79 lines
2.4 KiB
JavaScript
79 lines
2.4 KiB
JavaScript
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import { csMarked } from './csMarked.js';
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import { csMark } from './csMark.js';
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import { csUnflip } from './csUnflip.js';
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/**
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* Depth-first search computes the nonzero pattern xi of the directed graph G (Matrix) starting
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* at nodes in B (see csReach()).
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*
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* @param {Number} j The starting node for the DFS algorithm
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* @param {Matrix} g The G matrix to search, ptr array modified, then restored
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* @param {Number} top Start index in stack xi[top..n-1]
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* @param {Number} k The kth column in B
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* @param {Array} xi 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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* @param {Array} pinv The inverse row permutation vector, must be null for L * x = b
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*
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* @return {Number} New value of top
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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 csDfs(j, g, top, xi, pinv) {
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// g arrays
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var index = g._index;
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var ptr = g._ptr;
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var size = g._size; // columns
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var n = size[1]; // vars
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var i, p, p2; // initialize head
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var head = 0; // initialize the recursion stack
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xi[0] = j; // loop
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while (head >= 0) {
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// get j from the top of the recursion stack
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j = xi[head]; // apply permutation vector
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var jnew = pinv ? pinv[j] : j; // check node j is marked
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if (!csMarked(ptr, j)) {
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// mark node j as visited
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csMark(ptr, j); // update stack (last n entries in xi)
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xi[n + head] = jnew < 0 ? 0 : csUnflip(ptr[jnew]);
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} // node j done if no unvisited neighbors
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var done = 1; // examine all neighbors of j, stack (last n entries in xi)
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for (p = xi[n + head], p2 = jnew < 0 ? 0 : csUnflip(ptr[jnew + 1]); p < p2; p++) {
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// consider neighbor node i
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i = index[p]; // check we have visited node i, skip it
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if (csMarked(ptr, i)) {
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continue;
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} // pause depth-first search of node j, update stack (last n entries in xi)
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xi[n + head] = p; // start dfs at node i
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xi[++head] = i; // node j is not done
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done = 0; // break, to start dfs(i)
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break;
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} // check depth-first search at node j is done
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if (done) {
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// remove j from the recursion stack
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head--; // and place in the output stack
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xi[--top] = j;
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}
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}
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return top;
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}
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