cs_transpose.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' */
cs *cs_transpose (const cs *A, CS_INT values)
{
    CS_INT p, q, j, *Cp, *Ci, n, m, *Ap, *Ai, *w ;
    CS_ENTRY *Cx, *Ax ;
    cs *C ;
    if (!CS_CSC (A)) return (NULL) ;    /* check inputs */
    m = A->m ; n = A->n ; Ap = A->p ; Ai = A->i ; Ax = A->x ;
    C = cs_spalloc (n, m, Ap [n], values && Ax, 0) ;       /* allocate result */
    w = cs_calloc (m, 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 (p = 0 ; p < Ap [n] ; p++) w [Ai [p]]++ ;          /* row counts */
    cs_cumsum (Cp, w, m) ;                                 /* row pointers */
    for (j = 0 ; j < n ; j++)
    {
        for (p = Ap [j] ; p < Ap [j+1] ; p++)
        {
            Ci [q = w [Ai [p]]++] = j ; /* place A(i,j) as entry C(j,i) */
            if (Cx) Cx [q] = (values > 0) ? CS_CONJ (Ax [p]) : Ax [p] ;
        }
    }
    return (cs_done (C, w, NULL, 1)) ;  /* success; free w and return C */
}