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Subject: Re: [OMPI users] MPI loop problem
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-08-19 12:29:13

Julia He wrote:
does the problem show up even if you turn MPI off?
My answer: Yes and No. Yes, when I used ifort compiler. But the problem did not show up when I used gfortran, which was much slower.
Okay.  So, if this is not an MPI problem, as much as we like you and wish you luck, this mail list might not be the best place to resolve this problem!  :^)

Humor aside, there appears to be something special about how the code is compiled, and the code looks like it's non-trivial.  So, you probably need to pursue this issue somewhere other than this mail list.  I don't know what resources are available to you for pursuing ifort issues.

Since you have a working and non-working version, maybe there are ways of "divide and conquer" to isolate what the essential difference is between the two.  E.g., does the ifort version work at lower optimization levels?  Etc.

Good luck.  I'm sorry, but this mail alias probably isn't the right place to resolve this particular problem.
So, I think I can conclude that the problem is related to the Intel compiler -- ifort. I guess the mpif90 and mpif77 are wrappers to ifort.
(I should know this, but OMPI man pages should probably tell you for sure.)  I suspect the mpi wrappers can be used to invoke "any" compiler.  In any case, it appears you've isolated the problem to be due to the underlying compilers and not to an MPI component.
Do you know how to solve this problem? Is there any flag that I need to use in ifort?
Sorry, I'm not familiar with ifort.