VEC *QRsolve(const MAT *QR, const VEC *diag, const VEC *b, VEC *x)
#endif
{
int limit;
STATIC VEC *tmp = VNULL;
if ( ! QR || ! diag || ! b )
error(E_NULL,"QRsolve");
limit = min(QR->m,QR->n);
if ( diag->dim < limit || b->dim != QR->m )
error(E_SIZES,"QRsolve");
tmp = v_resize(tmp,limit);
MEM_STAT_REG(tmp,TYPE_VEC);
x = v_resize(x,QR->n);
_Qsolve(QR,diag,b,x,tmp);
x = Usolve(QR,x,x,0.0);
v_resize(x,QR->n);
#ifdef THREADSAFE
V_FREE(tmp);
#endif
return x;
}
int
LUsolve(Matrix A, int *indexarray, Vector b, Vector x)
{
int i, dim = A->dim;
for (i = 0; i < dim; i++)
x->ve[i] = b->ve[indexarray[i]];
if (Lsolve(A, x, x, 1.) == -1 || Usolve(A, x, x, 0.) == -1)
return -1;
return 0;
}
VEC *LUsolve(const MAT *LU, PERM *pivot, const VEC *b, VEC *x)
#endif
{
if ( ! LU || ! b || ! pivot )
error(E_NULL,"LUsolve");
if ( LU->m != LU->n || LU->n != b->dim )
error(E_SIZES,"LUsolve");
x = v_resize(x,b->dim);
px_vec(pivot,b,x); /* x := P.b */
Lsolve(LU,x,x,1.0); /* implicit diagonal = 1 */
Usolve(LU,x,x,0.0); /* explicit diagonal */
return (x);
}
/************************************
Given the factorization LB = U for some B, solve the problem
Bx = vec for x
Solve using LUMOD functions.
************************************/
void LU_Solve0(PT_Matrix pL, PT_Matrix pU, double *vec, double *x)
{
int mode;
ptrdiff_t n;
n = Matrix_Rows(pL);
/* solve using lumod */
/* solve for Bx = vec */
mode = 1;
/* due to 1-based indexing in Lprod, Usolve we need to shift vectors backwards */
/* Computes x = L*vec */
Lprod(mode, pL->rows_alloc, n, pL->A-1, vec-1, x-1);
/* Computes x_new s.t. U x_new = x */
Usolve(mode, pU->rows_alloc, n, pU->A-1, x-1);
/* Vector_Print_raw(x,n); */
}
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;
As = v_resize(As,dim);
alpha = v_resize(alpha,ip->k);
beta = v_resize(beta,ip->k);
MEM_STAT_REG(As,TYPE_VEC);
MEM_STAT_REG(alpha,TYPE_VEC);
MEM_STAT_REG(beta,TYPE_VEC);
H = m_resize(H,ip->k,ip->k);
N = m_resize(N,ip->k,dim);
MEM_STAT_REG(H,TYPE_MAT);
MEM_STAT_REG(N,TYPE_MAT);
/* if a preconditioner is defined */
if (ip->Bx) {
z = v_resize(z,dim);
MEM_STAT_REG(z,TYPE_VEC);
}
/* if x is NULL then it is assumed that x has
entries with value zero */
if ( ! ip->x ) {
ip->x = v_get(ip->b->dim);
ip->shared_x = FALSE;
}
/* v and s are additional pointers to rows of N */
/* they must have the same dimension as rows of N */
v.dim = v.max_dim = s.dim = s.max_dim = dim;
done = FALSE;
for (ip->steps = 0; ip->steps < ip->limit; ) {
(*ip->Ax)(ip->A_par,ip->x,As); /* As = A*x */
v_sub(ip->b,As,As); /* As = b - A*x */
rr = As; /* rr is an additional pointer */
/* if a preconditioner is defined */
if (ip->Bx) {
(*ip->Bx)(ip->B_par,As,z); /* z = B*(b-A*x) */
rr = z;
}
/* norm of the residual */
nres = v_norm2(rr);
dd = nres; /* dd = ||r_i|| */
/* check if the norm of the residual is zero */
if (ip->steps == 0) {
/* information for a user */
if (ip->info) (*ip->info)(ip,nres,As,rr);
ip->init_res = fabs(nres);
}
if (nres == 0.0) {
/* iterative process is finished */
done = TRUE;
break;
}
/* save this residual in the first row of N */
v.ve = N->me[0];
v_copy(rr,&v);
for (i = 0; i < ip->k && ip->steps < ip->limit; i++) {
ip->steps++;
v.ve = N->me[i]; /* pointer to a row of N (=s_i) */
/* note that we must use here &v, not v */
(*ip->Ax)(ip->A_par,&v,As);
rr = As; /* As = A*s_i */
if (ip->Bx) {
(*ip->Bx)(ip->B_par,As,z); /* z = B*A*s_i */
rr = z;
}
if (i < ip->k - 1) {
s.ve = N->me[i+1]; /* pointer to a row of N (=s_{i+1}) */
v_copy(rr,&s); /* s_{i+1} = B*A*s_i */
for (j = 0; j <= i-1; j++) {
v.ve = N->me[j+1]; /* pointer to a row of N (=s_{j+1}) */
/* beta->ve[j] = in_prod(&v,rr); */ /* beta_{j,i} */
/* modified Gram-Schmidt algorithm */
beta->ve[j] = in_prod(&v,&s); /* beta_{j,i} */
/* s_{i+1} -= beta_{j,i}*s_{j+1} */
v_mltadd(&s,&v,- beta->ve[j],&s);
}
/* beta_{i,i} = ||s_{i+1}||_2 */
beta->ve[i] = nres = v_norm2(&s);
if ( nres <= MACHEPS*ip->init_res) {
/* s_{i+1} == 0 */
i--;
done = TRUE;
break;
}
sv_mlt(1.0/nres,&s,&s); /* normalize s_{i+1} */
v.ve = N->me[0];
alpha->ve[i] = in_prod(&v,&s); /* alpha_i = (s_0 , s_{i+1}) */
}
else {
for (j = 0; j <= i-1; j++) {
v.ve = N->me[j+1]; /* pointer to a row of N (=s_{j+1}) */
beta->ve[j] = in_prod(&v,rr); /* beta_{j,i} */
}
nres = in_prod(rr,rr); /* rr = B*A*s_{k-1} */
for (j = 0; j <= i-1; j++)
nres -= beta->ve[j]*beta->ve[j];
if (sqrt(fabs(nres)) <= MACHEPS*ip->init_res) {
/* s_k is zero */
i--;
done = TRUE;
break;
}
if (nres < 0.0) { /* do restart */
i--;
ip->steps--;
break;
}
beta->ve[i] = sqrt(nres); /* beta_{k-1,k-1} */
v.ve = N->me[0];
alpha->ve[i] = in_prod(&v,rr);
for (j = 0; j <= i-1; j++)
alpha->ve[i] -= beta->ve[j]*alpha->ve[j];
alpha->ve[i] /= beta->ve[i]; /* alpha_{k-1} */
}
set_col(H,i,beta);
/* other method of computing dd */
/* if (fabs((double)alpha->ve[i]) > dd) {
nres = - dd*dd + alpha->ve[i]*alpha->ve[i];
nres = sqrt((double) nres);
if (ip->info) (*ip->info)(ip,-nres,VNULL,VNULL);
break;
} */
/* to avoid overflow/underflow in computing dd */
/* dd *= cos(asin((double)(alpha->ve[i]/dd))); */
nres = alpha->ve[i]/dd;
if (fabs(nres-1.0) <= MACHEPS*ip->init_res)
dd = 0.0;
else {
nres = 1.0 - nres*nres;
if (nres < 0.0) {
nres = sqrt((double) -nres);
if (ip->info) (*ip->info)(ip,-dd*nres,VNULL,VNULL);
break;
}
dd *= sqrt((double) nres);
}
if (ip->info) (*ip->info)(ip,dd,VNULL,VNULL);
if ( ip->stop_crit(ip,dd,VNULL,VNULL) ) {
/* stopping criterion is satisfied */
done = TRUE;
break;
}
} /* end of for */
if (i >= ip->k) i = ip->k - 1;
/* use (i+1) by (i+1) submatrix of H */
H = m_resize(H,i+1,i+1);
alpha = v_resize(alpha,i+1);
Usolve(H,alpha,alpha,0.0); /* c_i is saved in alpha */
for (j = 0; j <= i; j++) {
v.ve = N->me[j];
v_mltadd(ip->x,&v,alpha->ve[j],ip->x);
}
if (done) break; /* stop the iterative process */
alpha = v_resize(alpha,ip->k);
H = m_resize(H,ip->k,ip->k);
} /* end of while */
#ifdef THREADSAFE
V_FREE(As);
V_FREE(beta);
V_FREE(alpha);
V_FREE(z);
M_FREE(N);
M_FREE(H);
#endif
return ip->x; /* return the solution */
}
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;
}
double QRcondest(const MAT *QR)
#endif
{
STATIC VEC *y=VNULL;
Real norm1, norm2, sum, tmp1, tmp2;
int i, j, limit;
if ( QR == MNULL )
error(E_NULL,"QRcondest");
limit = min(QR->m,QR->n);
for ( i = 0; i < limit; i++ )
if ( QR->me[i][i] == 0.0 )
return HUGE_VAL;
y = v_resize(y,limit);
MEM_STAT_REG(y,TYPE_VEC);
/* use the trick for getting a unit vector y with ||R.y||_inf small
from the LU condition estimator */
for ( i = 0; i < limit; i++ )
{
sum = 0.0;
for ( j = 0; j < i; j++ )
sum -= QR->me[j][i]*y->ve[j];
sum -= (sum < 0.0) ? 1.0 : -1.0;
y->ve[i] = sum / QR->me[i][i];
}
UTmlt(QR,y,y);
/* now apply inverse power method to R^T.R */
for ( i = 0; i < 3; i++ )
{
tmp1 = v_norm2(y);
sv_mlt(1/tmp1,y,y);
UTsolve(QR,y,y,0.0);
tmp2 = v_norm2(y);
sv_mlt(1/v_norm2(y),y,y);
Usolve(QR,y,y,0.0);
}
/* now compute approximation for ||R^{-1}||_2 */
norm1 = sqrt(tmp1)*sqrt(tmp2);
/* now use complementary approach to compute approximation to ||R||_2 */
for ( i = limit-1; i >= 0; i-- )
{
sum = 0.0;
for ( j = i+1; j < limit; j++ )
sum += QR->me[i][j]*y->ve[j];
y->ve[i] = (sum >= 0.0) ? 1.0 : -1.0;
y->ve[i] = (QR->me[i][i] >= 0.0) ? y->ve[i] : - y->ve[i];
}
/* now apply power method to R^T.R */
for ( i = 0; i < 3; i++ )
{
tmp1 = v_norm2(y);
sv_mlt(1/tmp1,y,y);
Umlt(QR,y,y);
tmp2 = v_norm2(y);
sv_mlt(1/tmp2,y,y);
UTmlt(QR,y,y);
}
norm2 = sqrt(tmp1)*sqrt(tmp2);
/* printf("QRcondest: norm1 = %g, norm2 = %g\n",norm1,norm2); */
#ifdef THREADSAFE
V_FREE(y);
#endif
return norm1*norm2;
}
