Re: [eigen] Permutation times Sparse matrix

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

This looks like an aliasing problem. Just assign the result to a new 
matrix. Ideally, we could implement a "permute{Rows,Cols}InPlace" method 
for that use case. And we should probably warn more explicitly that 
sparse products are not aliasing-save.

Christoph

On 2016-09-19 16:29, Brad Bell wrote:
> When I execute the program below I expect to get
> L=
> 1 0
> 0 1
> But I get
> L =
> 0 0
> 0 0
>
> # include <Eigen/SparseCore>
> # include <iostream>
> int main()
> {   Eigen::SparseMatrix<double> L(2,2);
>     L.insert(0,0) = 1.0;
>     L.insert(1,1) = 1.0;
>     Eigen::PermutationMatrix<2,2> P;
>     P.setIdentity();
>     L = P * L;
>     std::cout << "L =\n" << Eigen::Matrix<double,2,2>(L) << "\n";
>     return 0;
> }

--
 Dipl. Inf., Dipl. Math. Christoph Hertzberg

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