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