Bug with GPU version

[artuuuro]

GPU version has a bug which makes the results incorrect.

[artuuuro]

Bug is related to compute language < 70.

[artuuuro]

Changed default values as a workaround for the bug (temporary).
commit 14ef50d

[correaa]

This calls for a regression test https://en.wikipedia.org/wiki/Regression_testing , that is an a posteriori test to not repeat the same bug in the future.

I recommend looking into Catch2 or Boost.Test to add a suite of tests.