Hello. I have a computer with 16 cores in one node. In 4 of these cores, I performed electronic property calculations using the Wien2k package.
In the remaining 12 cores, I want to run 2 new calculations with VASP. That is, I want to run structure optimization on two large supercells (each occupies 6 cores). Is it possible to simultaneously (but not depending on each other) run calculations via Wien2k and VASP?.
If so, how do I tweak the INCAR file parameters, especially NPAR, NCORE...., to speed up VASP calculations without reducing cutoff energy and number of k-points. To start calculations in 6 cores per 1 task, I use the nohup mpirun -np 6 vasp_std>log& command, but I don’t know how to properly configure the INCAR file.
Thanks in advance!
Dear Dilshod D. Nematov
As per my experience and HPC configurations I used to have, I believe it is not good to run Wien2k and VASP simultaneously on one node, might be different cores. It may create some problems, and also will slow down the calculations. I tried it with two different vasp calculations, but it didn't work well.
and regarding NPAR or NCORE, up to where I realized, only NPAR helped me in speeding up the calculations, and for 6 cores per task, NPAR can't work, as it should be the square root of the number of cores we are using. like if you are using no. of cores as 4, then NPAR = 2 should be used.
While, NCORE should be equal to the number of cores you are using, but it never helped me.
Hope it helps!
Best wishes,
Payal.
Hello,
I would use NPAR = 2 in the INCAR and then if you run vasp with mpi you set the number of processors to 6 something like mpirun -np 6 vasp_std. You can check in the vasp wiki https://www.vasp.at/wiki/index.php/NCORE, they suggest to use NPAR instead of NCORE. In summary NPAR = sqrt(#processors) so in your case sqrt(6) ~ 2 though you could try aswell NPAR = 3, you can test which on is better. Then NCORE you just do not set the tag in the INCAR. On top of that you may try to use the taggs NSIM = 2 or 4 you can test which one works better.
Bests
Thank you so much for your answers dear Payal Wadhwa and Álvaro Adrián Carrasco Álvarez.
I have already found a good solution to this problem by doing some tests, and your recommendations helped me too.
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