Parallelization

For many complex problems, a single core is not enough to finish the calculation in a reasonable time. VASP makes use of parallel machines splitting the calculation into many tasks. By default, VASP distributes the number of bands (NBANDS) over the available cores. But it is often beneficial to add parallelization over the FFTs (NCORE), the k points (KPAR), and separate calculations (IMAGES). All these tags default to 1 and divide the number of cores among the parallelization options. There may also be additional parallelization options for some algorithms in VASP.

$\text{total cores} = \text{cores parallelizing bands} \times \text{NCORE} \times \text{KPAR} \times \text{IMAGES} \times \text{other algorithm-dependent tags}$

VASP makes use of OpenMP and OpenACC when possible. Note that these options conflict with the NCORE parallelization.