René Widera

> Maybe a specialization of the alpaka::math functions for complex numbers could be using funcitonallity from cuComplex.h instead? I do not remember exactly why we not use `cuComplex.h` but most...

The problem is ``` c = alpaka::sin(c); ``` because it must be ``` c = alpaka::sin(acc, c); ``` All math functions require the accelerator as first parameter.

The reason why this error happened is that we have implemented `sin()` https://github.com/alpaka-group/alpaka/blob/c2a37cc8c9dd82b45a203318bf6000febc460f45/include/alpaka/math/Complex.hpp#L532-L537 in the alpaka namepsace for Complex. I assume this is required for ADL.

The same file is showing that it is for host only https://github.com/alpaka-group/alpaka/blob/c2a37cc8c9dd82b45a203318bf6000febc460f45/include/alpaka/math/Complex.hpp#L352-L366

IMo the problem is that we defined our complex class within the `alpaka` namespace instead of `alpaka::internal`. We could move Complex into a namespace which is saying from the name...

Thanks for investigating it. Can we please disable the test in the source code for this compiler. There are alpaka macros to control the version.

Sry has overseen this issue. Never the less try try to answer it. I think you have not compiled with a CUDA or HIP compiler. For cuda you should have...

> How was this actually working? CUDA 11.x does not support C++20? nvcc

Mhhh PIConGPU is saying something else https://github.com/ComputationalRadiationPhysics/picongpu/blob/041cb1bef683d936785aea9cb07ca9a302e16e47/share/ci/n_wise_generator.py#L149, I will test if it works with 12.1

@SimeonEhrig I forgot ro rebase to habe the ulimit fix in. Will push the pr again asap