gem5  v22.0.0.1
linear_solver.cc
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37 
38 #include "sim/linear_solver.hh"
39 
40 namespace gem5
41 {
42 
45 {
46  // Solve using gauss elimination, not ideal for big matrices
47  std::vector < LinearEquation > smatrix = this->matrix;
48 
49  unsigned order = smatrix.size();
50  for (unsigned row = 0; row < order - 1; row++) {
51  // Look for a non-zero row, and swap
52  for (unsigned i = row; i < order; i++) {
53  if (smatrix[i][row] != 0.0f) {
54  if (i != row) {
55  LinearEquation tmp = smatrix[i];
56  smatrix[i] = smatrix[row];
57  smatrix[row] = tmp;
58  }
59  break;
60  }
61  }
62 
63  // Divide row by leading number to make it 1.0
64  smatrix[row] *= (1.0f / smatrix[row][row]);
65 
66  // Add it (properly scaled) to the rows below
67  for (unsigned i = row + 1; i < order; i++) {
68  LinearEquation t = smatrix[row];
69  t *= -1.0f * smatrix[i][row];
70  smatrix[i] = smatrix[i] + t;
71  }
72  }
73 
74  // smatrix is now a triangular matrix with diagonal being 1
75  // Just backproagate variable values from order-1 till 0
76  std::vector <double> ret(order, 0.0f);
77  for (int row = order - 1; row >= 0; row--) {
78  // Unknown value
79  ret[row] = -smatrix[row][smatrix[row].cnt()] / smatrix[row][row];
80  // Propagate variable in the cnt term
81  for (int i = row - 1; i >= 0; i--) {
82  smatrix[i][smatrix[i].cnt()] += ret[row] * smatrix[i][row];
83  smatrix[i][row] = 0.0f;
84  }
85  }
86 
87  return ret;
88 }
89 
90 } // namespace gem5
gem5::LinearSystem::solve
std::vector< double > solve() const
Definition: linear_solver.cc:44
gem5::VegaISA::f
Bitfield< 56 > f
Definition: pagetable.hh:53
std::vector< double >
gem5::ArmISA::i
Bitfield< 7 > i
Definition: misc_types.hh:67
gem5::VegaISA::t
Bitfield< 51 > t
Definition: pagetable.hh:56
gem5::LinearEquation
This class describes a linear equation with constant coefficients.
Definition: linear_solver.hh:55
linear_solver.hh
gem5::LinearSystem::matrix
std::vector< LinearEquation > matrix
Definition: linear_solver.hh:134
gem5
Reference material can be found at the JEDEC website: UFS standard http://www.jedec....
Definition: gpu_translation_state.hh:37

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