1 #include "cs.h"
2 /* find nonzero pattern of Cholesky L(k,1:k-1) using etree and triu(A(:,k)) */
cs_ereach(const cs * A,CS_INT k,const CS_INT * parent,CS_INT * s,CS_INT * w)3 CS_INT cs_ereach (const cs *A, CS_INT k, const CS_INT *parent, CS_INT *s, CS_INT *w)
4 {
5 CS_INT i, p, n, len, top, *Ap, *Ai ;
6 if (!CS_CSC (A) || !parent || !s || !w) return (-1) ; /* check inputs */
7 top = n = A->n ; Ap = A->p ; Ai = A->i ;
8 CS_MARK (w, k) ; /* mark node k as visited */
9 for (p = Ap [k] ; p < Ap [k+1] ; p++)
10 {
11 i = Ai [p] ; /* A(i,k) is nonzero */
12 if (i > k) continue ; /* only use upper triangular part of A */
13 for (len = 0 ; !CS_MARKED (w,i) ; i = parent [i]) /* traverse up etree*/
14 {
15 s [len++] = i ; /* L(k,i) is nonzero */
16 CS_MARK (w, i) ; /* mark i as visited */
17 }
18 while (len > 0) s [--top] = s [--len] ; /* push path onto stack */
19 }
20 for (p = top ; p < n ; p++) CS_MARK (w, s [p]) ; /* unmark all nodes */
21 CS_MARK (w, k) ; /* unmark node k */
22 return (top) ; /* s [top..n-1] contains pattern of L(k,:)*/
23 }
24