61 lines
1.7 KiB
JavaScript
61 lines
1.7 KiB
JavaScript
// Copyright (c) 2006-2024, Timothy A. Davis, All Rights Reserved.
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// SPDX-License-Identifier: LGPL-2.1+
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// https://github.com/DrTimothyAldenDavis/SuiteSparse/tree/dev/CSparse/Source
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/**
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* Permutes a sparse matrix C = P * A * Q
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*
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* @param {SparseMatrix} a The Matrix A
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* @param {Array} pinv The row permutation vector
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* @param {Array} q The column permutation vector
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* @param {boolean} values Create a pattern matrix (false), values and pattern otherwise
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*
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* @return {Matrix} C = P * A * Q, null on error
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*/
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export function csPermute(a, pinv, q, values) {
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// a arrays
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var avalues = a._values;
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var aindex = a._index;
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var aptr = a._ptr;
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var asize = a._size;
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var adt = a._datatype;
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// rows & columns
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var m = asize[0];
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var n = asize[1];
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// c arrays
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var cvalues = values && a._values ? [] : null;
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var cindex = []; // (aptr[n])
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var cptr = []; // (n + 1)
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// initialize vars
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var nz = 0;
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// loop columns
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for (var k = 0; k < n; k++) {
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// column k of C is column q[k] of A
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cptr[k] = nz;
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// apply column permutation
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var j = q ? q[k] : k;
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// loop values in column j of A
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for (var t0 = aptr[j], t1 = aptr[j + 1], t = t0; t < t1; t++) {
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// row i of A is row pinv[i] of C
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var r = pinv ? pinv[aindex[t]] : aindex[t];
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// index
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cindex[nz] = r;
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// check we need to populate values
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if (cvalues) {
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cvalues[nz] = avalues[t];
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}
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// increment number of nonzero elements
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nz++;
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}
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}
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// finalize the last column of C
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cptr[n] = nz;
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// return C matrix
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return a.createSparseMatrix({
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values: cvalues,
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index: cindex,
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ptr: cptr,
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size: [m, n],
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datatype: adt
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});
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} |