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Hi,

I've encountered clearly SLOW speed of VASP 5.4.1(with patch #3),
when using intel compiler 14 and later and OpenMPI 1.6.5 and later.
No problem with VASP 5.3.5 or IntelMPI.
Does anyone have same experience ?
Would you share any advice and comments to resolve this?

Below are my performance data:

Input: 216 Si atoms, with PAW GGA
CPU: Intel Xeon E5-2698 v3
Number of MPI processes: 4

(a) VASP 5.4.1p3 / ic13.1.3 / OpenMPI 1.6.5 = 155 secs (good)
(b) VASP 5.4.1p3 / ic13.1.3 / OpenMPI 1.8.8 = 135 secs (good)
(c) VASP 5.4.1p3 / ic14.0.3 / OpenMPI 1.6.5 = 484 secs (SLOW!)
(d) VASP 5.4.1p3 / ic15.0.5 / OpenMPI 1.6.5 = 518 secs (SLOW!)
(e) VASP 5.4.1p3 / ic15.0.5 / OpenMPI 1.8.8 = 416 secs (SLOW!)
(f) VASP 5.4.1p3 / ic16.0.1 / OpenMPI 1.8.8 = 466 secs (SLOW!)
(g) VASP 5.4.1p3 / ic15.0.5 / IntelMPI 5.1.2 = 130 secs (good)
(h) VASP 5.3.5 / ic13.1.3 / OpenMPI 1.6.5 = 158 secs (good)
(i) VASP 5.3.5 / ic15.0.5 / OpenMPI 1.6.5 = 155 secs (good)
(j) VASP 5.3.5 / ic15.0.5 / OpenMPI 1.8.8 = 137 secs (good)
(k) VASP 5.3.5 / ic16.0.1 / IntelMPI 5.1.2 = 130 secs (good)

* When I try with other numbers of MPI processes(1,2,8,16,32), same SLOW speed is observed.

Thanks in advance,
HIROMASA

Hi,

Happily I've solved this problem myself. Here's the workaround.

In my VASP build cases with both OpenMPI and IntelMPI, I used ScaLAPACK of MKL.
When I tried NOT to use ScaLAPACK with OpenMPI, the speed became same as IntelMPI.
Since libmkl_scalapack_lp64 is used in common with both OpenMPI and IntelMPI,
the cause is BLACS in MKL, and only BLACS for IntelMPI works fine.

Thanks,
HIROMASA

Thank you for sharing your opinion.