NBLOCK_FOCK
NBLOCK_FOCK = [integer]
| Default: NBLOCK_FOCK | = 64 | CPU build |
| = 32 | GPU build (OpenACC/OpenMP offload)) | |
= OMP_NUM_THREADS
|
CPU build that is compiled with OpenMP support and threading is active (OMP_NUM_THREADS > 1)
|
Description: Sets the number of orbitals that are processed simultaneously when computing the action of the Fock potential.
Instead of computing the action of the Fock potential on one orbital at a time, up to NBLOCK_FOCK orbitals are gathered and processed at once. This enables the use of matrix-matrix operations rather than matrix-vector operations, which is beneficial for performance on modern hardware.
Tuning NBLOCK_FOCK can significantly affect both the performance and memory consumption of hybrid functional calculations. Especially on GPUs, NBLOCK_FOCK should be tuned carefully to achieve optimal performance.
| Tip: On GPU architectures, the optimal value of NBLOCK_FOCK depends strongly on the specific hardware and the number of bands. It is recommended to experiment with values in the range 16-64. |