40 lines
1.5 KiB
C
40 lines
1.5 KiB
C
#include "cs.h"
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/* C = A(p,p) where A and C are symmetric the upper part stored; pinv not p */
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cs *cs_symperm (const cs *A, const int *pinv, int values)
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{
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int i, j, p, q, i2, j2, n, *Ap, *Ai, *Cp, *Ci, *w ;
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double *Cx, *Ax ;
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cs *C ;
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if (!CS_CSC (A)) return (NULL) ; /* check inputs */
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n = A->n ; Ap = A->p ; Ai = A->i ; Ax = A->x ;
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C = cs_spalloc (n, n, Ap [n], values && (Ax != NULL), 0) ; /* alloc result*/
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w = cs_calloc (n, sizeof (int)) ; /* get workspace */
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if (!C || !w) return (cs_done (C, w, NULL, 0)) ; /* out of memory */
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Cp = C->p ; Ci = C->i ; Cx = C->x ;
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for (j = 0 ; j < n ; j++) /* count entries in each column of C */
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{
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j2 = pinv ? pinv [j] : j ; /* column j of A is column j2 of C */
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for (p = Ap [j] ; p < Ap [j+1] ; p++)
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{
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i = Ai [p] ;
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if (i > j) continue ; /* skip lower triangular part of A */
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i2 = pinv ? pinv [i] : i ; /* row i of A is row i2 of C */
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w [CS_MAX (i2, j2)]++ ; /* column count of C */
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}
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}
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cs_cumsum (Cp, w, n) ; /* compute column pointers of C */
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for (j = 0 ; j < n ; j++)
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{
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j2 = pinv ? pinv [j] : j ; /* column j of A is column j2 of C */
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for (p = Ap [j] ; p < Ap [j+1] ; p++)
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{
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i = Ai [p] ;
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if (i > j) continue ; /* skip lower triangular part of A*/
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i2 = pinv ? pinv [i] : i ; /* row i of A is row i2 of C */
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Ci [q = w [CS_MAX (i2, j2)]++] = CS_MIN (i2, j2) ;
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if (Cx) Cx [q] = Ax [p] ;
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}
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}
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return (cs_done (C, w, NULL, 1)) ; /* success; free workspace, return C */
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}
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