OpenCL

CP2K can use OpenCL devices through the DBCSR and DBM/DBT offload paths. This supports GPUs and other devices that provide a suitable OpenCL implementation. The OpenCL backend relies on LIBXS and LIBXSTREAM; LIBXSMM may additionally be used through LIBXS.

OpenCL acceleration does not provide the CUDA/HIP GRID or PW GPU backends. It is therefore most useful for the DBCSR and DBM workloads supported by the OpenCL backend.

Installing OpenCL and preparing the runtime environment

An OpenCL build needs both development files at configuration time and an actual device driver at runtime:

CMake must be able to find OpenCL headers and the OpenCL loader library. On Debian and Ubuntu, the distribution packages are commonly named opencl-headers and ocl-icd-opencl-dev; package names vary on other systems.
The loader library alone is not enough to run CP2K. The system also needs an Installable Client Driver (ICD) provided by the device vendor or another OpenCL implementation. Vendor SDKs and runtimes, such as NVIDIA CUDA, AMD ROCm, or Intel’s compute runtime, may provide the necessary components, but their availability and installation layout are platform dependent.
For a manually managed installation in a non-standard prefix, make OpenCL, LIBXS, and LIBXSTREAM discoverable by CMake. CMAKE_PREFIX_PATH is usually the most convenient mechanism; see Build from Source for the general CMake workflow.
Set ACC_OPENCL_VERBOSE=2 to print information about generated kernels, or ACC_OPENCL_VERBOSE=3 to print information about executed kernels. These settings are useful for checking that CP2K reaches the intended OpenCL runtime and device.

Building CP2K with OpenCL-based DBCSR

Configure CP2K with CMake as usual and add:

cmake -S . -B build -GNinja \
  -DCP2K_USE_ACCEL=OPENCL \
  -DCP2K_USE_LIBXS=ON \
  -DCMAKE_PREFIX_PATH=/path/to/dependencies
cmake --build build --parallel

CP2K_USE_LIBXS=ON is required for the OpenCL backend. CMake also requires OpenCL and LIBXSTREAM, and the DBCSR installation selected by CMake must support the requested OpenCL configuration. The CMake summary identifies the discovered OpenCL and LIBXSTREAM dependencies. No GPU architecture needs to be specified for an OpenCL build.

CMake supplies the required compile definitions, include paths, and link dependencies. In particular, do not duplicate these settings through manually added compiler or linker flags.

The DBCSR OpenCL kernels use tuned small-matrix-multiplication parameters where available. The available parameter sets are embedded into the application, so the executable does not depend on a fixed external parameter-file location. If no suitable tuned parameters are available, DBCSR uses fallback defaults to construct kernels at runtime.

Set OPENCL_LIBSMM_SMM_PARAMS=/path/to/csv-file to override the built-in parameters for an existing application, or set OPENCL_LIBSMM_SMM_PARAMS=0 to disable them. See the DBCSR documentation for details on kernel-parameter tuning.

Building CP2K with the OpenCL-based DBM library

-DCP2K_USE_ACCEL=OPENCL also enables the OpenCL-capable DBM build path. The CP2K_ENABLE_DBM_GPU option is enabled by default when an accelerator backend is selected; set -DCP2K_ENABLE_DBM_GPU=OFF to build without DBM offload while retaining the rest of the selected configuration.

During the build, CMake generates the header that embeds the DBM OpenCL kernel source and adds the required target dependencies automatically. No additional build rule or generated source file has to be maintained by the user.

The CUDA/HIP-specific GRID and PW acceleration options do not enable corresponding OpenCL backends. To disable DBCSR acceleration explicitly, configure with -DCP2K_DBCSR_USE_CPU_ONLY=ON.