[Beowulf] newbie

Gus Correa gus at ldeo.columbia.edu
Thu Apr 30 13:07:36 EDT 2009


Hi Tomislav and list

John Hearns wrote:
> 2009/4/30 Lux, James P <james.p.lux at jpl.nasa.gov>:
>> Which means that the better compiler has economic value, which means that
>> someone can afford to pay for that compiler (and save money overall), which
>> means that a compiler vendor can afford to pay someone to care about
>> optimization full time.
> 
> James, that is EXACTLY my point.
> That is why I was speaking up in favour of commercial compilers - they
> are worth the money, and the people working for the companies
> producing them deserve to eat!
> 

I have had all sort of experiences here.
Code that only compiles with Gnu, code that only compiles with PGI,
code that only compiles with Intel, code that requires a hybrid approach
(gcc+ifort or gcc+pgf90), etc.
Similar for runtime: some code that compiles with commercial
compiler A may segfault at runtime, whereas the version compiled
with commercial compiler B or Gnu may run just fine and give correct
results.
Not to mention performance, that is not necessarily the best when you
pay for the compiler.

If you don't have funds to buy a commercial compiler,
try Gnu (gcc,g++,gfortran) first.
All the basic software you need (MPICH2, OpenMPI, MVAPICH2, Goto-BLAS,
ATLAS-BLAS, LAPACK, FFTW, etc) compiles with Gnu, most with very high 
performance.

Some applications also compile with Gnu, others don't.
You need to try OpenFoam and see what happens.
Some applications will compile with Gnu if you make just a few
cosmetic code changes,
often times to satisfy strict syntax requirements.
It may be a bit time consuming to find the needed changes,
but at least you can reach the goal of having the program running
within your (zero) budget.

If all fails,
then try the one-month evaluation copies of commercial compilers,
as Jonh Hearns suggested.

> ps. to the original poster - you can download one-month duration
> demonstration copies of Intel/Pathscale/Portland compilers if you want
> to see how much they can improve Openfoam performance.

I never used it, but note that there are the Sun Studio compilers also.
Somebody correct me if I am wrong, please,
but it seems to be free, at least for now:

http://developers.sun.com/sunstudio/

I hope this helps.
Gus Correa
---------------------------------------------------------------------
Gustavo Correa
Lamont-Doherty Earth Observatory - Columbia University
Palisades, NY, 10964-8000 - USA
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