I just experienced a really annoying Eigen gotcha. If I have a sparsematrix A, defined as:
SparseMatrix<double> A;
// ... filled in somehow
then I can loop over the values with:
for(int k=0; k<A.outerSize(); ++k)
{
// Iterate over inside
for(SparseMatrix<double>::InnerIterator it (A,k); it; ++it)
{
// it.row(), it.col(), it.value()
}
}
This works fine. But if instead I use the wrong type for the InnerIterator, say int, I get no complaint from the compiler, just occasional garbage when I use it.col(), it.row(), or it.value():
for(int k=0; k<A.outerSize(); ++k)
{
// Iterate over inside
for(SparseMatrix<int>::InnerIterator it (A,k); it; ++it)
{
// it.row(), it.col(), it.value() produce occasional garbage
}
}