52 lines
1.6 KiB
JavaScript
52 lines
1.6 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 { csDfs } from './csDfs.js';
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/**
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* The csReach function computes X = Reach(B), where B is the nonzero pattern of the n-by-1
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* sparse column of vector b. The function returns the set of nodes reachable from any node in B. The
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* nonzero pattern xi of the solution x to the sparse linear system Lx=b is given by X=Reach(B).
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*
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* @param {Matrix} g The G matrix
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* @param {Matrix} b The B matrix
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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
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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 csReach(g, b, k, xi, pinv) {
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// g arrays
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var gptr = g._ptr;
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var gsize = g._size; // b arrays
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var bindex = b._index;
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var bptr = b._ptr; // columns
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var n = gsize[1]; // vars
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var p, p0, p1; // initialize top
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var top = n; // loop column indeces in B
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for (p0 = bptr[k], p1 = bptr[k + 1], p = p0; p < p1; p++) {
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// node i
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var i = bindex[p]; // check node i is marked
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if (!csMarked(gptr, i)) {
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// start a dfs at unmarked node i
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top = csDfs(i, g, top, xi, pinv);
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}
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} // loop columns from top -> n - 1
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for (p = top; p < n; p++) {
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// restore G
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csMark(gptr, xi[p]);
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}
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return top;
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}
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