Tensor .select() with mixed tensor/scalar arguments

Submitted by Tobias Wood

Assigned to Nobody

Link to original bugzilla bug (#1772)
Version: 3.4 (development)

Description

As discussed on the mailing list, the following program does not compile:

#include <unsupported/Eigen/CXX11/Tensor>

int main(const int argc, const char *const argv[])
{
Eigen::Tensor<float, 2> ft_A(2, 4), ft_B(2, 4), ft_result(2, 4);
ft_A.setRandom();
ft_B.setZero();
ft_result = (ft_A < 0.5f).select(ft_A, ft_B);
ft_result = (ft_A < 0.5f).select(ft_A, 0.f);
}

The first call to ft_result compiles fine, but the second does not because the second argument is a scalar.

Further notes from Christoph:

Your code works fine with Eigen::ArrayXXf instead of
Eigen::Tensor<float,2>, so making this work for Tensor as well would
not be a bad idea. Feel free to open a bug for that.

As a workaround, you can write:

 ft_result = (ft_A < 0.5f).select(ft_A, ft_A.constant(0.0f));  

This is also inconsistent with the Array-API, where you would need to
write (instead of ft_A.constant(0.0f)):
ArrayXXf::Constant(0.0f, ft_A.rows(), ft_A.cols());