[Omp] OpenMP with different compilers

[Chunhua Liao]

How did you measure the speedup? 

As far as I know. Intel compilers already use -O2 as default to compile your
sequential programs and usually get very good performance.  

You might need to turn off the Intel compiler optimizations to see the sole
effect of OpenMP.
 

-----Original Message-----
From: Omp-bounces at openmp.org [mailto:Omp-bounces at openmp.org] On Behalf Of
Xiao Dong
Sent: Friday, April 01, 2005 2:06 PM
To: Omp at openmp.org
Subject: [Omp] OpenMP with different compilers

Good day,

I've been working on a Monte Carlo code paralleled with OpenMP. 
Compiling it with pgf90 simply gives a vergy good speed up of 2.0 on dual
processor AMD Opteron server; compiling it with xlf90_r somehow gives a
speed up of 1.3 on dual processor G5 server; while compiling it with ifort,
the worst thing happens - the speed up is 0.5 running with 2 threads on SGI
Altix (8-Itanium2).  What could be the problem? 
Supposedly, I've set the right environments on the Altix

KMP_STACKSIZE=1g
OMP_DYNAMIC=FALSE
KMP_LIBRARY=turnaround
OMP_NUM_THREADS=2


Tnanks for your comments!

Regards,

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