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7f62fa2b66
* Subtle bug in kernel computation Coefficient was being passed by reference and, therefore, was being changed indirectly. In the process, updated the code to be more generic to avoid rational computation in the middle of matrix manipulation. * sparse_matrix: fixed handling of 0 in add_var() and add() particularly in add_var(), without the fix the user is responsible for checking coefficients for 0.
85 lines
2.2 KiB
C++
85 lines
2.2 KiB
C++
/*++
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Copyright (c) 2014 Microsoft Corporation
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Module Name:
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sparse_matrix_ops.h
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Abstract:
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Author:
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Nikolaj Bjorner (nbjorner) 2014-01-15
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Notes:
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--*/
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#pragma once
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#include "math/simplex/sparse_matrix.h"
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#include "util/rational.h"
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namespace simplex {
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class sparse_matrix_ops {
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public:
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template <typename Ext>
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static void kernel(sparse_matrix<Ext> &M, vector<vector<rational>> &K) {
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using scoped_numeral = typename Ext::scoped_numeral;
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vector<unsigned> d, c;
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unsigned n_vars = M.num_vars(), n_rows = M.num_rows();
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c.resize(n_rows, 0u);
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d.resize(n_vars, 0u);
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auto &m = M.get_manager();
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scoped_numeral m_ik(m);
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scoped_numeral D(m);
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for (unsigned k = 0; k < n_vars; ++k) {
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d[k] = 0;
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for (auto [row, row_entry] : M.get_rows(k)) {
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if (c[row.id()] != 0) continue;
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auto &m_jk = row_entry->m_coeff;
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if (mpq_manager<false>::is_zero(m_jk)) continue;
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// D = rational(-1) / m_jk;
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m.set(D, m_jk);
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m.inv(D);
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m.neg(D);
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M.mul(row, D);
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for (auto [row_i, row_i_entry] : M.get_rows(k)) {
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if (row_i.id() == row.id()) continue;
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m.set(m_ik, row_i_entry->m_coeff);
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// row_i += m_ik * row
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M.add(row_i, m_ik, row);
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}
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c[row.id()] = k + 1;
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d[k] = row.id() + 1;
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break;
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}
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}
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for (unsigned k = 0; k < n_vars; ++k) {
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if (d[k] != 0) continue;
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K.push_back(vector<rational>());
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for (unsigned i = 0; i < n_vars; ++i) {
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if (d[i] > 0) {
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auto r = sparse_matrix<mpq_ext>::row(d[i] - 1);
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K.back().push_back(rational(M.get_coeff(r, k)));
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} else if (i == k)
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K.back().push_back(rational(1));
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else
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K.back().push_back(rational(0));
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}
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}
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}
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static void kernel(sparse_matrix<mpq_ext> &M, vector<vector<rational>> &K) {
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kernel<mpq_ext>(M, K);
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}
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};
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} // namespace simplex
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