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add internal comment (mostly a pretext to test the eigen-commits list)

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This commit is contained in:
Benoit Jacob 2009-05-20 16:54:40 +02:00
parent dd45c4805c
commit c7baddb132
2 changed files with 14 additions and 1 deletions
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9
Eigen/src/LU/LU.h
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@ -383,9 +383,16 @@ LU<MatrixType>::LU(const MatrixType& matrix)
}
if(k<rows-1)
m_lu.col(k).end(rows-k-1) /= m_lu.coeff(k,k);
if(k<size-1)
if(k<size-1) {
/* I know it's tempting to replace this for loop by a single matrix product. But actually there's no reason why it
* should be faster because it's just an exterior vector product; and in practice this gives much slower code with
* GCC 4.2-4.4 (this is weird, would be interesting to investigate). On the other hand, it would be worth having a variant
* for row-major matrices, traversing in the other direction for better performance, with a meta selector to compile only
* one path
*/
for(int col = k + 1; col < cols; ++col)
m_lu.col(col).end(rows-k-1) -= m_lu.col(k).end(rows-k-1) * m_lu.coeff(k,col);
}
}
for(int k = 0; k < matrix.rows(); ++k) m_p.coeffRef(k) = k;

6
Eigen/src/LU/PartialLU.h
View File

@ -197,6 +197,12 @@ PartialLU<MatrixType>::PartialLU(const MatrixType& matrix)
if(k<size-1) {
m_lu.col(k).end(size-k-1) /= m_lu.coeff(k,k);
/* I know it's tempting to replace this for loop by a single matrix product. But actually there's no reason why it
* should be faster because it's just an exterior vector product; and in practice this gives much slower code with
* GCC 4.2-4.4 (this is weird, would be interesting to investigate). On the other hand, it would be worth having a variant
* for row-major matrices, traversing in the other direction for better performance, with a meta selector to compile only
* one path
*/
for(int col = k + 1; col < size; ++col)
m_lu.col(col).end(size-k-1) -= m_lu.col(k).end(size-k-1) * m_lu.coeff(k,col);
}