cs_compress.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 = compressed-column form of a triplet matrix T */
cs *cs_compress (const cs *T)
{
    CS_INT m, n, nz, p, k, *Cp, *Ci, *w, *Ti, *Tj ;
    CS_ENTRY *Cx, *Tx ;
    cs *C ;
    if (!CS_TRIPLET (T)) return (NULL) ;                /* check inputs */
    m = T->m ; n = T->n ; Ti = T->i ; Tj = T->p ; Tx = T->x ; nz = T->nz ;
    C = cs_spalloc (m, n, nz, Tx != NULL, 0) ;          /* allocate result */
    w = cs_calloc (n, sizeof (CS_INT)) ;                   /* get workspace */
    if (!C || !w) return (cs_done (C, w, NULL, 0)) ;    /* out of memory */
    Cp = C->p ; Ci = C->i ; Cx = C->x ;
    for (k = 0 ; k < nz ; k++) w [Tj [k]]++ ;           /* column counts */
    cs_cumsum (Cp, w, n) ;                              /* column pointers */
    for (k = 0 ; k < nz ; k++)
    {
        Ci [p = w [Tj [k]]++] = Ti [k] ;    /* A(i,j) is the pth entry in C */
        if (Cx) Cx [p] = Tx [k] ;
    }
    return (cs_done (C, w, NULL, 1)) ;      /* success; free w and return C */
}