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Subject: Re: [OMPI users] Question about OpenMPI performance vs. MVAPICH2
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-09-20 12:06:38

Excellent point that is often overlooked. Be sure you compiled
optimized - i.e., "mpicc -O3" (or whatever O-level you want).

OMPI's wrapper compilers do NOT contain optimization flags.

On Sep 20, 2009, at 9:50 AM, Jed Brown wrote:

> Brian Powell wrote:
>> I ran a final test which I find very strange: I ran the same test
>> case
>> on 1 cpu. The MVAPICH2 case was 23% faster!?!? This makes little
>> sense
>> to me. Both are using ifort as the mpif90 compiler using *identical*
>> optimization flags, etc. I don't understand how the results could be
>> different.
> Are you saying the output of mpicc/mpif90 -show has the same
> optimization flags? MPICH2 usually puts it's own optimization flags
> into the wrappers.
> Jed
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