| 6:25:08 AM PDT - Tue, Jun 10th 2014 |
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Hello,
we are having problems with parallel scaling of NWChem on our supercomputer. We measured little or no parallel speedup with small test cases running on 1-128 CPUs.
For example, times for examples/qmd/3carbo.nw :
NCPU time[s]
1 401,509
2 276,147
4 193,832
8 119,013
16 118,552
32 228,424
64 331,187
128 1362,602
Other tests show worse results, for example calculating energy of (H2O)2 H: aug-cc-pVDZ, O: aug-cc-pVTZ, CCSD, the time of parallel calculation is always worse than when using only 1 CPU.
The computer is a Linux x86_64 cluster with Infiniband (Anselm). NWChem version 6.3-rev2, compiled with Intel. We tested both Intel MPI and Open MPI.
Is there some problem with our configuration or the input systems are just too small for NWChem parallelization?
Any help would be appreciated,
Martin Stachon
VSB-TU Ostrava & IT4Innovations
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