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* | |

* 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; | |

} |