gem5 / testing / jenkins-gem5-prod / 6d8694a5fb5cfb905186249581cc6a3fde6cc38a / . / src / sim / linear_solver.cc

/* | |

* Copyright (c) 2015 ARM Limited | |

* All rights reserved | |

* | |

* The license below extends only to copyright in the software and shall | |

* not be construed as granting a license to any other intellectual | |

* property including but not limited to intellectual property relating | |

* to a hardware implementation of the functionality of the software | |

* licensed hereunder. You may use the software subject to the license | |

* terms below provided that you ensure that this notice is replicated | |

* unmodified and in its entirety in all distributions of the software, | |

* modified or unmodified, in source code or in binary form. | |

* | |

* Redistribution and use in source and binary forms, with or without | |

* modification, are permitted provided that the following conditions are | |

* met: redistributions of source code must retain the above copyright | |

* notice, this list of conditions and the following disclaimer; | |

* redistributions in binary form must reproduce the above copyright | |

* notice, this list of conditions and the following disclaimer in the | |

* documentation and/or other materials provided with the distribution; | |

* neither the name of the copyright holders nor the names of its | |

* contributors may be used to endorse or promote products derived from | |

* this software without specific prior written permission. | |

* | |

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |

* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |

* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |

* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |

* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |

* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |

* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |

* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |

* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |

* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |

* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |

* | |

* Authors: David Guillen Fandos | |

*/ | |

#include "sim/linear_solver.hh" | |

std::vector <double> | |

LinearSystem::solve() const | |

{ | |

// Solve using gauss elimination, not ideal for big matrices | |

std::vector < LinearEquation > smatrix = this->matrix; | |

unsigned order = smatrix.size(); | |

for (unsigned row = 0; row < order - 1; row++) { | |

// Look for a non-zero row, and swap | |

for (unsigned i = row; i < order; i++) { | |

if (smatrix[i][row] != 0.0f) { | |

if (i != row) { | |

LinearEquation tmp = smatrix[i]; | |

smatrix[i] = smatrix[row]; | |

smatrix[row] = tmp; | |

} | |

break; | |

} | |

} | |

// Divide row by leading number to make it 1.0 | |

smatrix[row] *= (1.0f / smatrix[row][row]); | |

// Add it (properly scaled) to the rows below | |

for (unsigned i = row + 1; i < order; i++) { | |

LinearEquation t = smatrix[row]; | |

t *= -1.0f * smatrix[i][row]; | |

smatrix[i] = smatrix[i] + t; | |

} | |

} | |

// smatrix is now a triangular matrix with diagonal being 1 | |

// Just backproagate variable values from order-1 till 0 | |

std::vector <double> ret(order, 0.0f); | |

for (int row = order - 1; row >= 0; row--) { | |

// Unknown value | |

ret[row] = -smatrix[row][smatrix[row].cnt()] / smatrix[row][row]; | |

// Propagate variable in the cnt term | |

for (int i = row - 1; i >= 0; i--) { | |

smatrix[i][smatrix[i].cnt()] += ret[row] * smatrix[i][row]; | |

smatrix[i][row] = 0.0f; | |

} | |

} | |

return ret; | |

} |