I was playing with my diode test circuit again and found that one of the underlying issues is the simple row permutation algorithm I used in the LU decomposition class. The matrix is so sparse that it really is a problem. =( There probably is a textbook solution but I"m too lazy to go into my library in the other room right now. =P
Here's the permutation algorithm from matrix.cpp:
// do row permutations;
if(k >= max_k) {
double max = std::abs(m_mat->at(k,k));
unsigned int row = k;
for(unsigned int j = k + 1; j < n; j++) {
double val = std::abs(m_mat->at(j,k));
if(val > max) {
max = val;
row = j;
}
}
if(row != k) swapRows(k,row);
}
It doesn't work because one of the diagonal entries ended up being zero.
=( (see cell 9H on the spreadsheet).
The code would work if it were smart enough to know that it should have
swapped row 3 and row 8... (see attached).
If we can fix this, we can remove the expensive assertion checks from
the code which will make it really fly!!!
--
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badPermute.ods
Description: application/vnd.oasis.opendocument.spreadsheet
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