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#include "cs.h"
/* ordering and symbolic analysis for a Cholesky factorization */
css *cs_schol (int order, const cs *A)
{
int n, *c, *post, *P ;
cs *C ;
css *S ;
if (!CS_CSC (A)) return (NULL) ; /* check inputs */
n = A->n ;
S = cs_calloc (1, sizeof (css)) ; /* allocate result S */
if (!S) return (NULL) ; /* out of memory */
P = cs_amd (order, A) ; /* P = amd(A+A'), or natural */
S->pinv = cs_pinv (P, n) ; /* find inverse permutation */
cs_free (P) ;
if (order && !S->pinv) return (cs_sfree (S)) ;
C = cs_symperm (A, S->pinv, 0) ; /* C = spones(triu(A(P,P))) */
S->parent = cs_etree (C, 0) ; /* find etree of C */
post = cs_post (S->parent, n) ; /* postorder the etree */
c = cs_counts (C, S->parent, post, 0) ; /* find column counts of chol(C) */
cs_free (post) ;
cs_spfree (C) ;
S->cp = cs_malloc (n+1, sizeof (int)) ; /* allocate result S->cp */
S->unz = S->lnz = cs_cumsum (S->cp, c, n) ; /* find column pointers for L */
cs_free (c) ;
return ((S->lnz >= 0) ? S : cs_sfree (S)) ;
}
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