My Community

Dear VASP users,

We are running parallel jobs on a cluster, but the jobs doesn't scale up with the number of processors used. It
runs very slow. Does anybody konw how to fix this problem?
Is the problem that Lam MPI doesn't work near as well on these systems as the MPI versions designed for these computers (derivatives of MPICH MPI)? Thanks!

LAM is designed for clusters and works very well. At least as well as MPICH.

What's your interconnect? How are you setting up the parallelisation?

(Consider also OpenMPI, where the LAM development has now moved along with several other MPI implementation teams.)

I fully agree with forum member tjf.
Apart from that, please mind that there is a small part of VASP (about 2-3% of the code) which cannot be parallelized, therefore VASP will not scale exactly linearly with the number of processors. The performance in general is best for about 16 parallel processors.