[Wien] MPI vs multi-thread?

[Hu, Wenhao]

Hi, all:

I met some confusions when I try to compare the efficiency of MPI and multi-thread calculations. In the lapw1 stage of the same case, I found that MPI will take double time of that with multi-thread. Other than, it even takes longer time than k-point parallelization without multi-thread setup. Can anyone tell me under what case MPI has a better performance? Another question is about the number of thread per job. When I increase the OMP_NUM_THREADS from 2 to 4, my process usually crashes after two cycles although it does have a boost effect on the finished cycle. Is this a normal thing? Do we have an optimal threads number?

Best,
Wenhao