Re: [eigen] Using Triangular Views

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

I can confirm that this is an issue.
Somewhat related is this bug which at the moment is only worked-around:
http://eigen.tuxfamily.org/bz/show_bug.cgi?id=879

Triang*Triang did not work in 3.2 either, it seems.

I think for 3.3 we should at least work-around this (similar to bug 879)


Christoph


On 2016-08-30 14:09, Brad Bell wrote:
> How does one multiply a lower triangular matrix times a lower triangular
> matrix and avoid multiplying the zeros in the lower triangular matrix ?
>
> An attempt at this (see below) does not seem to compile when
> MULTIPLY_VIEW is non-zero: To be specific, I get the error message:
>
> error: no match for ‘operator*’ (operand types are ‘const
> Eigen::TriangularView<Eigen::Matrix<double, 2, 2>, 1u>’ and ‘const
> Eigen::TriangularView<Eigen::Transpose<Eigen::Matrix<double, 2, 2> >, 2u>’)
>     matrix B = view_L * view_L.transpose();
>
> when I try to compile the program:
> # include <Eigen/Core>
> # include <iostream>
>
> // code does not compile if you select MULTIPLY_VIEW equal to 1
> # define MULTIPLY_VIEW 0
>
> int main()
> {   typedef Eigen::Matrix<double, 2, 2> matrix;
>     using Eigen::Lower;
>     using Eigen::TriangularView;
>
>     matrix A;
>     A <<
>     1, 2,
>     3, 4;
>     //
>     const TriangularView<matrix, Lower> view_L = A.triangularView<Lower>();
>     matrix L = view_L;
>     //
> # if MULTIPLY_VIEW
>     matrix B = view_L * view_L.transpose();
> # else
>     matrix B = view_L * L.transpose();
> # endif
>     //
>     std::cout << "B =\n" << B << "\n";
>
>     return 0;
> }

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

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