[Wien] MPI parallel execution take much time than nonparallel on the same case on the multiprosesor single machine

[Laurence Marks]

How many cores do you have, and what version of mpi are you using?
Running mpi with only 3 processes on one machine is almost certainly
not going to be efficient and for that just stay with non-mpi. With a
dual quadcore (8 cores) or more it can be, provided that the mpi
version you use optimizes well.

N.B., for mpi you want OMP_NUM_THREADS=1, threads and mpi conflict.

On Thu, Apr 26, 2012 at 11:11 AM, jam <hassan.jamnejad at gmail.com> wrote:
> dear all
> recently I switch to MPI parallel execution.I compile the
> scalapack.2.0.1 and GotoBLAS2 and recompiled wien2k sources.bellow you
> will see the compiler option which I set for compiling the wien2k.
>
> Current settings:
>  O   Compiler options:        -ffree-form -O2 -ffree-line-length-none
>  L   Linker Flags:            $(FOPT) -L/home/GotoBLAS2 -lpthread
>  P   Preprocessor flags       '-DParallel'
>  R   R_LIB (LAPACK+BLAS):     -lgoto2 -lpthread
>
>
> Current parallel compilation option settings:
>     RP  RP_LIB(SCALAPACK+PBLAS): -lgoto2 -L/home/scalapack -lscalapack -lmpi -ldfftw_mpi -ldfftw
>     FP  FPOPT(par.comp.options): -ffree-form -O2
>     MP  MPIRUN commando        : mpirun -np _NP_ -machinefile _HOSTS_ _EXEC_
>
> unfortunately upon execution on the same test case file the cycles execution fall in long time execution on lapw1para.
> the .machines file is as bellow too:
> 1:localhost:3
> granularity:1
> extrafine:1
>
> also I have set OMP_NUM_THREADS to 4 in .bashrc and the OS istalled on the machine is openSUSE-11.4.
>
> I would appreciate if anyone can help me on the issue.
> kind regard
> hassan
>
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi