Determining which gencode (compute_, arch_) values I need for nvcc - within CMake

Question

I\'m using CMake as a build system for my code, which involves CUDA. I was thinking of automating the task of deciding which compute_XX and arch_XX

Answer 1

My strategy has been to compile and run a bash script that probes the card and returns the gencode for cmake. Inspiration came from University of Chicago's SLURM. To handle errors or multiple gpus or other circumstances, modify as necessary.

In your project folder create a file cudaComputeVersion.bash and ensure it is executable from the shell. Into this file put:

#!/bin/bash

# create a 'here document' that is code we compile and use to probe the card
cat << EOF > /tmp/cudaComputeVersion.cu
#include 
int main()
{
cudaDeviceProp prop;
cudaGetDeviceProperties(&prop,0);
int v = prop.major * 10 + prop.minor;
printf("-gencode arch=compute_%d,code=sm_%d\n",v,v);
}
EOF

# probe the card and cleanup
/usr/local/cuda/bin/nvcc /tmp/cudaComputeVersion.cu -o /tmp/cudaComputeVersion
/tmp/cudaComputeVersion
rm /tmp/cudaComputeVersion.cu
rm /tmp/cudaComputeVersion

And in your CMakeLists.txt put:

# at cmake-build-time, probe the card and set a cmake variable
execute_process(COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/cudaComputeVersion.bash OUTPUT_VARIABLE GENCODE)
# at project-compile-time, include the gencode into the compile options
set(CUDA_NVCC_FLAGS ${CUDA_NVCC_FLAGS}; "${GENCODE}")

# this makes CMake all chatty and allows you to see that GENCODE was set correctly
set(CMAKE_VERBOSE_MAKEFILE TRUE)

cheers