cs_multiply.c

/*
 * CXSPARSE: a Concise Sparse Matrix package - Extended.
 * Copyright (c) 2006-2009, Timothy A. Davis.
 * http://www.cise.ufl.edu/research/sparse/CXSparse
 * 
 * CXSparse is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * CXSparse is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this Module; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "cs.h"
/* C = A*B */
cs *cs_multiply (const cs *A, const cs *B)
{
    CS_INT p, j, nz = 0, anz, *Cp, *Ci, *Bp, m, n, bnz, *w, values, *Bi ;
    CS_ENTRY *x, *Bx, *Cx ;
    cs *C ;
    if (!CS_CSC (A) || !CS_CSC (B)) return (NULL) ;      /* check inputs */
    if (A->n != B->m) return (NULL) ;
    m = A->m ; anz = A->p [A->n] ;
    n = B->n ; Bp = B->p ; Bi = B->i ; Bx = B->x ; bnz = Bp [n] ;
    w = cs_calloc (m, sizeof (CS_INT)) ;                    /* get workspace */
    values = (A->x != NULL) && (Bx != NULL) ;
    x = values ? cs_malloc (m, sizeof (CS_ENTRY)) : NULL ; /* get workspace */
    C = cs_spalloc (m, n, anz + bnz, values, 0) ;        /* allocate result */
    if (!C || !w || (values && !x)) return (cs_done (C, w, x, 0)) ;
    Cp = C->p ;
    for (j = 0 ; j < n ; j++)
    {
        if (nz + m > C->nzmax && !cs_sprealloc (C, 2*(C->nzmax)+m))
        {
            return (cs_done (C, w, x, 0)) ;             /* out of memory */
        } 
        Ci = C->i ; Cx = C->x ;         /* C->i and C->x may be reallocated */
        Cp [j] = nz ;                   /* column j of C starts here */
        for (p = Bp [j] ; p < Bp [j+1] ; p++)
        {
            nz = cs_scatter (A, Bi [p], Bx ? Bx [p] : 1, w, x, j+1, C, nz) ;
        }
        if (values) for (p = Cp [j] ; p < nz ; p++) Cx [p] = x [Ci [p]] ;
    }
    Cp [n] = nz ;                       /* finalize the last column of C */
    cs_sprealloc (C, 0) ;               /* remove extra space from C */
    return (cs_done (C, w, x, 1)) ;     /* success; free workspace, return C */
}