Just to ensure I understand what you are saying: it appears that 1.8 is much
faster than 1.6.5 with the default settings, but slower when you set
btl=tcp,self?
This seems rather strange. I note that the 1.8 value is identical in the two
cases, but somehow 1.6.5 went much faster in the latter case. Is this a
copy/paste error?
On Apr 10, 2014, at 2:05 AM, Victor Vysotskiy <victor.vysots...@teokem.lu.se>
wrote:
> Dear Developers,
>
> I have faced a performance degradation on multi-core single processor
> machine. Specifically, in the most recent Open MPI v1.8 the initialization
> and process startup stage became ~10x slower compared to v1.6.5. In order to
> measure timings I have used the following code snippet:
>
> /*-------------------------------------------*/
> #include <mpi.h>
>
> int main (int argc, char *argv[]) {
>
> MPI_Init(&argc,&argv);
> MPI_Finalize();
>
> return 0;
> }
> /*-------------------------------------------*/
>
> The execution wall time has been measured in a trivial way by using the
> 'time' command, i.e.:
>
> time mpirun -np 2 ./a.out
>
> Below are given averaged timings for both versions on Linux x86_64 (Intel
> i7-3630):
>
> Default settings:
> 1.8 : 0.679 s
> 1.6.5: 1.041 s
>
> OMPI_MCA_btl=tcp,self:
> 1.8 : 0.679 s
> 1.6.5: 0.041 s
>
> The same problem has been detected on Mac OS X v10.9.2.
>
> Here I should stress that others MPI distributions perform as the OpenMPI
> v1.6.5 with the TCP byte transfer layer activated.
>
> So, I am wondering whether it is possible to tune v1.8 in order to boost the
> startup process? The problem is that during the automatic nightly
> verification of our program we usually spawn parallel binaries a thousands of
> times.
>
> Thank you In advance!
>
> Best regards,
> Victor.
>
>
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