The LLVM compiler supports several accelerated programming models including OpenMP, HIP, opencl, stdpar, hipfort, raja, and kokkos. Acceleration with OpenMP is available for FORTRAN, c, and C++. These examples demonstrate how to use the LLVM compiler to compile and execute applications using these different programming models and various utilities to support development.
The examples are divided into categories. These categories are:
- OpenMP C++ and c examples of OpenMP target offload
- FORTRAN FORTRAN examples of OpenMP target offload
- HIP Acceleration with HIP
- Raja Examples that use the RAJA programming model
- Kokkos Examples that use the kokkos programming model
- tools Examples on how to use profiling, debug, and address sanitizer tools
- stress Examples that are complex or stress resources
Eventually we will add these categories:
- stdpar C++ stdpar examples
- opencl Examples of offloading with OpenCL
- hipfort FORTRAN examples that use FORTRAN HIP bindings
Each category is a directory and each example is a subdirectory of the category directory. Typically there is a Makefile for each example. That Makefile can be executed with either update access to the example directory or in a different directory since examples typically exist in a read-only installation directory. These commands show how to run an example from a writable tmp directory.
mkdir /tmp/demo ; cd /tmp/demo
EXROOT=/opt/rocm/share/openmp-extras/examples # The examples base directory.
make -f $EXROOT/openmp/veccopy/Makefile run
The above will compile and execute the openmp/veccopy example. The Makefile will print the compile and execute commands to your console.
Each Makefile typically includes the common Makefile helper file
Makefile.find_gpu_and_install_dir.
This include file finds the LLVM compiler and sets the environment
variable LLVM_INSTALL_DIR if not already preset by the user.
If not preset, or the value of LLVM_INSTALL_DIR specifies a nonexistant directory,
the Makefile searches this list of directories:
/opt/rocm/lib/llvm /usr/lib/aomp ./../../../llvm ~/rocm/aomp
The Makefile sets LLVM_INSTALL_DIR to the first directory it finds in the above list.
It is recommended that users of these examples preset LLVM_INSTALL_DIR
if they want to demo the compiler with something other than the last
installed ROCm compiler.
The include file then determines if there is an active GPU and
the GPU architecture (eg. gfx940, sm_70, etc).
It first checks for an active amdgpu kernel module
If there is an active amdgpu kernel, the LLVM compiler utility
$(LLVM_INSTALL_DIR)/bin/amdgpu-arch is used to set
the value LLVM_GPU_ARCH which instructs the compiler which GPU to compile for.
If no active amdgpu kernel module is found, the include file looks for an nvidia PCI
device and then uses the compiler utility $(LLVM_INSTALL_DIR)/bin/amdgpu-arch
to set the value LLVM_GPU_ARCH.
If no LLVM installation or GPU could be found, the example Makefile will fail. So if you want to demo the compiler with something other than the last installed ROCm compiler (which is typically found at /opt/rocm/lib/llvm), then it is recommended that users preset LLVM_INSTALL_DIR.
There are often other make targets to show different ways to build the binary.
E.g. to run with some debug output set OFFLOAD_DEBUG variable:
env OFFLOAD_DEBUG=1 make
env OFFLOAD_DEBUG=1 make run
Run make help to see all the possible demos of each example.