
rbb = rb - sum(tmp)
# rbv = rv - inv(Wl2)*rl2 - inv(Wl1)^2*rl1
rbv = rv - mul(W['di'][m:2*m],iw_rl2) - mul(W['di'][:m],iw_rl1)
# [rtw;rtt] = rbwt + [-X'*D; E']*inv(Wl1)^2*inv(Db)*rbv
tmp = mul(W['di'][:m]**2, mul(dbi,rbv))
rtt = +rbwt[n:]
base.gemv(E, tmp, rtt, trans = 'T', alpha = 1.0, beta = 1.0)
rtw = +rbwt[:n]
tmp = mul(d,tmp)
blas.gemv(X, tmp, rtw, trans = 'T', alpha = -1.0, beta = 1.0)
# rtb = rbb - d'*inv(Wl1)^2*inv(Db)*rbv
rtb = rbb - sum(tmp)
# solve M*[dw;db] = [rtw - Bb*inv(D2)*rtt; rtb + lt'*inv(D2)*rtt]
tmp = mul(d2i,rtt)
tmp2 = matrix(0.0,(n,1))
blas.gemv(Bb,tmp,tmp2)
dwdb = matrix([rtw - tmp2,rtb + blas.dot(mul(d2i,lt),rtt)])
lapack.potrs(M,dwdb)
# compute dt = inv(D2)*(rtt - Bb'*dw + lt*db)
tmp2 = matrix(0.0,(k,1))
blas.gemv(Bb, dwdb[:n], tmp2, trans='T')
dt = mul(d2i, rtt - tmp2 + lt*dwdb[-1])
# compute dv = inv(Db)*(rbv + inv(Wl1)^2*(E*dt - D*X*dw - d*db))
dv = matrix(0.0,(m,1))
blas.gemv(X,dwdb[:n],dv,alpha = -1.0)
dv = mul(d,dv) - d*dwdb[-1]
base.gemv(E, dt, dv, beta = 1.0)
tmp = +dv # tmp = E*dt - D*X*dw - d*db
dv = mul(dbi, rbv + mul(W['di'][:m]**2,dv))
# compute wdz1 = inv(Wl1)*(E*dt - D*X*dw - d*db - dv - rl1)
wdz1 = mul(W['di'][:m], tmp - dv) - iw_rl1
# compute wdz2 = - inv(Wl2)*(dv + rl2)
wdz2 = - mul(W['di'][m:2*m],dv) - iw_rl2
# compute wdzi = inv(Wi)*([-ei'*dt; -Pi*dw] - ri)
wdzi = []
tmp = matrix(0.0,(n,1))
for i in range(k):
blas.gemv(P[i],dwdb[:n],tmp, alpha = -1.0, beta = 0.0)
tmp1 = matrix([-dt[i],tmp])
blas.axpy(ri[i],tmp1,alpha = -1.0)
qscal(tmp1,W['beta'][i],W['v'][i],inv=True)
wdzi.append(tmp1)
# solution
x[:n] = dwdb[:n]
x[n:n+k] = dt
x[n+k] = dwdb[-1]
x[n+k+1:] = dv
z[:m] = wdz1
z[m:2*m] = wdz2
for i in range(k):
z[2*m+i*(n+1):2*m+(i+1)*(n+1)] = wdzi[i]
return f
def f(x,y,z):
# residuals
rwt = x[:n+k]
rb = x[n+k]
rv = x[n+k+1:n+k+1+m]
iw_rl1 = mul(W['di'][:m],z[:m])
iw_rl2 = mul(W['di'][m:2*m],z[m:2*m])
ri = [z[2*m+i*(n+1):2*m+(i+1)*(n+1)] for i in range(k)]
# compute 'derived' residuals
# rbwt = rwt + sum(Ai'*inv(Wi)^2*ri) + [-X'*D; E']*inv(Wl1)^2*rl1
rbwt = +rwt
for i in range(k):
tmp = +ri[i]
qscal(tmp,W['beta'][i],W['v'][i],inv=True)
qscal(tmp,W['beta'][i],W['v'][i],inv=True)
rbwt[n+i] -= tmp[0]
blas.gemv(P[i], tmp[1:], rbwt, trans = 'T', alpha = -1.0, beta = 1.0)
tmp = mul(W['di'][:m],iw_rl1)
tmp2 = matrix(0.0,(k,1))
base.gemv(E,tmp,tmp2,trans='T')
rbwt[n:] += tmp2
tmp = mul(d,tmp) # tmp = D*inv(Wl1)^2*rl1
blas.gemv(X,tmp,rbwt,trans='T', alpha = -1.0, beta = 1.0)
# rbb = rb - d'*inv(Wl1)^2*rl1
rbb = rb - sum(tmp)
# rbv = rv - inv(Wl2)*rl2 - inv(Wl1)^2*rl1
rbv = rv - mul(W['di'][m:2*m],iw_rl2) - mul(W['di'][:m],iw_rl1)
# [rtw;rtt] = rbwt + [-X'*D; E']*inv(Wl1)^2*inv(Db)*rbv
tmp = mul(W['di'][:m]**2, mul(dbi,rbv))
rtt = +rbwt[n:]
base.gemv(E, tmp, rtt, trans = 'T', alpha = 1.0, beta = 1.0)
rtw = +rbwt[:n]
tmp = mul(d,tmp)
blas.gemv(X, tmp, rtw, trans = 'T', alpha = -1.0, beta = 1.0)
# rtb = rbb - d'*inv(Wl1)^2*inv(Db)*rbv
rtb = rbb - sum(tmp)
# solve M*[dw;db] = [rtw - Bb*inv(D2)*rtt; rtb + lt'*inv(D2)*rtt]
tmp = mul(d2i,rtt)
tmp2 = matrix(0.0,(n,1))
blas.gemv(Bb,tmp,tmp2)
dwdb = matrix([rtw - tmp2,rtb + blas.dot(mul(d2i,lt),rtt)])
lapack.potrs(M,dwdb)
# compute dt = inv(D2)*(rtt - Bb'*dw + lt*db)
tmp2 = matrix(0.0,(k,1))
blas.gemv(Bb, dwdb[:n], tmp2, trans='T')
dt = mul(d2i, rtt - tmp2 + lt*dwdb[-1])
# compute dv = inv(Db)*(rbv + inv(Wl1)^2*(E*dt - D*X*dw - d*db))
dv = matrix(0.0,(m,1))
blas.gemv(X,dwdb[:n],dv,alpha = -1.0)
dv = mul(d,dv) - d*dwdb[-1]
base.gemv(E, dt, dv, beta = 1.0)
tmp = +dv # tmp = E*dt - D*X*dw - d*db
dv = mul(dbi, rbv + mul(W['di'][:m]**2,dv))
# compute wdz1 = inv(Wl1)*(E*dt - D*X*dw - d*db - dv - rl1)
wdz1 = mul(W['di'][:m], tmp - dv) - iw_rl1
# compute wdz2 = - inv(Wl2)*(dv + rl2)
wdz2 = - mul(W['di'][m:2*m],dv) - iw_rl2
# compute wdzi = inv(Wi)*([-ei'*dt; -Pi*dw] - ri)
wdzi = []
tmp = matrix(0.0,(n,1))
for i in range(k):
blas.gemv(P[i],dwdb[:n],tmp, alpha = -1.0, beta = 0.0)
tmp1 = matrix([-dt[i],tmp])
blas.axpy(ri[i],tmp1,alpha = -1.0)
qscal(tmp1,W['beta'][i],W['v'][i],inv=True)
wdzi.append(tmp1)
# solution
x[:n] = dwdb[:n]
x[n:n+k] = dt
x[n+k] = dwdb[-1]
x[n+k+1:] = dv
z[:m] = wdz1
z[m:2*m] = wdz2
for i in range(k):
z[2*m+i*(n+1):2*m+(i+1)*(n+1)] = wdzi[i]
def f(x, y, z):
# residuals
rwt = x[:n + k]
rb = x[n + k]
rv = x[n + k + 1:n + k + 1 + m]
iw_rl1 = mul(W['di'][:m], z[:m])
iw_rl2 = mul(W['di'][m:2 * m], z[m:2 * m])
ri = [
z[2 * m + i * (n + 1):2 * m + (i + 1) * (n + 1)]
for i in range(k)
]
# compute 'derived' residuals
# rbwt = rwt + sum(Ai'*inv(Wi)^2*ri) + [-X'*D; E']*inv(Wl1)^2*rl1
rbwt = +rwt
for i in range(k):
tmp = +ri[i]
qscal(tmp, W['beta'][i], W['v'][i], inv=True)
qscal(tmp, W['beta'][i], W['v'][i], inv=True)
rbwt[n + i] -= tmp[0]
blas.gemv(P[i], tmp[1:], rbwt, trans='T', alpha=-1.0, beta=1.0)
tmp = mul(W['di'][:m], iw_rl1)
tmp2 = matrix(0.0, (k, 1))
base.gemv(E, tmp, tmp2, trans='T')
rbwt[n:] += tmp2
tmp = mul(d, tmp) # tmp = D*inv(Wl1)^2*rl1
blas.gemv(X, tmp, rbwt, trans='T', alpha=-1.0, beta=1.0)
# rbb = rb - d'*inv(Wl1)^2*rl1
rbb = rb - sum(tmp)
# rbv = rv - inv(Wl2)*rl2 - inv(Wl1)^2*rl1
rbv = rv - mul(W['di'][m:2 * m], iw_rl2) - mul(W['di'][:m], iw_rl1)
# [rtw;rtt] = rbwt + [-X'*D; E']*inv(Wl1)^2*inv(Db)*rbv
tmp = mul(W['di'][:m]**2, mul(dbi, rbv))
rtt = +rbwt[n:]
base.gemv(E, tmp, rtt, trans='T', alpha=1.0, beta=1.0)
rtw = +rbwt[:n]
tmp = mul(d, tmp)
blas.gemv(X, tmp, rtw, trans='T', alpha=-1.0, beta=1.0)
# rtb = rbb - d'*inv(Wl1)^2*inv(Db)*rbv
rtb = rbb - sum(tmp)
# solve M*[dw;db] = [rtw - Bb*inv(D2)*rtt; rtb + lt'*inv(D2)*rtt]
tmp = mul(d2i, rtt)
tmp2 = matrix(0.0, (n, 1))
blas.gemv(Bb, tmp, tmp2)
dwdb = matrix([rtw - tmp2, rtb + blas.dot(mul(d2i, lt), rtt)])
lapack.potrs(M, dwdb)
# compute dt = inv(D2)*(rtt - Bb'*dw + lt*db)
tmp2 = matrix(0.0, (k, 1))
blas.gemv(Bb, dwdb[:n], tmp2, trans='T')
dt = mul(d2i, rtt - tmp2 + lt * dwdb[-1])
# compute dv = inv(Db)*(rbv + inv(Wl1)^2*(E*dt - D*X*dw - d*db))
dv = matrix(0.0, (m, 1))
blas.gemv(X, dwdb[:n], dv, alpha=-1.0)
dv = mul(d, dv) - d * dwdb[-1]
base.gemv(E, dt, dv, beta=1.0)
tmp = +dv # tmp = E*dt - D*X*dw - d*db
dv = mul(dbi, rbv + mul(W['di'][:m]**2, dv))
# compute wdz1 = inv(Wl1)*(E*dt - D*X*dw - d*db - dv - rl1)
wdz1 = mul(W['di'][:m], tmp - dv) - iw_rl1
# compute wdz2 = - inv(Wl2)*(dv + rl2)
wdz2 = -mul(W['di'][m:2 * m], dv) - iw_rl2
# compute wdzi = inv(Wi)*([-ei'*dt; -Pi*dw] - ri)
wdzi = []
tmp = matrix(0.0, (n, 1))
for i in range(k):
blas.gemv(P[i], dwdb[:n], tmp, alpha=-1.0, beta=0.0)
tmp1 = matrix([-dt[i], tmp])
blas.axpy(ri[i], tmp1, alpha=-1.0)
qscal(tmp1, W['beta'][i], W['v'][i], inv=True)
wdzi.append(tmp1)
# solution
x[:n] = dwdb[:n]
x[n:n + k] = dt
x[n + k] = dwdb[-1]
x[n + k + 1:] = dv
z[:m] = wdz1
z[m:2 * m] = wdz2
for i in range(k):
z[2 * m + i * (n + 1):2 * m + (i + 1) * (n + 1)] = wdzi[i]
def _gen_randsdp(self, V, m, d, seed):
"""
Random data generator
"""
setseed(seed)
n = self._n
V = chompack.tril(V)
N = len(V)
I = V.I
J = V.J
Il = misc.sub2ind((n, n), I, J)
Id = matrix([i for i in xrange(len(Il)) if I[i] == J[i]])
# generate random y with norm 1
y0 = normal(m, 1)
y0 /= blas.nrm2(y0)
# generate random S0, X0
S0 = mk_rand(V, cone='posdef', seed=seed)
X0 = mk_rand(V, cone='completable', seed=seed)
# generate random A1,...,Am
if type(d) is float:
nz = min(max(1, int(round(d * N))), N)
A = sparse(
[[
spmatrix(normal(N, 1), Il, [0 for i in xrange(N)],
(n**2, 1))
],
[
spmatrix(
normal(nz * m, 1),
[i for j in xrange(m) for i in random.sample(Il, nz)],
[j for j in xrange(m) for i in xrange(nz)], (n**2, m))
]])
elif type(d) is list:
if len(d) == m:
nz = [min(max(1, int(round(v * N))), N) for v in d]
nnz = sum(nz)
A = sparse(
[[
spmatrix(normal(N, 1), Il, [0 for i in xrange(N)],
(n**2, 1))
],
[
spmatrix(normal(nnz, 1), [
i for j in xrange(m)
for i in random.sample(Il, nz[j])
], [j for j in xrange(m) for i in xrange(nz[j])],
(n**2, m))
]])
else:
raise TypeError
# compute A0
u = +S0.V
for k in xrange(m):
base.gemv(A[:, k + 1][Il], matrix(y0[k]), u, beta=1.0, trans='N')
A[Il, 0] = u
self._A = A
# compute b
X0[Il[Id]] *= 0.5
self._b = matrix(0., (m, 1))
u = matrix(0.)
for k in xrange(m):
base.gemv(A[:, k + 1][Il], X0.V, u, trans='T', alpha=2.0)
self._b[k] = u
def Fgp(x=None, z=None):
if x is None: return mnl, matrix(0.0, (n, 1))
f = matrix(0.0, (mnl + 1, 1))
Df = matrix(0.0, (mnl + 1, n))
# y = F*x+g
blas.copy(g, y)
base.gemv(F, x, y, beta=1.0)
if z is not None: H = matrix(0.0, (n, n))
for i, start, stop in ind:
# yi := exp(yi) = exp(Fi*x+gi)
ymax = max(y[start:stop])
y[start:stop] = base.exp(y[start:stop] - ymax)
# fi = log sum yi = log sum exp(Fi*x+gi)
ysum = blas.asum(y, n=stop - start, offset=start)
f[i] = ymax + math.log(ysum)
# yi := yi / sum(yi) = exp(Fi*x+gi) / sum(exp(Fi*x+gi))
blas.scal(1.0 / ysum, y, n=stop - start, offset=start)
# gradfi := Fi' * yi
# = Fi' * exp(Fi*x+gi) / sum(exp(Fi*x+gi))
base.gemv(F,
y,
Df,
trans='T',
m=stop - start,
incy=mnl + 1,
offsetA=start,
offsetx=start,
offsety=i)
if z is not None:
# Hi = Fi' * (diag(yi) - yi*yi') * Fi
# = Fisc' * Fisc
# where
# Fisc = diag(yi)^1/2 * (I - 1*yi') * Fi
# = diag(yi)^1/2 * (Fi - 1*gradfi')
Fsc[:K[i], :] = F[start:stop, :]
for k in range(start, stop):
blas.axpy(Df,
Fsc,
n=n,
alpha=-1.0,
incx=mnl + 1,
incy=Fsc.size[0],
offsetx=i,
offsety=k - start)
blas.scal(math.sqrt(y[k]),
Fsc,
inc=Fsc.size[0],
offset=k - start)
# H += z[i]*Hi = z[i] * Fisc' * Fisc
blas.syrk(Fsc,
H,
trans='T',
k=stop - start,
alpha=z[i],
beta=1.0)
if z is None:
return f, Df
return f, Df, H
def fA(x, y, trans='N', alpha=1.0, beta=0.0):
base.gemv(A, x, y, trans=trans, alpha=alpha, beta=beta)
def solve(x, y, z):
# Solve
#
# [ H A' GG'*W^{-1} ] [ ux ] [ bx ]
# [ A 0 0 ] * [ uy ] = [ by ]
# [ W^{-T}*GG 0 -I ] [ W*uz ] [ W^{-T}*bz ]
#
# and return ux, uy, W*uz.
#
# If not F['singular']:
#
# K*uy = A * S^{-1} * ( bx + GG'*W^{-1}*W^{-T}*bz ) - by
# S*ux = bx + GG'*W^{-1}*W^{-T}*bz - A'*uy
# W*uz = W^{-T} * ( GG*ux - bz ).
#
# If F['singular']:
#
# K*uy = A * S^{-1} * ( bx + GG'*W^{-1}*W^{-T}*bz + A'*by )
# - by
# S*ux = bx + GG'*W^{-1}*W^{-T}*bz + A'*by - A'*y.
# W*uz = W^{-T} * ( GG*ux - bz ).
# z := W^{-1} * z = W^{-1} * bz
scale(z, W, trans='T', inverse='I')
# If not F['singular']:
# x := L^{-1} * P * (x + GGs'*z)
# = L^{-1} * P * (x + GG'*W^{-1}*W^{-T}*bz)
#
# If F['singular']:
# x := L^{-1} * P * (x + GGs'*z + A'*y))
# = L^{-1} * P * (x + GG'*W^{-1}*W^{-T}*bz + A'*y)
if mnl:
base.gemv(F['Dfs'], z, x, trans='T', beta=1.0)
base.gemv(F['Gs'], z, x, offsetx=mnl, trans='T',
beta=1.0)
if F['singular']:
base.gemv(A, y, x, trans='T', beta=1.0)
if type(F['S']) is matrix:
blas.trsv(F['S'], x)
else:
cholmod.solve(F['Sf'], x, sys=7)
cholmod.solve(F['Sf'], x, sys=4)
# y := K^{-1} * (Asc*x - y)
# = K^{-1} * (A * S^{-1} * (bx + GG'*W^{-1}*W^{-T}*bz) - by)
# (if not F['singular'])
# = K^{-1} * (A * S^{-1} * (bx + GG'*W^{-1}*W^{-T}*bz +
# A'*by) - by)
# (if F['singular']).
base.gemv(Asct, x, y, trans='T', beta=-1.0)
if type(F['K']) is matrix:
lapack.potrs(F['K'], y)
else:
cholmod.solve(Kf, y)
# x := P' * L^{-T} * (x - Asc'*y)
# = S^{-1} * (bx + GG'*W^{-1}*W^{-T}*bz - A'*y)
# (if not F['singular'])
# = S^{-1} * (bx + GG'*W^{-1}*W^{-T}*bz + A'*by - A'*y)
# (if F['singular'])
base.gemv(Asct, y, x, alpha=-1.0, beta=1.0)
if type(F['S']) is matrix:
blas.trsv(F['S'], x, trans='T')
else:
cholmod.solve(F['Sf'], x, sys=5)
cholmod.solve(F['Sf'], x, sys=8)
# W*z := GGs*x - z = W^{-T} * (GG*x - bz)
if mnl:
base.gemv(F['Dfs'], x, z, beta=-1.0)
base.gemv(F['Gs'], x, z, beta=-1.0, offsety=mnl)
def F(W):
"""
Custom solver for the system
[ It 0 0 Xt' 0 At1' ... Atk' ][ dwt ] [ rwt ]
[ 0 0 0 -d' 0 0 ... 0 ][ db ] [ rb ]
[ 0 0 0 -I -I 0 ... 0 ][ dv ] [ rv ]
[ Xt -d -I -Wl1^-2 ][ dzl1 ] [ rl1 ]
[ 0 0 -I -Wl2^-2 ][ dzl2 ] = [ rl2 ]
[ At1 0 0 -W1^-2 ][ dz1 ] [ r1 ]
[ | | | . ][ | ] [ | ]
[ Atk 0 0 -Wk^-2 ][ dzk ] [ rk ]
where
It = [ I 0 ] Xt = [ -D*X E ] Ati = [ 0 -e_i' ]
[ 0 0 ] [ -Pi 0 ]
dwt = [ dw ] rwt = [ rw ]
[ dt ] [ rt ].
"""
# scalings and 'intermediate' vectors
# db = inv(Wl1)^2 + inv(Wl2)^2
db = W['di'][:m]**2 + W['di'][m:2 * m]**2
dbi = div(1.0, db)
# dt = I - inv(Wl1)*Dbi*inv(Wl1)
dt = 1.0 - mul(W['di'][:m]**2, dbi)
dtsqrt = sqrt(dt)
# lam = Dt*inv(Wl1)*d
lam = mul(dt, mul(W['di'][:m], d))
# lt = E'*inv(Wl1)*lam
lt = matrix(0.0, (k, 1))
base.gemv(E, mul(W['di'][:m], lam), lt, trans='T')
# Xs = sqrt(Dt)*inv(Wl1)*X
tmp = mul(dtsqrt, W['di'][:m])
Xs = spmatrix(tmp, range(m), range(m)) * X
# Es = D*sqrt(Dt)*inv(Wl1)*E
Es = spmatrix(mul(d, tmp), range(m), range(m)) * E
# form Ab = I + sum((1/bi)^2*(Pi'*Pi + 4*(v'*v + 1)*Pi'*y*y'*Pi)) + Xs'*Xs
# and Bb = -sum((1/bi)^2*(4*ui*v'*v*Pi'*y*ei')) - Xs'*Es
# and D2 = Es'*Es + sum((1/bi)^2*(1+4*ui^2*(v'*v - 1))
Ab = matrix(0.0, (n, n))
Ab[::n + 1] = 1.0
base.syrk(Xs, Ab, trans='T', beta=1.0)
Bb = matrix(0.0, (n, k))
Bb = -Xs.T * Es # inefficient!?
D2 = spmatrix(0.0, range(k), range(k))
base.syrk(Es, D2, trans='T', partial=True)
d2 = +D2.V
del D2
py = matrix(0.0, (n, 1))
for i in range(k):
binvsq = (1.0 / W['beta'][i])**2
Ab += binvsq * Pt[i]
dvv = blas.dot(W['v'][i], W['v'][i])
blas.gemv(P[i], W['v'][i][1:], py, trans='T', alpha=1.0, beta=0.0)
blas.syrk(py, Ab, alpha=4 * binvsq * (dvv + 1), beta=1.0)
Bb[:, i] -= 4 * binvsq * W['v'][i][0] * dvv * py
d2[i] += binvsq * (1 + 4 * (W['v'][i][0]**2) * (dvv - 1))
d2i = div(1.0, d2)
d2isqrt = sqrt(d2i)
# compute a = alpha - lam'*inv(Wl1)*E*inv(D2)*E'*inv(Wl1)*lam
alpha = blas.dot(lam, mul(W['di'][:m], d))
tmp = matrix(0.0, (k, 1))
base.gemv(E, mul(W['di'][:m], lam), tmp, trans='T')
tmp = mul(tmp, d2isqrt) #tmp = inv(D2)^(1/2)*E'*inv(Wl1)*lam
a = alpha - blas.dot(tmp, tmp)
# compute M12 = X'*D*inv(Wl1)*lam + Bb*inv(D2)*E'*inv(Wl1)*lam
tmp = mul(tmp, d2isqrt)
M12 = matrix(0.0, (n, 1))
blas.gemv(Bb, tmp, M12, alpha=1.0)
tmp = mul(d, mul(W['di'][:m], lam))
blas.gemv(X, tmp, M12, trans='T', alpha=1.0, beta=1.0)
# form and factor M
sBb = Bb * spmatrix(d2isqrt, range(k), range(k))
base.syrk(sBb, Ab, alpha=-1.0, beta=1.0)
M = matrix([[Ab, M12.T], [M12, a]])
lapack.potrf(M)
def f(x, y, z):
# residuals
rwt = x[:n + k]
rb = x[n + k]
rv = x[n + k + 1:n + k + 1 + m]
iw_rl1 = mul(W['di'][:m], z[:m])
iw_rl2 = mul(W['di'][m:2 * m], z[m:2 * m])
ri = [
z[2 * m + i * (n + 1):2 * m + (i + 1) * (n + 1)]
for i in range(k)
]
# compute 'derived' residuals
# rbwt = rwt + sum(Ai'*inv(Wi)^2*ri) + [-X'*D; E']*inv(Wl1)^2*rl1
rbwt = +rwt
for i in range(k):
tmp = +ri[i]
qscal(tmp, W['beta'][i], W['v'][i], inv=True)
qscal(tmp, W['beta'][i], W['v'][i], inv=True)
rbwt[n + i] -= tmp[0]
blas.gemv(P[i], tmp[1:], rbwt, trans='T', alpha=-1.0, beta=1.0)
tmp = mul(W['di'][:m], iw_rl1)
tmp2 = matrix(0.0, (k, 1))
base.gemv(E, tmp, tmp2, trans='T')
rbwt[n:] += tmp2
tmp = mul(d, tmp) # tmp = D*inv(Wl1)^2*rl1
blas.gemv(X, tmp, rbwt, trans='T', alpha=-1.0, beta=1.0)
# rbb = rb - d'*inv(Wl1)^2*rl1
rbb = rb - sum(tmp)
# rbv = rv - inv(Wl2)*rl2 - inv(Wl1)^2*rl1
rbv = rv - mul(W['di'][m:2 * m], iw_rl2) - mul(W['di'][:m], iw_rl1)
# [rtw;rtt] = rbwt + [-X'*D; E']*inv(Wl1)^2*inv(Db)*rbv
tmp = mul(W['di'][:m]**2, mul(dbi, rbv))
rtt = +rbwt[n:]
base.gemv(E, tmp, rtt, trans='T', alpha=1.0, beta=1.0)
rtw = +rbwt[:n]
tmp = mul(d, tmp)
blas.gemv(X, tmp, rtw, trans='T', alpha=-1.0, beta=1.0)
# rtb = rbb - d'*inv(Wl1)^2*inv(Db)*rbv
rtb = rbb - sum(tmp)
# solve M*[dw;db] = [rtw - Bb*inv(D2)*rtt; rtb + lt'*inv(D2)*rtt]
tmp = mul(d2i, rtt)
tmp2 = matrix(0.0, (n, 1))
blas.gemv(Bb, tmp, tmp2)
dwdb = matrix([rtw - tmp2, rtb + blas.dot(mul(d2i, lt), rtt)])
lapack.potrs(M, dwdb)
# compute dt = inv(D2)*(rtt - Bb'*dw + lt*db)
tmp2 = matrix(0.0, (k, 1))
blas.gemv(Bb, dwdb[:n], tmp2, trans='T')
dt = mul(d2i, rtt - tmp2 + lt * dwdb[-1])
# compute dv = inv(Db)*(rbv + inv(Wl1)^2*(E*dt - D*X*dw - d*db))
dv = matrix(0.0, (m, 1))
blas.gemv(X, dwdb[:n], dv, alpha=-1.0)
dv = mul(d, dv) - d * dwdb[-1]
base.gemv(E, dt, dv, beta=1.0)
tmp = +dv # tmp = E*dt - D*X*dw - d*db
dv = mul(dbi, rbv + mul(W['di'][:m]**2, dv))
# compute wdz1 = inv(Wl1)*(E*dt - D*X*dw - d*db - dv - rl1)
wdz1 = mul(W['di'][:m], tmp - dv) - iw_rl1
# compute wdz2 = - inv(Wl2)*(dv + rl2)
wdz2 = -mul(W['di'][m:2 * m], dv) - iw_rl2
# compute wdzi = inv(Wi)*([-ei'*dt; -Pi*dw] - ri)
wdzi = []
tmp = matrix(0.0, (n, 1))
for i in range(k):
blas.gemv(P[i], dwdb[:n], tmp, alpha=-1.0, beta=0.0)
tmp1 = matrix([-dt[i], tmp])
blas.axpy(ri[i], tmp1, alpha=-1.0)
qscal(tmp1, W['beta'][i], W['v'][i], inv=True)
wdzi.append(tmp1)
# solution
x[:n] = dwdb[:n]
x[n:n + k] = dt
x[n + k] = dwdb[-1]
x[n + k + 1:] = dv
z[:m] = wdz1
z[m:2 * m] = wdz2
for i in range(k):
z[2 * m + i * (n + 1):2 * m + (i + 1) * (n + 1)] = wdzi[i]
return f
def solve_phase1(self, kktsolver='chol', MM=1e5):
"""
Solves primal Phase I problem using the feasible
start solver.
Returns primal feasible X.
"""
from cvxopt import cholmod, amd
k = 1e-3
# compute Schur complement matrix
Id = [i * (self.n + 1) for i in range(self.n)]
As = self._A[:, 1:]
As[Id, :] /= sqrt(2.0)
M = spmatrix([], [], [], (self.m, self.m))
base.syrk(As, M, trans='T')
u = +self.b
# compute least-norm solution
F = cholmod.symbolic(M)
cholmod.numeric(M, F)
cholmod.solve(F, u)
x = 0.5 * self._A[:, 1:] * u
X0 = spmatrix(x[self.V[:].I], self.V.I, self.V.J, (self.n, self.n))
# test feasibility
p = amd.order(self.V)
#Xc,Nf = chompack.embed(X0,p)
#E = chompack.project(Xc,spmatrix(1.0,range(self.n),range(self.n)))
symb = chompack.symbolic(self.V, p)
Xc = chompack.cspmatrix(symb) + X0
try:
# L = chompack.completion(Xc)
L = Xc.copy()
chompack.completion(L)
# least-norm solution is feasible
return X0
except:
pass
# create Phase I SDP object
trA = matrix(0.0, (self.m + 1, 1))
e = matrix(1.0, (self.n, 1))
Aa = self._A[Id, 1:]
base.gemv(Aa, e, trA, trans='T')
trA[-1] = MM
P1 = SDP()
P1._A = misc.phase1_sdp(self._A, trA)
P1._b = matrix([self.b - k * trA[:self.m], MM])
P1._agg_sparsity()
# find feasible starting point for Phase I problem
tMIN = 0.0
tMAX = 1.0
while True:
t = (tMIN + tMAX) / 2.0
#Xt = chompack.copy(Xc)
#chompack.axpy(E,Xt,t)
Xt = Xc.copy() + spmatrix(t, range(self.n), range(self.n))
try:
# L = chompack.completion(Xt)
L = Xt.copy()
chompack.completion(L)
tMAX = t
if tMAX - tMIN < 1e-1:
break
except:
tMAX *= 2.0
tMIN = t
tt = t + 1.0
U = X0 + spmatrix(tt, range(self.n, ), range(self.n))
trU = sum(U[:][Id])
Z0 = spdiag([U, spmatrix([tt + k, MM - trU], [0, 1], [0, 1], (2, 2))])
sol = P1.solve_feas(primalstart={'x': Z0}, kktsolver=kktsolver)
s = sol['x'][-2, -2] - k
if s > 0:
return None, P1
else:
sol.pop('y')
sol.pop('s')
X0 = sol.pop('x')[:self.n,:self.n]\
- spmatrix(s,range(self.n),range(self.n))
return X0, sol