SyCL branch compilation instructions for CUDA backend

[kostrzewa]

Are there any compilation instructions for the CUDA backend of the sycl branch of Grid? It seems that the build system does not automatically use nvcc where necessary. I've tried messing with OMPI_MPICXX but this makes configure fail. If you have a configure line lying around using OpenMPI and GCC, this would be rather helpful!

[kostrzewa]

The following sems to at least pass configure, but I'm not sure if I'm passing all required flags:

CXX=nvcc \
MPICXX=mpicxx \
CXXFLAGS="-gencode=arch=compute_61,code=compute_61 -std=c++11" \
~/code/grid_sycl/configure \                                                                                                                
  --enable-precision=double \
  --enable-simd=GPU \
  --enable-accelerator=cuda \
  --enable-comms=mpi-auto \
  --prefix=$(pwd)/install_dir

[paboyle]

I'm using:

../configure\
--prefix /ccs/home/paboyle/prefix \
--enable-precision=double\
--enable-unified=yes \
--enable-accelerator=cuda \
--enable-summit \
--enable-comms=mpi \
--enable-simd=GPU \
CXX=nvcc \
CXXFLAGS="-ccbin mpicxx -gencode arch=compute_70,code=sm_70 -I/ccs/home/paboyle/prefix/include/ -std=c++11" \
LDFLAGS=-L/ccs/home/paboyle/prefix/lib/ 

on summit

[kostrzewa]

Thanks! Just one more question for now: is it normal that the CayleyFermion instantiations take hours to compile?

[paboyle]

Not hours - I'm used to ~20 minutes with make -j which isn't great but not intolerable.

[kostrzewa]

Strange, it took my Ryzen5 3600 almost 8 hours to compile grid (gcc 8.4.0) with the configure line that I gave above in https://github.com/paboyle/Grid/issues/294#issuecomment-647559858

[paboyle]

wow.... and I thought power 9 was bad.... You are using parallel make?

[kostrzewa]

Yes, running on all cores :) Time to get a threadripper as a dev machine methinks...