Tests `NNLS_dependent_columns` and `NNLS_multi_core` may fail

[cpethrick]

A seed is set for a random number generator at line 788 of tests/unit_tests/linear_solver/NNLS_tests.cpp. Some seeds may cause the test to fail.

[tofstie]

This test failure is the result of the matrices in Tests "NNLS_dependent_columns" and "NNLS_wide_matrix" being generated with no solution guaranteed. There are two approaches to fix this test failure.

1. Find a random seed that does not fail

• This would involve changing line 788-790 to have a static seed, that would always reproduce the same expected matrices.

2. In the Optimality function, set the random flag to true

• This flag was originally added for when the NNLS is not guaranteed to have a solution. The Optimality function then uses the version of Optimality defined in the Eigen test cases, not the one that is used for the ESCW NNLS. By setting this random flag to true we would just the the optimality defined by the Eigen Package.

Either one or both fixes can be done, and I can submit a PR once I know which to do.