mirror of
https://github.com/ton-blockchain/ton
synced 2025-03-09 15:40:10 +00:00
59 lines
2 KiB
C++
59 lines
2 KiB
C++
/*
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This file is part of TON Blockchain Library.
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TON Blockchain Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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TON Blockchain Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with TON Blockchain Library. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2017-2020 Telegram Systems LLP
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*/
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#include "td/fec/algebra/GaussianElimination.h"
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namespace td {
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Result<MatrixGF256> GaussianElimination::run(MatrixGF256 A, MatrixGF256 D) {
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const size_t cols = A.cols();
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const size_t rows = A.rows();
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CHECK(cols <= rows);
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std::vector<uint32> row_perm(rows);
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for (uint32 i = 0; i < rows; i++) {
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row_perm[i] = i;
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}
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for (size_t row = 0; row < cols; row++) {
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size_t non_zero_row = row;
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for (; non_zero_row < rows && A.get(row_perm[non_zero_row], row).is_zero(); non_zero_row++) {
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}
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if (non_zero_row == rows) {
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return Status::Error("Non solvable");
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}
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if (non_zero_row != row) {
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std::swap(row_perm[non_zero_row], row_perm[row]);
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}
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auto mul = A.get(row_perm[row], row).inverse();
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A.row_multiply(row_perm[row], mul);
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D.row_multiply(row_perm[row], mul);
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CHECK(A.get(row_perm[row], row).value() == 1);
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for (size_t zero_row = 0; zero_row < rows; zero_row++) {
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if (zero_row == row) {
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continue;
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}
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auto x = A.get(row_perm[zero_row], row);
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if (!x.is_zero()) {
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A.row_add_mul(row_perm[zero_row], row_perm[row], x);
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D.row_add_mul(row_perm[zero_row], row_perm[row], x);
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}
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}
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}
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return D.apply_row_permutation(row_perm);
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}
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} // namespace td
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