cs_permute.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(p,q) where p and q are permutations of 0..m-1 and 0..n-1. */
cs *cs_permute (const cs *A, const CS_INT *pinv, const CS_INT *q, CS_INT values)
{
    CS_INT t, j, k, nz = 0, m, n, *Ap, *Ai, *Cp, *Ci ;
    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 (m, n, Ap [n], values && Ax != NULL, 0) ;  /* alloc result */
    if (!C) return (cs_done (C, NULL, NULL, 0)) ;   /* out of memory */
    Cp = C->p ; Ci = C->i ; Cx = C->x ;
    for (k = 0 ; k < n ; k++)
    {
        Cp [k] = nz ;                   /* column k of C is column q[k] of A */
        j = q ? (q [k]) : k ;
        for (t = Ap [j] ; t < Ap [j+1] ; t++)
        {
            if (Cx) Cx [nz] = Ax [t] ;  /* row i of A is row pinv[i] of C */
            Ci [nz++] = pinv ? (pinv [Ai [t]]) : Ai [t] ;
        }
    }
    Cp [n] = nz ;                       /* finalize the last column of C */
    return (cs_done (C, NULL, NULL, 1)) ;
}