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iternsym.c
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iternsym.c
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/**************************************************************************
**
** Copyright (C) 1993 David E. Stewart & Zbigniew Leyk, all rights reserved.
**
** Meschach Library
**
** This Meschach Library is provided "as is" without any express
** or implied warranty of any kind with respect to this software.
** In particular the authors shall not be liable for any direct,
** indirect, special, incidental or consequential damages arising
** in any way from use of the software.
**
** Everyone is granted permission to copy, modify and redistribute this
** Meschach Library, provided:
** 1. All copies contain this copyright notice.
** 2. All modified copies shall carry a notice stating who
** made the last modification and the date of such modification.
** 3. No charge is made for this software or works derived from it.
** This clause shall not be construed as constraining other software
** distributed on the same medium as this software, nor is a
** distribution fee considered a charge.
**
***************************************************************************/
/* iter.c 17/09/93 */
/*
ITERATIVE METHODS - implementation of several iterative methods;
see also iter0.c
*/
#include <stdio.h>
#include <math.h>
#include "matrix.h"
#include "matrix2.h"
#include "sparse.h"
#include "iter.h"
static char rcsid[] = "$Header: iternsym.c,v 1.6 1995/01/30 14:53:01 des Exp $";
#ifdef ANSI_C
VEC *spCHsolve(SPMAT *,VEC *,VEC *);
#else
VEC *spCHsolve();
#endif
/*
iter_cgs -- uses CGS to compute a solution x to A.x=b
*/
#ifndef ANSI_C
VEC *iter_cgs(ip,r0)
ITER *ip;
VEC *r0;
#else
VEC *iter_cgs(ITER *ip, VEC *r0)
#endif
{
STATIC VEC *p = VNULL, *q = VNULL, *r = VNULL, *u = VNULL;
STATIC VEC *v = VNULL, *z = VNULL;
VEC *tmp;
Real alpha, beta, nres, rho, old_rho, sigma, inner;
if (ip == INULL)
error(E_NULL,"iter_cgs");
if (!ip->Ax || !ip->b || !r0)
error(E_NULL,"iter_cgs");
if ( ip->x == ip->b )
error(E_INSITU,"iter_cgs");
if (!ip->stop_crit)
error(E_NULL,"iter_cgs");
if ( r0->dim != ip->b->dim )
error(E_SIZES,"iter_cgs");
if ( ip->eps <= 0.0 ) ip->eps = MACHEPS;
p = v_resize(p,ip->b->dim);
q = v_resize(q,ip->b->dim);
r = v_resize(r,ip->b->dim);
u = v_resize(u,ip->b->dim);
v = v_resize(v,ip->b->dim);
MEM_STAT_REG(p,TYPE_VEC);
MEM_STAT_REG(q,TYPE_VEC);
MEM_STAT_REG(r,TYPE_VEC);
MEM_STAT_REG(u,TYPE_VEC);
MEM_STAT_REG(v,TYPE_VEC);
if (ip->Bx) {
z = v_resize(z,ip->b->dim);
MEM_STAT_REG(z,TYPE_VEC);
}
if (ip->x != VNULL) {
if (ip->x->dim != ip->b->dim)
error(E_SIZES,"iter_cgs");
ip->Ax(ip->A_par,ip->x,v); /* v = A*x */
if (ip->Bx) {
v_sub(ip->b,v,v); /* v = b - A*x */
(ip->Bx)(ip->B_par,v,r); /* r = B*(b-A*x) */
}
else v_sub(ip->b,v,r); /* r = b-A*x */
}
else { /* ip->x == 0 */
ip->x = v_get(ip->b->dim); /* x == 0 */
ip->shared_x = FALSE;
if (ip->Bx) (ip->Bx)(ip->B_par,ip->b,r); /* r = B*b */
else v_copy(ip->b,r); /* r = b */
}
v_zero(p);
v_zero(q);
old_rho = 1.0;
for (ip->steps = 0; ip->steps <= ip->limit; ip->steps++) {
inner = in_prod(r,r);
nres = sqrt(fabs(inner));
if (ip->steps == 0) ip->init_res = nres;
if (ip->info) ip->info(ip,nres,r,VNULL);
if ( ip->stop_crit(ip,nres,r,VNULL) ) break;
rho = in_prod(r0,r);
if ( old_rho == 0.0 )
error(E_BREAKDOWN,"iter_cgs");
beta = rho/old_rho;
v_mltadd(r,q,beta,u);
v_mltadd(q,p,beta,v);
v_mltadd(u,v,beta,p);
(ip->Ax)(ip->A_par,p,q);
if (ip->Bx) {
(ip->Bx)(ip->B_par,q,z);
tmp = z;
}
else tmp = q;
sigma = in_prod(r0,tmp);
if ( sigma == 0.0 )
error(E_BREAKDOWN,"iter_cgs");
alpha = rho/sigma;
v_mltadd(u,tmp,-alpha,q);
v_add(u,q,v);
(ip->Ax)(ip->A_par,v,u);
if (ip->Bx) {
(ip->Bx)(ip->B_par,u,z);
tmp = z;
}
else tmp = u;
v_mltadd(r,tmp,-alpha,r);
v_mltadd(ip->x,v,alpha,ip->x);
old_rho = rho;
}
#ifdef THREADSAFE
V_FREE(p); V_FREE(q); V_FREE(r); V_FREE(u);
V_FREE(v); V_FREE(z);
#endif
return ip->x;
}
/* iter_spcgs -- simple interface for SPMAT data structures
use always as follows:
x = iter_spcgs(A,B,b,r0,tol,x,limit,steps);
or
x = iter_spcgs(A,B,b,r0,tol,VNULL,limit,steps);
In the second case the solution vector is created.
If B is not NULL then it is a preconditioner.
*/
#ifndef ANSI_C
VEC *iter_spcgs(A,B,b,r0,tol,x,limit,steps)
SPMAT *A, *B;
VEC *b, *r0, *x;
double tol;
int *steps,limit;
#else
VEC *iter_spcgs(SPMAT *A, SPMAT *B, VEC *b, VEC *r0, double tol,
VEC *x, int limit, int *steps)
#endif
{
ITER *ip;
ip = iter_get(0,0);
ip->Ax = (Fun_Ax) sp_mv_mlt;
ip->A_par = (void *) A;
if (B) {
ip->Bx = (Fun_Ax) sp_mv_mlt;
ip->B_par = (void *) B;
}
else {
ip->Bx = (Fun_Ax) NULL;
ip->B_par = NULL;
}
ip->info = (Fun_info) NULL;
ip->limit = limit;
ip->b = b;
ip->eps = tol;
ip->x = x;
iter_cgs(ip,r0);
x = ip->x;
if (steps) *steps = ip->steps;
ip->shared_x = ip->shared_b = TRUE;
iter_free(ip); /* release only ITER structure */
return x;
}
/*
Routine for performing LSQR -- the least squares QR algorithm
of Paige and Saunders:
"LSQR: an algorithm for sparse linear equations and
sparse least squares", ACM Trans. Math. Soft., v. 8
pp. 43--71 (1982)
*/
/* iter_lsqr -- sparse CG-like least squares routine:
-- finds min_x ||A.x-b||_2 using A defined through A & AT
-- returns x (if x != NULL) */
#ifndef ANSI_C
VEC *iter_lsqr(ip)
ITER *ip;
#else
VEC *iter_lsqr(ITER *ip)
#endif
{
STATIC VEC *u = VNULL, *v = VNULL, *w = VNULL, *tmp = VNULL;
Real alpha, beta, phi, phi_bar;
Real rho, rho_bar, rho_max, theta, nres;
Real s, c; /* for Givens' rotations */
int m, n;
if ( ! ip || ! ip->b || !ip->Ax || !ip->ATx )
error(E_NULL,"iter_lsqr");
if ( ip->x == ip->b )
error(E_INSITU,"iter_lsqr");
if (!ip->stop_crit || !ip->x)
error(E_NULL,"iter_lsqr");
if ( ip->eps <= 0.0 ) ip->eps = MACHEPS;
m = ip->b->dim;
n = ip->x->dim;
u = v_resize(u,(unsigned int)m);
v = v_resize(v,(unsigned int)n);
w = v_resize(w,(unsigned int)n);
tmp = v_resize(tmp,(unsigned int)n);
MEM_STAT_REG(u,TYPE_VEC);
MEM_STAT_REG(v,TYPE_VEC);
MEM_STAT_REG(w,TYPE_VEC);
MEM_STAT_REG(tmp,TYPE_VEC);
if (ip->x != VNULL) {
ip->Ax(ip->A_par,ip->x,u); /* u = A*x */
v_sub(ip->b,u,u); /* u = b-A*x */
}
else { /* ip->x == 0 */
ip->x = v_get(ip->b->dim);
ip->shared_x = FALSE;
v_copy(ip->b,u); /* u = b */
}
beta = v_norm2(u);
if ( beta == 0.0 ) return ip->x;
sv_mlt(1.0/beta,u,u);
(ip->ATx)(ip->AT_par,u,v);
alpha = v_norm2(v);
if ( alpha == 0.0 ) return ip->x;
sv_mlt(1.0/alpha,v,v);
v_copy(v,w);
phi_bar = beta;
rho_bar = alpha;
rho_max = 1.0;
for (ip->steps = 0; ip->steps <= ip->limit; ip->steps++) {
tmp = v_resize(tmp,m);
(ip->Ax)(ip->A_par,v,tmp);
v_mltadd(tmp,u,-alpha,u);
beta = v_norm2(u);
sv_mlt(1.0/beta,u,u);
tmp = v_resize(tmp,n);
(ip->ATx)(ip->AT_par,u,tmp);
v_mltadd(tmp,v,-beta,v);
alpha = v_norm2(v);
sv_mlt(1.0/alpha,v,v);
rho = sqrt(rho_bar*rho_bar+beta*beta);
if ( rho > rho_max )
rho_max = rho;
c = rho_bar/rho;
s = beta/rho;
theta = s*alpha;
rho_bar = -c*alpha;
phi = c*phi_bar;
phi_bar = s*phi_bar;
/* update ip->x & w */
if ( rho == 0.0 )
error(E_BREAKDOWN,"iter_lsqr");
v_mltadd(ip->x,w,phi/rho,ip->x);
v_mltadd(v,w,-theta/rho,w);
nres = fabs(phi_bar*alpha*c)*rho_max;
if (ip->info) ip->info(ip,nres,w,VNULL);
if (ip->steps == 0) ip->init_res = nres;
if ( ip->stop_crit(ip,nres,w,VNULL) ) break;
}
#ifdef THREADSAFE
V_FREE(u); V_FREE(v); V_FREE(w); V_FREE(tmp);
#endif
return ip->x;
}
/* iter_splsqr -- simple interface for SPMAT data structures */
#ifndef ANSI_C
VEC *iter_splsqr(A,b,tol,x,limit,steps)
SPMAT *A;
VEC *b, *x;
double tol;
int *steps,limit;
#else
VEC *iter_splsqr(SPMAT *A, VEC *b, double tol,
VEC *x, int limit, int *steps)
#endif
{
ITER *ip;
ip = iter_get(0,0);
ip->Ax = (Fun_Ax) sp_mv_mlt;
ip->A_par = (void *) A;
ip->ATx = (Fun_Ax) sp_vm_mlt;
ip->AT_par = (void *) A;
ip->Bx = (Fun_Ax) NULL;
ip->B_par = NULL;
ip->info = (Fun_info) NULL;
ip->limit = limit;
ip->b = b;
ip->eps = tol;
ip->x = x;
iter_lsqr(ip);
x = ip->x;
if (steps) *steps = ip->steps;
ip->shared_x = ip->shared_b = TRUE;
iter_free(ip); /* release only ITER structure */
return x;
}
/* iter_arnoldi -- an implementation of the Arnoldi method;
iterative refinement is applied.
*/
#ifndef ANSI_C
MAT *iter_arnoldi_iref(ip,h_rem,Q,H)
ITER *ip;
Real *h_rem;
MAT *Q, *H;
#else
MAT *iter_arnoldi_iref(ITER *ip, Real *h_rem, MAT *Q, MAT *H)
#endif
{
STATIC VEC *u=VNULL, *r=VNULL, *s=VNULL, *tmp=VNULL;
VEC v; /* auxiliary vector */
int i,j;
Real h_val, c;
if (ip == INULL)
error(E_NULL,"iter_arnoldi_iref");
if ( ! ip->Ax || ! Q || ! ip->x )
error(E_NULL,"iter_arnoldi_iref");
if ( ip->k <= 0 )
error(E_BOUNDS,"iter_arnoldi_iref");
if ( Q->n != ip->x->dim || Q->m != ip->k )
error(E_SIZES,"iter_arnoldi_iref");
m_zero(Q);
H = m_resize(H,ip->k,ip->k);
m_zero(H);
u = v_resize(u,ip->x->dim);
r = v_resize(r,ip->k);
s = v_resize(s,ip->k);
tmp = v_resize(tmp,ip->x->dim);
MEM_STAT_REG(u,TYPE_VEC);
MEM_STAT_REG(r,TYPE_VEC);
MEM_STAT_REG(s,TYPE_VEC);
MEM_STAT_REG(tmp,TYPE_VEC);
v.dim = v.max_dim = ip->x->dim;
c = v_norm2(ip->x);
if ( c <= 0.0)
return H;
else {
v.ve = Q->me[0];
sv_mlt(1.0/c,ip->x,&v);
}
v_zero(r);
v_zero(s);
for ( i = 0; i < ip->k; i++ )
{
v.ve = Q->me[i];
u = (ip->Ax)(ip->A_par,&v,u);
for (j = 0; j <= i; j++) {
v.ve = Q->me[j];
/* modified Gram-Schmidt */
r->ve[j] = in_prod(&v,u);
v_mltadd(u,&v,-r->ve[j],u);
}
h_val = v_norm2(u);
/* if u == 0 then we have an exact subspace */
if ( h_val <= 0.0 )
{
*h_rem = h_val;
return H;
}
/* iterative refinement -- ensures near orthogonality */
do {
v_zero(tmp);
for (j = 0; j <= i; j++) {
v.ve = Q->me[j];
s->ve[j] = in_prod(&v,u);
v_mltadd(tmp,&v,s->ve[j],tmp);
}
v_sub(u,tmp,u);
v_add(r,s,r);
} while ( v_norm2(s) > 0.1*(h_val = v_norm2(u)) );
/* now that u is nearly orthogonal to Q, update H */
set_col(H,i,r);
/* check once again if h_val is zero */
if ( h_val <= 0.0 )
{
*h_rem = h_val;
return H;
}
if ( i == ip->k-1 )
{
*h_rem = h_val;
continue;
}
/* H->me[i+1][i] = h_val; */
m_set_val(H,i+1,i,h_val);
v.ve = Q->me[i+1];
sv_mlt(1.0/h_val,u,&v);
}
#ifdef THREADSAFE
V_FREE(u); V_FREE(r); V_FREE(s); V_FREE(tmp);
#endif
return H;
}
/* iter_arnoldi -- an implementation of the Arnoldi method;
modified Gram-Schmidt algorithm
*/
#ifndef ANSI_C
MAT *iter_arnoldi(ip,h_rem,Q,H)
ITER *ip;
Real *h_rem;
MAT *Q, *H;
#else
MAT *iter_arnoldi(ITER *ip, Real *h_rem, MAT *Q, MAT *H)
#endif
{
STATIC VEC *u=VNULL, *r=VNULL;
VEC v; /* auxiliary vector */
int i,j;
Real h_val, c;
if (ip == INULL)
error(E_NULL,"iter_arnoldi");
if ( ! ip->Ax || ! Q || ! ip->x )
error(E_NULL,"iter_arnoldi");
if ( ip->k <= 0 )
error(E_BOUNDS,"iter_arnoldi");
if ( Q->n != ip->x->dim || Q->m != ip->k )
error(E_SIZES,"iter_arnoldi");
m_zero(Q);
H = m_resize(H,ip->k,ip->k);
m_zero(H);
u = v_resize(u,ip->x->dim);
r = v_resize(r,ip->k);
MEM_STAT_REG(u,TYPE_VEC);
MEM_STAT_REG(r,TYPE_VEC);
v.dim = v.max_dim = ip->x->dim;
c = v_norm2(ip->x);
if ( c <= 0.0)
return H;
else {
v.ve = Q->me[0];
sv_mlt(1.0/c,ip->x,&v);
}
v_zero(r);
for ( i = 0; i < ip->k; i++ )
{
v.ve = Q->me[i];
u = (ip->Ax)(ip->A_par,&v,u);
for (j = 0; j <= i; j++) {
v.ve = Q->me[j];
/* modified Gram-Schmidt */
r->ve[j] = in_prod(&v,u);
v_mltadd(u,&v,-r->ve[j],u);
}
h_val = v_norm2(u);
/* if u == 0 then we have an exact subspace */
if ( h_val <= 0.0 )
{
*h_rem = h_val;
return H;
}
set_col(H,i,r);
if ( i == ip->k-1 )
{
*h_rem = h_val;
continue;
}
/* H->me[i+1][i] = h_val; */
m_set_val(H,i+1,i,h_val);
v.ve = Q->me[i+1];
sv_mlt(1.0/h_val,u,&v);
}
#ifdef THREADSAFE
V_FREE(u); V_FREE(r);
#endif
return H;
}
/* iter_sparnoldi -- uses arnoldi() with an explicit representation of A */
#ifndef ANSI_C
MAT *iter_sparnoldi(A,x0,m,h_rem,Q,H)
SPMAT *A;
VEC *x0;
int m;
Real *h_rem;
MAT *Q, *H;
#else
MAT *iter_sparnoldi(SPMAT *A, VEC *x0, int m, Real *h_rem, MAT *Q, MAT *H)
#endif
{
ITER *ip;
ip = iter_get(0,0);
ip->Ax = (Fun_Ax) sp_mv_mlt;
ip->A_par = (void *) A;
ip->x = x0;
ip->k = m;
iter_arnoldi_iref(ip,h_rem,Q,H);
ip->shared_x = ip->shared_b = TRUE;
iter_free(ip); /* release only ITER structure */
return H;
}
/* for testing gmres */
#ifndef ANSI_C
static void test_gmres(ip,i,Q,R,givc,givs,h_val)
ITER *ip;
int i;
MAT *Q, *R;
VEC *givc, *givs;
double h_val;
#else
static void test_gmres(ITER *ip, int i, MAT *Q, MAT *R,
VEC *givc, VEC *givs, double h_val)
#endif
{
VEC vt, vt1;
STATIC MAT *Q1=MNULL, *R1=MNULL;
int j;
/* test Q*A*Q^T = R */
Q = m_resize(Q,i+1,ip->b->dim);
Q1 = m_resize(Q1,i+1,ip->b->dim);
R1 = m_resize(R1,i+1,i+1);
MEM_STAT_REG(Q1,TYPE_MAT);
MEM_STAT_REG(R1,TYPE_MAT);
vt.dim = vt.max_dim = ip->b->dim;
vt1.dim = vt1.max_dim = ip->b->dim;
for (j=0; j <= i; j++) {
vt.ve = Q->me[j];
vt1.ve = Q1->me[j];
ip->Ax(ip->A_par,&vt,&vt1);
}
mmtr_mlt(Q,Q1,R1);
R1 = m_resize(R1,i+2,i+1);
for (j=0; j < i; j++)
R1->me[i+1][j] = 0.0;
R1->me[i+1][i] = h_val;
for (j = 0; j <= i; j++) {
rot_rows(R1,j,j+1,givc->ve[j],givs->ve[j],R1);
}
R1 = m_resize(R1,i+1,i+1);
m_sub(R,R1,R1);
/* if (m_norm_inf(R1) > MACHEPS*ip->b->dim) */
#ifndef MEX
printf(" %d. ||Q*A*Q^T - H|| = %g [cf. MACHEPS = %g]\n",
ip->steps,m_norm_inf(R1),MACHEPS);
#endif
/* check Q*Q^T = I */
Q = m_resize(Q,i+1,ip->b->dim);
mmtr_mlt(Q,Q,R1);
for (j=0; j <= i; j++)
R1->me[j][j] -= 1.0;
#ifndef MEX
if (m_norm_inf(R1) > MACHEPS*ip->b->dim)
printf(" ! m_norm_inf(Q*Q^T) = %g\n",m_norm_inf(R1));
#endif
#ifdef THREADSAFE
M_FREE(Q1); M_FREE(R1);
#endif
}
/* gmres -- generalised minimum residual algorithm of Saad & Schultz
SIAM J. Sci. Stat. Comp. v.7, pp.856--869 (1986)
*/
#ifndef ANSI_C
VEC *iter_gmres(ip)
ITER *ip;
#else
VEC *iter_gmres(ITER *ip)
#endif
{
STATIC VEC *u=VNULL, *r=VNULL, *rhs = VNULL;
STATIC VEC *givs=VNULL, *givc=VNULL, *z = VNULL;
STATIC MAT *Q = MNULL, *R = MNULL;
VEC *rr, v, v1; /* additional pointers (not real vectors) */
int i,j, done;
Real nres;
/* Real last_h; */
if (ip == INULL)
error(E_NULL,"iter_gmres");
if ( ! ip->Ax || ! ip->b )
error(E_NULL,"iter_gmres");
if ( ! ip->stop_crit )
error(E_NULL,"iter_gmres");
if ( ip->k <= 0 )
error(E_BOUNDS,"iter_gmres");
if (ip->x != VNULL && ip->x->dim != ip->b->dim)
error(E_SIZES,"iter_gmres");
if (ip->eps <= 0.0) ip->eps = MACHEPS;
r = v_resize(r,ip->k+1);
u = v_resize(u,ip->b->dim);
rhs = v_resize(rhs,ip->k+1);
givs = v_resize(givs,ip->k); /* Givens rotations */
givc = v_resize(givc,ip->k);
MEM_STAT_REG(r,TYPE_VEC);
MEM_STAT_REG(u,TYPE_VEC);
MEM_STAT_REG(rhs,TYPE_VEC);
MEM_STAT_REG(givs,TYPE_VEC);
MEM_STAT_REG(givc,TYPE_VEC);
R = m_resize(R,ip->k+1,ip->k);
Q = m_resize(Q,ip->k,ip->b->dim);
MEM_STAT_REG(R,TYPE_MAT);
MEM_STAT_REG(Q,TYPE_MAT);
if (ip->x == VNULL) { /* ip->x == 0 */
ip->x = v_get(ip->b->dim);
ip->shared_x = FALSE;
}
v.dim = v.max_dim = ip->b->dim; /* v and v1 are pointers to rows */
v1.dim = v1.max_dim = ip->b->dim; /* of matrix Q */
if (ip->Bx != (Fun_Ax)NULL) { /* if precondition is defined */
z = v_resize(z,ip->b->dim);
MEM_STAT_REG(z,TYPE_VEC);
}
done = FALSE;
for (ip->steps = 0; ip->steps < ip->limit; ) {
/* restart */
ip->Ax(ip->A_par,ip->x,u); /* u = A*x */
v_sub(ip->b,u,u); /* u = b - A*x */
rr = u; /* rr is a pointer only */
if (ip->Bx) {
(ip->Bx)(ip->B_par,u,z); /* tmp = B*(b-A*x) */
rr = z;
}
nres = v_norm2(rr);
if (ip->steps == 0) {
if (ip->info) ip->info(ip,nres,VNULL,VNULL);
ip->init_res = nres;
}
if ( nres == 0.0 ) {
done = TRUE;
break;
}
v.ve = Q->me[0];
sv_mlt(1.0/nres,rr,&v);
v_zero(r);
v_zero(rhs);
rhs->ve[0] = nres;
for ( i = 0; i < ip->k && ip->steps < ip->limit; i++ ) {
ip->steps++;
v.ve = Q->me[i];
(ip->Ax)(ip->A_par,&v,u);
rr = u;
if (ip->Bx) {
(ip->Bx)(ip->B_par,u,z);
rr = z;
}
if (i < ip->k - 1) {
v1.ve = Q->me[i+1];
v_copy(rr,&v1);
for (j = 0; j <= i; j++) {
v.ve = Q->me[j];
/* r->ve[j] = in_prod(&v,rr); */
/* modified Gram-Schmidt algorithm */
r->ve[j] = in_prod(&v,&v1);
v_mltadd(&v1,&v,-r->ve[j],&v1);
}
r->ve[i+1] = nres = v_norm2(&v1);
if (nres <= MACHEPS*ip->init_res) {
for (j = 0; j < i; j++)
rot_vec(r,j,j+1,givc->ve[j],givs->ve[j],r);
set_col(R,i,r);
done = TRUE;
break;
}
sv_mlt(1.0/nres,&v1,&v1);
}
else { /* i == ip->k - 1 */
/* Q->me[ip->k] need not be computed */
for (j = 0; j <= i; j++) {
v.ve = Q->me[j];
r->ve[j] = in_prod(&v,rr);
}
nres = in_prod(rr,rr) - in_prod(r,r);
if (sqrt(fabs(nres)) <= MACHEPS*ip->init_res) {
for (j = 0; j < i; j++)
rot_vec(r,j,j+1,givc->ve[j],givs->ve[j],r);
set_col(R,i,r);
done = TRUE;
break;
}
if (nres < 0.0) { /* do restart */
i--;
ip->steps--;
break;
}
r->ve[i+1] = sqrt(nres);
}
/* QR update */
/* last_h = r->ve[i+1]; */ /* for test only */
for (j = 0; j < i; j++)
rot_vec(r,j,j+1,givc->ve[j],givs->ve[j],r);
givens(r->ve[i],r->ve[i+1],&givc->ve[i],&givs->ve[i]);
rot_vec(r,i,i+1,givc->ve[i],givs->ve[i],r);
rot_vec(rhs,i,i+1,givc->ve[i],givs->ve[i],rhs);
set_col(R,i,r);
nres = fabs((double) rhs->ve[i+1]);
if (ip->info) ip->info(ip,nres,VNULL,VNULL);
if ( ip->stop_crit(ip,nres,VNULL,VNULL) ) {
done = TRUE;
break;
}
}
/* use ixi submatrix of R */
if (i >= ip->k) i = ip->k - 1;
R = m_resize(R,i+1,i+1);
rhs = v_resize(rhs,i+1);
/* test only */
/* test_gmres(ip,i,Q,R,givc,givs,last_h); */
Usolve(R,rhs,rhs,0.0); /* solve a system: R*x = rhs */
/* new approximation */
for (j = 0; j <= i; j++) {
v.ve = Q->me[j];
v_mltadd(ip->x,&v,rhs->ve[j],ip->x);
}
if (done) break;
/* back to old dimensions */
rhs = v_resize(rhs,ip->k+1);
R = m_resize(R,ip->k+1,ip->k);
}
#ifdef THREADSAFE
V_FREE(u); V_FREE(r); V_FREE(rhs);
V_FREE(givs); V_FREE(givc); V_FREE(z);
M_FREE(Q); M_FREE(R);
#endif
return ip->x;
}
/* iter_spgmres - a simple interface to iter_gmres */
#ifndef ANSI_C
VEC *iter_spgmres(A,B,b,tol,x,k,limit,steps)
SPMAT *A, *B;
VEC *b, *x;
double tol;
int *steps,k,limit;
#else
VEC *iter_spgmres(SPMAT *A, SPMAT *B, VEC *b, double tol,
VEC *x, int k, int limit, int *steps)
#endif
{
ITER *ip;
ip = iter_get(0,0);
ip->Ax = (Fun_Ax) sp_mv_mlt;
ip->A_par = (void *) A;
if (B) {
ip->Bx = (Fun_Ax) sp_mv_mlt;
ip->B_par = (void *) B;
}
else {
ip->Bx = (Fun_Ax) NULL;
ip->B_par = NULL;
}
ip->k = k;
ip->limit = limit;
ip->info = (Fun_info) NULL;
ip->b = b;
ip->eps = tol;
ip->x = x;
iter_gmres(ip);
x = ip->x;
if (steps) *steps = ip->steps;
ip->shared_x = ip->shared_b = TRUE;
iter_free(ip); /* release only ITER structure */
return x;
}
/* for testing mgcr */
#ifndef ANSI_C
static void test_mgcr(ip,i,Q,R)
ITER *ip;
int i;
MAT *Q, *R;
#else
static void test_mgcr(ITER *ip, int i, MAT *Q, MAT *R)
#endif
{
VEC vt, vt1;
static MAT *R1=MNULL;
static VEC *r=VNULL, *r1=VNULL;
VEC *rr;
int k,j;
Real sm;
/* check Q*Q^T = I */
vt.dim = vt.max_dim = ip->b->dim;
vt1.dim = vt1.max_dim = ip->b->dim;
Q = m_resize(Q,i+1,ip->b->dim);
R1 = m_resize(R1,i+1,i+1);
r = v_resize(r,ip->b->dim);
r1 = v_resize(r1,ip->b->dim);
MEM_STAT_REG(R1,TYPE_MAT);
MEM_STAT_REG(r,TYPE_VEC);
MEM_STAT_REG(r1,TYPE_VEC);
m_zero(R1);
for (k=1; k <= i; k++)
for (j=1; j <= i; j++) {
vt.ve = Q->me[k];
vt1.ve = Q->me[j];
R1->me[k][j] = in_prod(&vt,&vt1);
}
for (j=1; j <= i; j++)
R1->me[j][j] -= 1.0;
#ifndef MEX
if (m_norm_inf(R1) > MACHEPS*ip->b->dim)
printf(" ! (mgcr:) m_norm_inf(Q*Q^T) = %g\n",m_norm_inf(R1));
#endif
/* check (r_i,Ap_j) = 0 for j <= i */
ip->Ax(ip->A_par,ip->x,r);
v_sub(ip->b,r,r);
rr = r;
if (ip->Bx) {
ip->Bx(ip->B_par,r,r1);
rr = r1;
}
#ifndef MEX
printf(" ||r|| = %g\n",v_norm2(rr));
#endif
sm = 0.0;
for (j = 1; j <= i; j++) {
vt.ve = Q->me[j];
sm = max(sm,in_prod(&vt,rr));
}
#ifndef MEX
if (sm >= MACHEPS*ip->b->dim)
printf(" ! (mgcr:) max_j (r,Ap_j) = %g\n",sm);
#endif
}
/*
iter_mgcr -- modified generalized conjugate residual algorithm;
fast version of GCR;
*/
#ifndef ANSI_C
VEC *iter_mgcr(ip)
ITER *ip;
#else
VEC *iter_mgcr(ITER *ip)
#endif
{
STATIC VEC *As=VNULL, *beta=VNULL, *alpha=VNULL, *z=VNULL;
STATIC MAT *N=MNULL, *H=MNULL;
VEC *rr, v, s; /* additional pointer and structures */
Real nres; /* norm of a residual */
Real dd; /* coefficient d_i */
int i,j;
int done; /* if TRUE then stop the iterative process */
int dim; /* dimension of the problem */
/* ip cannot be NULL */
if (ip == INULL) error(E_NULL,"mgcr");
/* Ax, b and stopping criterion must be given */
if (! ip->Ax || ! ip->b || ! ip->stop_crit)
error(E_NULL,"mgcr");
/* at least one direction vector must exist */
if ( ip->k <= 0) error(E_BOUNDS,"mgcr");
/* if the vector x is given then b and x must have the same dimension */
if ( ip->x && ip->x->dim != ip->b->dim)
error(E_SIZES,"mgcr");
if (ip->eps <= 0.0) ip->eps = MACHEPS;
dim = ip->b->dim;