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fix the 4x4 inverse -- unit test passes again

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This commit is contained in:
Benoit Jacob 2009-04-14 13:42:23 +00:00
parent 2bb1c9e8dc
commit 6ee4eb94fb
1 changed files with 15 additions and 5 deletions
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20
Eigen/src/LU/Inverse.h
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@ -132,21 +132,31 @@ void ei_compute_inverse_in_size4_case(const MatrixType& matrix, MatrixType* resu
// since this is a rare case, we don't need to optimize it. We just want to handle it with little
// additional code.
MatrixType m(matrix);
m.row(1).swap(m.row(2));
m.row(0).swap(m.row(2));
m.row(1).swap(m.row(3));
if(ei_compute_inverse_in_size4_case_helper(m, result))
{
// good, the topleft 2x2 block of m is invertible. Since m is different from matrix in that two
// good, the topleft 2x2 block of m is invertible. Since m is different from matrix in that some
// rows were permuted, the actual inverse of matrix is derived from the inverse of m by permuting
// the corresponding columns.
result->col(1).swap(result->col(2));
result->col(0).swap(result->col(2));
result->col(1).swap(result->col(3));
}
else
{
// last possible case. Since matrix is assumed to be invertible, this last case has to work.
m.row(1).swap(m.row(2));
// first, undo the swaps previously made
m.row(0).swap(m.row(2));
m.row(1).swap(m.row(3));
// swap row 0 with the the row among 0 and 1 that has the biggest 2 first coeffs
int swap0with = ei_abs(m.coeff(0,0))+ei_abs(m.coeff(0,1))>ei_abs(m.coeff(1,0))+ei_abs(m.coeff(1,1)) ? 0 : 1;
m.row(0).swap(m.row(swap0with));
// swap row 1 with the the row among 2 and 3 that has the biggest 2 first coeffs
int swap1with = ei_abs(m.coeff(2,0))+ei_abs(m.coeff(2,1))>ei_abs(m.coeff(3,0))+ei_abs(m.coeff(3,1)) ? 2 : 3;
m.row(1).swap(m.row(swap1with));
ei_compute_inverse_in_size4_case_helper(m, result);
result->col(1).swap(result->col(3));
result->col(1).swap(result->col(swap1with));
result->col(0).swap(result->col(swap0with));
}
}
}