66 lines
1.7 KiB
JavaScript
66 lines
1.7 KiB
JavaScript
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import { csMark } from './csMark.js';
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import { csMarked } from './csMarked.js';
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/**
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* Find nonzero pattern of Cholesky L(k,1:k-1) using etree and triu(A(:,k))
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*
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* @param {Matrix} a The A matrix
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* @param {Number} k The kth column in A
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* @param {Array} parent The parent vector from the symbolic analysis result
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* @param {Array} w The nonzero pattern xi[top] .. xi[n - 1], an array of size = 2 * n
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* The first n entries is the nonzero pattern, the last n entries is the stack
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*
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* @return {Number} The index for the nonzero pattern
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*
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* Reference: http://faculty.cse.tamu.edu/davis/publications.html
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*/
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export function csEreach(a, k, parent, w) {
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// a arrays
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var aindex = a._index;
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var aptr = a._ptr;
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var asize = a._size; // columns
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var n = asize[1]; // initialize top
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var top = n; // vars
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var p, p0, p1, len; // mark node k as visited
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csMark(w, k); // loop values & index for column k
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for (p0 = aptr[k], p1 = aptr[k + 1], p = p0; p < p1; p++) {
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// A(i,k) is nonzero
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var i = aindex[p]; // only use upper triangular part of A
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if (i > k) {
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continue;
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} // traverse up etree
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for (len = 0; !csMarked(w, i); i = parent[i]) {
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// L(k,i) is nonzero, last n entries in w
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w[n + len++] = i; // mark i as visited
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csMark(w, i);
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}
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while (len > 0) {
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// decrement top & len
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--top;
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--len; // push path onto stack, last n entries in w
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w[n + top] = w[n + len];
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}
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} // unmark all nodes
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for (p = top; p < n; p++) {
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// use stack value, last n entries in w
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csMark(w, w[n + p]);
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} // unmark node k
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csMark(w, k); // s[top..n-1] contains pattern of L(k,:)
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return top;
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}
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