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OS/2 Shareware BBS: 22 gnu
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mesch12a.zip
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splufctr.c
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1994-01-13
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/**************************************************************************
**
** Copyright (C) 1993 David E. Steward & 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.
**
***************************************************************************/
/*
Sparse LU factorisation -- NO pivoting
See also: sparse.[ch] etc for details about sparse matrices
*/
#include <stdio.h>
#include <math.h>
#include "sparse2.h"
/* Macro for speedup */
/* #define sprow_idx2(r,c,hint) \
( ( (hint) >= 0 && (r)->elt[hint].col == (c)) ? hint : sprow_idx((r),(c)) ) */
/* spLUfactor -- sparse LU factorisation with pivoting
-- uses partial pivoting and Markowitz criterion
|a[p][k]| >= alpha * max_i |a[i][k]|
-- creates fill-in as needed
-- in situ factorisation */
SPMAT *spLUfactor(A,px,alpha)
SPMAT *A;
PERM *px;
double alpha;
{
int i, best_i, k, idx, len, best_len, m, n;
SPROW *r, *r_piv, tmp_row;
static SPROW *merge = (SPROW *)NULL;
Real max_val, tmp;
static VEC *col_vals=VNULL;
if ( ! A || ! px )
error(E_NULL,"spLUfctr");
if ( alpha <= 0.0 || alpha > 1.0 )
error(E_RANGE,"alpha in spLUfctr");
if ( px->size <= A->m )
px = px_resize(px,A->m);
px_ident(px);
col_vals = v_resize(col_vals,A->m);
MEM_STAT_REG(col_vals,TYPE_VEC);
m = A->m; n = A->n;
if ( ! A->flag_col )
sp_col_access(A);
if ( ! A->flag_diag )
sp_diag_access(A);
A->flag_col = A->flag_diag = FALSE;
if ( ! merge ) {
merge = sprow_get(20);
MEM_STAT_REG(merge,TYPE_SPROW);
}
for ( k = 0; k < n; k++ )
{
/* find pivot row/element for partial pivoting */
/* get first row with a non-zero entry in the k-th column */
max_val = 0.0;
for ( i = k; i < m; i++ )
{
r = &(A->row[i]);
idx = sprow_idx(r,k);
if ( idx < 0 )
tmp = 0.0;
else
tmp = r->elt[idx].val;
if ( fabs(tmp) > max_val )
max_val = fabs(tmp);
col_vals->ve[i] = tmp;
}
if ( max_val == 0.0 )
continue;
best_len = n+1; /* only if no possibilities */
best_i = -1;
for ( i = k; i < m; i++ )
{
tmp = fabs(col_vals->ve[i]);
if ( tmp == 0.0 )
continue;
if ( tmp >= alpha*max_val )
{
r = &(A->row[i]);
idx = sprow_idx(r,k);
len = (r->len) - idx;
if ( len < best_len )
{
best_len = len;
best_i = i;
}
}
}
/* swap row #best_i with row #k */
MEM_COPY(&(A->row[best_i]),&tmp_row,sizeof(SPROW));
MEM_COPY(&(A->row[k]),&(A->row[best_i]),sizeof(SPROW));
MEM_COPY(&tmp_row,&(A->row[k]),sizeof(SPROW));
/* swap col_vals entries */
tmp = col_vals->ve[best_i];
col_vals->ve[best_i] = col_vals->ve[k];
col_vals->ve[k] = tmp;
px_transp(px,k,best_i);
r_piv = &(A->row[k]);
for ( i = k+1; i < n; i++ )
{
/* compute and set multiplier */
tmp = col_vals->ve[i]/col_vals->ve[k];
if ( tmp != 0.0 )
sp_set_val(A,i,k,tmp);
else
continue;
/* perform row operations */
merge->len = 0;
r = &(A->row[i]);
sprow_mltadd(r,r_piv,-tmp,k+1,merge,TYPE_SPROW);
idx = sprow_idx(r,k+1);
if ( idx < 0 )
idx = -(idx+2);
/* see if r needs expanding */
if ( r->maxlen < idx + merge->len )
sprow_xpd(r,idx+merge->len,TYPE_SPMAT);
r->len = idx+merge->len;
MEM_COPY((char *)(merge->elt),(char *)&(r->elt[idx]),
merge->len*sizeof(row_elt));
}
}
return A;
}
/* spLUsolve -- solve A.x = b using factored matrix A from spLUfactor()
-- returns x
-- may not be in-situ */
VEC *spLUsolve(A,pivot,b,x)
SPMAT *A;
PERM *pivot;
VEC *b, *x;
{
int i, idx, len, lim;
Real sum, *x_ve;
SPROW *r;
row_elt *elt;
if ( ! A || ! b )
error(E_NULL,"spLUsolve");
if ( (pivot != PNULL && A->m != pivot->size) || A->m != b->dim )
error(E_SIZES,"spLUsolve");
if ( ! x || x->dim != A->n )
x = v_resize(x,A->n);
if ( pivot != PNULL )
x = px_vec(pivot,b,x);
else
x = v_copy(b,x);
x_ve = x->ve;
lim = min(A->m,A->n);
for ( i = 0; i < lim; i++ )
{
sum = x_ve[i];
r = &(A->row[i]);
len = r->len;
elt = r->elt;
for ( idx = 0; idx < len && elt->col < i; idx++, elt++ )
sum -= elt->val*x_ve[elt->col];
x_ve[i] = sum;
}
for ( i = lim-1; i >= 0; i-- )
{
sum = x_ve[i];
r = &(A->row[i]);
len = r->len;
elt = &(r->elt[len-1]);
for ( idx = len-1; idx >= 0 && elt->col > i; idx--, elt-- )
sum -= elt->val*x_ve[elt->col];
if ( idx < 0 || elt->col != i || elt->val == 0.0 )
error(E_SING,"spLUsolve");
x_ve[i] = sum/elt->val;
}
return x;
}
/* spLUTsolve -- solve A.x = b using factored matrix A from spLUfactor()
-- returns x
-- may not be in-situ */
VEC *spLUTsolve(A,pivot,b,x)
SPMAT *A;
PERM *pivot;
VEC *b, *x;
{
int i, idx, lim, rownum;
Real sum, *tmp_ve;
/* SPROW *r; */
row_elt *elt;
static VEC *tmp=VNULL;
if ( ! A || ! b )
error(E_NULL,"spLUTsolve");
if ( (pivot != PNULL && A->m != pivot->size) || A->m != b->dim )
error(E_SIZES,"spLUTsolve");
tmp = v_copy(b,tmp);
MEM_STAT_REG(tmp,TYPE_VEC);
if ( ! A->flag_col )
sp_col_access(A);
if ( ! A->flag_diag )
sp_diag_access(A);
lim = min(A->m,A->n);
tmp_ve = tmp->ve;
/* solve U^T.tmp = b */
for ( i = 0; i < lim; i++ )
{
sum = tmp_ve[i];
rownum = A->start_row[i];
idx = A->start_idx[i];
if ( rownum < 0 || idx < 0 )
error(E_SING,"spLUTsolve");
while ( rownum < i && rownum >= 0 && idx >= 0 )
{
elt = &(A->row[rownum].elt[idx]);
sum -= elt->val*tmp_ve[rownum];
rownum = elt->nxt_row;
idx = elt->nxt_idx;
}
if ( rownum != i )
error(E_SING,"spLUTsolve");
elt = &(A->row[rownum].elt[idx]);
if ( elt->val == 0.0 )
error(E_SING,"spLUTsolve");
tmp_ve[i] = sum/elt->val;
}
/* now solve L^T.tmp = (old) tmp */
for ( i = lim-1; i >= 0; i-- )
{
sum = tmp_ve[i];
rownum = i;
idx = A->row[rownum].diag;
if ( idx < 0 )
error(E_NULL,"spLUTsolve");
elt = &(A->row[rownum].elt[idx]);
rownum = elt->nxt_row;
idx = elt->nxt_idx;
while ( rownum < lim && rownum >= 0 && idx >= 0 )
{
elt = &(A->row[rownum].elt[idx]);
sum -= elt->val*tmp_ve[rownum];
rownum = elt->nxt_row;
idx = elt->nxt_idx;
}
tmp_ve[i] = sum;
}
if ( pivot != PNULL )
x = pxinv_vec(pivot,tmp,x);
else
x = v_copy(tmp,x);
return x;
}
/* spILUfactor -- sparse modified incomplete LU factorisation with
no pivoting
-- all pivot entries are ensured to be >= alpha in magnitude
-- setting alpha = 0 gives incomplete LU factorisation
-- no fill-in is generated
-- in situ factorisation */
SPMAT *spILUfactor(A,alpha)
SPMAT *A;
double alpha;
{
int i, k, idx, idx_piv, m, n;
SPROW *r, *r_piv;
Real piv_val, tmp;
/* printf("spILUfactor: entered\n"); */
if ( ! A )
error(E_NULL,"spILUfactor");
if ( alpha < 0.0 )
error(E_RANGE,"[alpha] in spILUfactor");
m = A->m; n = A->n;
if ( ! A->flag_diag )
sp_diag_access(A);
for ( k = 0; k < n; k++ )
{
/* printf("spILUfactor: checkpoint A: k = %d\n",k); */
r_piv = &(A->row[k]);
idx_piv = r_piv->diag;
if ( idx_piv < 0 )
{
sprow_set_val(r_piv,k,alpha);
idx_piv = sprow_idx(r_piv,k);
}
/* printf("spILUfactor: checkpoint B\n"); */
if ( idx_piv < 0 )
error(E_BOUNDS,"spILUfactor");
piv_val = r_piv->elt[idx_piv].val;
/* printf("spILUfactor: checkpoint C\n"); */
if ( fabs(piv_val) < alpha )
piv_val = ( piv_val < 0.0 ) ? -alpha : alpha;
if ( piv_val == 0.0 ) /* alpha == 0.0 too! */
error(E_SING,"spILUfactor");
for ( i = k+1; i < n; i++ )
{
/* printf("spILUfactor: checkpoint D: i = %d\n",i); */
/* perform row operations */
r = &(A->row[i]);
idx = sprow_idx(r,k);
if ( idx < 0 )
continue;
/* printf("spILUfactor: checkpoint E\n"); */
/* compute and set multiplier */
r->elt[idx].val = tmp = r->elt[idx].val/piv_val;
/* printf("spILUfactor: piv_val = %g, multiplier = %g\n",
piv_val, tmp); */
if ( tmp == 0.0 )
continue;
idx = sprow_idx(r,k+1);
if ( idx < 0 )
idx = -(idx+2);
/* printf("spILUfactor: checkpoint F: idx = %d, idx_piv = %d\n",
idx, idx_piv); */
while ( idx_piv < r_piv->len && idx < r->len )
{
/* printf("spILUfactor: checkpoint G: idx = %d, idx_piv = %d\n",
idx, idx_piv); */
if ( r_piv->elt[idx_piv].col < r->elt[idx].col )
idx_piv++;
else if ( r_piv->elt[idx_piv].col > r->elt[idx].col )
idx++;
else /* column numbers match */
{
r->elt[idx].val -= tmp*r_piv->elt[idx_piv].val;
idx++; idx_piv++;
}
}
}
}
/* printf("spILUfactor: exiting\n"); */
return A;
}