vecpar

This is a header-only library for enabling single source code (C++) to target heterogeneous platforms (CPU, GPU). The project is still in early R&D phase.

Supported backends

• (CPU) OpenMP
• (GPU) CUDA
• (GPU) OpenMP target - experimental

Dependencies

Common dependencies for all the backends:

1. Vecmem library
2. GoogleTest

LLVM/clang is currently the only compiler that can build all the vecpar backends. Recommended setup on a system with NVIDIA GPU:

spack install llvm@14.0.0 +all_targets +cuda cuda_arch=<XY>
spack install vecmem +cuda cuda_arch=<XY>
spack install googletest

vecpar uses nestoroprysk/FunctionComposition for supporting the algorithm chaining functionality.

Dependency for the OpenMP for CPU backend

Any C/C++ compiler (with OpenMP support) can build the CPU OpenMP backend.

Dependency for the CUDA backend

For the CUDA backend, clang or nvcc can be used to compile the code. Additionally, the CUDA libraries must be accessible at compile and runtime.

Dependency for the OpenMP Target backend

To compile the GPU OpenMP backend, gcc/clang need a specific build configuration when targeting different GPU:

• NVIDIA - this can be easily achieved by installing gcc or llvm with flags +nvptx and +cuda respectively from spack.
• AMD - the configuration steps need to be done manually as show in the online documentation. For AMD GPU, AOMP compiler can be used as an alternative.

Also, the GPU driver and the associated libraries (CUDA or ROCm) need to be accessible at compile and runtime.

Installation

Get the code

git clone --recurse-submodules https://github.com/wr-hamburg/vecpar.git

To build the code

cmake -S <source_dir> -B <build_directory>

cmake --build <build_directory> \
       -DVECPAR_BUILD_OMP_BACKEND=On \ 
       -DVECPAR_BUILD_CUDA_BACKEND=On 

To enable the automated tests, set also -DVECPAR_BUILD_TESTS=On.

By default, all build options are enabled.

To compile for aarch64, set CC/CXX environment variables to appropriate aarch64 compilers.

To install the library

cmake --install <build_directory>

Usability

To use vecpar from a different project, add the following import line into the root cmake file:

find_package( vecpar REQUIRED 0.0.3)