CPU vs GPU build trees (quick reference)¶

Use separate build directories for CPU and CUDA (or HIP) so you never mix object files or cached flags between toolchains.

Variant	Suggested directory	Defining CMake options
CPU	`build-cpu`	Default: CUDA and HIP off. MPI, FFTW, and HeFFTe (CPU/FFTW) required.
CUDA	`build-gpu`	`-DOpenPFC_ENABLE_CUDA=ON`, `-DCMAKE_CUDA_ARCHITECTURES=` matching the GPU (e.g. `86` for compute capability 8.6). HeFFTe must be built with CUDA enabled.
HIP	`build-hip`	`-DOpenPFC_ENABLE_HIP=ON`. HeFFTe with ROCm; see INSTALL.md §9.

Why two trees: The CUDA flag changes which translation units and libraries are built; reusing one build dir after toggling GPU options often leaves stale CMakeCache.txt entries. A clean configure per variant avoids that.

Authors’ workflow (condensed):

HeFFTe lives under $HOME/opt/heffte/2.4.1-cpu or 2.4.1-cuda (see INSTALL.md §3). Point OpenPFC at the right prefix with CMAKE_PREFIX_PATH (or a personal module that sets it).

# CPU (after module load gcc + openmpi, and HeFFTe installed to 2.4.1-cpu)
export CC=$(which gcc)
export CXX=$(which g++)
export CMAKE_PREFIX_PATH=$HOME/opt/heffte/2.4.1-cpu:$CMAKE_PREFIX_PATH
cmake -DCMAKE_BUILD_TYPE=Release -S . -B build-cpu
cmake --build build-cpu -j"$(nproc)"

# CUDA (HeFFTe with CUDA at 2.4.1-cuda; nvcc on PATH)
export CMAKE_PREFIX_PATH=$HOME/opt/heffte/2.4.1-cuda:$CMAKE_PREFIX_PATH
cmake -DCMAKE_BUILD_TYPE=Release \
      -DOpenPFC_ENABLE_CUDA=ON \
      -DCMAKE_CUDA_ARCHITECTURES=native \
      -S . -B build-gpu
cmake --build build-gpu -j"$(nproc)"

Full prerequisites (modules, HeFFTe layout, optional FetchContent fallback into build/ only) are in INSTALL.md §3 and §5–§9.

CPU vs GPU build trees (quick reference)¶

See also¶