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23 * this software without specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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37 * Authors: David Guillen Fandos
40 #include "sim/linear_solver.hh"
43 LinearSystem::solve() const
45 // Solve using gauss elimination, not ideal for big matrices
46 std::vector
< LinearEquation
> smatrix
= this->matrix
;
48 unsigned order
= smatrix
.size();
49 for (unsigned row
= 0; row
< order
- 1; row
++) {
50 // Look for a non-zero row, and swap
51 for (unsigned i
= row
; i
< order
; i
++) {
52 if (smatrix
[i
][row
] != 0.0f
) {
54 LinearEquation tmp
= smatrix
[i
];
55 smatrix
[i
] = smatrix
[row
];
62 // Divide row by leading number to make it 1.0
63 smatrix
[row
] *= (1.0f
/ smatrix
[row
][row
]);
65 // Add it (properly scaled) to the rows below
66 for (unsigned i
= row
+ 1; i
< order
; i
++) {
67 LinearEquation t
= smatrix
[row
];
68 t
*= -1.0f
* smatrix
[i
][row
];
69 smatrix
[i
] = smatrix
[i
] + t
;
73 // smatrix is now a triangular matrix with diagonal being 1
74 // Just backproagate variable values from order-1 till 0
75 std::vector
<double> ret(order
, 0.0f
);
76 for (int row
= order
- 1; row
>= 0; row
--) {
78 ret
[row
] = -smatrix
[row
][smatrix
[row
].cnt()] / smatrix
[row
][row
];
79 // Propagate variable in the cnt term
80 for (int i
= row
- 1; i
>= 0; i
--) {
81 smatrix
[i
][smatrix
[i
].cnt()] += ret
[row
] * smatrix
[i
][row
];
82 smatrix
[i
][row
] = 0.0f
;