Re: question about efficiency of fortran in parallel environments

Hello,

On Fri, 27 May 2005 10:24:05 -0700, Randall Mackie
<rlmackie862@xxxxxxxxx> wrote:

<snip>

>One of the programmers in my company, who programs mainly in c,
>has said that my program could be made more efficient if it
>were converted from Fortran to C. I'm not sure I'm convinced
>of this at all, but I was hoping for some feedback from people
>who program in both Fortran and C, especially in parallel environments.

MPI is written in C, so there's an extra layer of call executed
for each MPI call. But that's one call/return per call.

An MPI procedure execution usually involves a switch to the OS
to start a communication (on both processes), then communicating
between processes. On a cluster, this means establishing
the logical connection between two processors.

Compared to which the extra call and return are very small.
Note that the extra call and return also apply to the C++ binding
as well.

>Other people (the PETSc programmers) have said it doesn't make any difference whether I use
>C or Fortran. But, we have to make a decision, and I'm afraid I
>don't know the correct answer as I seem to be getting conflicting
>advice. Any help would be appreciated.

Trying to learn a new programming language to save a clock cycle
here and there is unlikely to succeed.

As soon as you have an f03 compiler, you could call the C binding
directly from Fortran, and shave those few cycles as well.

>Thanks in advance.
>
>Randy Mackie

--
Cheers!

Dan Nagle
Purple Sage Computing Solutions, Inc.
.

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