NBSEBLOCKV: Difference between revisions
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We recommend using parallelization over bands only if the number of MPI ranks in the calculation exceeds <math>\text{total ranks}</math>. | We recommend using parallelization over bands only if the number of MPI ranks in the calculation exceeds <math>\text{total ranks}</math>. | ||
{{NB|mind|The {{TAG|NBSEBLOCKV}} and {{TAG|NBSEBLOCKO}} tags are available as of VASP.6.5.0}} | |||
== Related tags and sections == | == Related tags and sections == | ||
{{TAG|BSE}}, {{TAG|NBSEBLOCKO}}, [[BSE calculations]], [[TDDFT calculations]] | {{TAG|BSE}}, {{TAG|NBSEBLOCKO}}, [[BSE calculations]], [[TDDFT calculations]] |
Revision as of 10:57, 14 June 2024
NBSEBLOCKV = [integer]
Default: NBSEBLOCKV | = -1 |
Description: NBSEBLOCKV specifies the blocking factor for the unoccupied states when setting up the BSE Hamiltonian.
By default, the construction of the BSE Hamiltonian in VASP is parallelized over k-points, such that each MPI rank can compute a pair of k-points. This way the BSE Hamiltonian setup can be parallelized with
or for spin-polarized case
- ,
where is the total number of k-points in the full Brillouin zone. However, if a large number of MPI ranks is used in a calculation with too few k-point, this leads to load imbalance, where some of the MPI ranks will have no data to compute. In such cases, it is recommended to use parallelization over bands. If the parallelization over bands is used, all occupied (unoccupied) bands are divided into
and
blocks, respectively.
Such a band blocking allows VASP to parallelize the setup of the matrix with
or for spin-polarized case
If neither nor is specified, no paralliziation over bands is used and and .
Mind: Parallelization over bands with NBSEBLOCKV does not work with the old BSE driver, i.e., IBSE=0 |
We recommend using parallelization over bands only if the number of MPI ranks in the calculation exceeds .
Mind: The NBSEBLOCKV and NBSEBLOCKO tags are available as of VASP.6.5.0 |
Related tags and sections
BSE, NBSEBLOCKO, BSE calculations, TDDFT calculations