topic gfortran -O3 in Intel® Fortran Compiler

gfortran -O3

yuwb — Mon, 22 Nov 2010 21:26:19 GMT

I have a code complied using gfortran -O3. I currently evaluating Intel Visual Fortran. What will be the equivalent flags to gfortran -O3?I the project properties, Iused Maximize Speed plus Higher Level Optimizations (/O3), however the code compiled by IVF is about 2-3 time slowers? Any suggestions?

gfortran -O3

Steven_L_Intel1 — Mon, 22 Nov 2010 21:41:35 GMT

Can you show us the code? Sometimes there are differences not related to optimization (such as the size of I/O records).

gfortran -O3

Steven_L_Intel1 — Tue, 23 Nov 2010 01:54:13 GMT

I suggest viewing this to see an overview of the VS environment.

Do you have any OPEN statements with RECL= keywords?

gfortran -O3

yuwb — Tue, 23 Nov 2010 13:32:47 GMT

I only count the time without I/O statements as my I/O are localized in the very beginning and at the very end.

gfortran -O3

Steven_L_Intel1 — Tue, 23 Nov 2010 16:24:45 GMT

Try using -fast and see what it does for you.

gfortran -O3

yuwb — Tue, 23 Nov 2010 20:21:08 GMT

Thanks Steve for your help. However, how to activate this option through MS Visual Studio 2010?

gfortran -O3

Steven_L_Intel1 — Tue, 23 Nov 2010 20:40:25 GMT

There is not a property for that. I did not realize you were using Visual Studio.

Let me suggest the following property settings:

Optimization > Optimization > O3
Optimization > Interprocedural Optimization > Multifile
Code Generation > Intel Processor-Specific Optimization > /QxHost
Floating Point > Floating Point Model > Fast=2

gfortran -O3

yuwb — Tue, 23 Nov 2010 21:21:43 GMT

I did as you suggested, the code runs for 866.031. Using gfortran, it runs for 438.328.

gfortran -O3

Steven_L_Intel1 — Tue, 23 Nov 2010 21:56:55 GMT

Something is very wrong, but it's impossible to say what without seeing the code.

gfortran -O3

yuwb — Tue, 23 Nov 2010 23:46:30 GMT

Can you give me your email address for me to send you the code? I don't want to share it on the forum.

gfortran -O3

Steven_L_Intel1 — Wed, 24 Nov 2010 00:48:11 GMT

You can provide it securely through Intel Premier Support. Please ask that the issue be assigned to Steve Lionel.