Fprettify breaks cuda calls

[kaanolgu]

fprettify breaks CUDA Fortran triple-chevron syntax (<<<...>>>)

Description

After running fprettify, the build for #266 broke with multiple syntax errors from the NVHPC compiler:

[ 21%] Building Fortran object src/CMakeFiles/x3d2.dir/backend/cuda/poisson_fft.f90.o
NVFORTRAN-S-0034-Syntax error at or near < (/home/kolgu/x3d2/src/backend/cuda/poisson_fft.f90: 621)
  0 inform,   0 warnings,   1 severes, 0 fatal for fft_postprocess_100_cuda
NVFORTRAN-S-0034-Syntax error at or near < (/home/kolgu/x3d2/src/backend/cuda/poisson_fft.f90: 753)
  0 inform,   0 warnings,   1 severes, 0 fatal for fft_postprocess_110_cuda
NVFORTRAN-S-0034-Syntax error at or near < (/home/kolgu/x3d2/src/backend/cuda/poisson_fft.f90: 968)
NVFORTRAN-S-0034-Syntax error at or near < (/home/kolgu/x3d2/src/backend/cuda/poisson_fft.f90: 975)
  0 inform,   0 warnings,   2 severes, 0 fatal for enforce_periodicity_xy_cuda
NVFORTRAN-S-0034-Syntax error at or near < (/home/kolgu/x3d2/src/backend/cuda/poisson_fft.f90: 1011)
NVFORTRAN-S-0034-Syntax error at or near < (/home/kolgu/x3d2/src/backend/cuda/poisson_fft.f90: 1018)
  0 inform,   0 warnings,   2 severes, 0 fatal for undo_periodicity_xy_cuda
make[2]: *** [src/CMakeFiles/x3d2.dir/build.make:637: src/CMakeFiles/x3d2.dir/backend/cuda/poisson_fft.f90.o] Error 2

Root Cause

fprettify is inserting spaces into the CUDA Fortran kernel launch syntax (<<<...>>>).

Before fprettify:

call process_spectral_010<<<blocks, threads>>>( & !&

After fprettify:

call process_spectral_010 <  <  < blocks, threads >  >  > ( &

The inserted spaces break the triple-chevron syntax, which the NVHPC compiler then rejects.

[kaanolgu]

fortran-lang/fprettify#162 This requires a merge which has been a while so we might need to install it from this commit rather than the pip install

[ia267]

We currently have a workaround for this in x3d2 until that PR gets merged: https://x3d2.readthedocs.io/en/latest/developer/style.html#

CUDA Fortran chevron syntax is not supported by fprettify. To handle this, use !& to deactivate fprettify on lines where chevron syntax is used.

call gpu_kernel<<<blocks, threads>>>(args, ...) !&

[kaanolgu]

The PR is merged in now, so it should be fine without a workaround!