topic Optimization problems with x64 in Intel® Fortran Compiler

Optimization problems with x64

tant — Fri, 07 Mar 2008 19:34:51 GMT

Hi,

I am working on a large, complex simulation code. I have a case that runs badly withx64 release mode, optimization ( tried all levels including disable - which should be same as debug?), runs ok but slowly with x64 debug mode, runs ok and great with Win32 release mode. The code uses Openmp. It seems there is a problem with the x64. Could anyone give me direction as to how to resolve this?

Regards,

Thomas

Re: Optimization problems with x64

tant — Fri, 07 Mar 2008 21:58:59 GMT

Further to the previous post, I find that if I use the x64, debug mode, then turn on optimization, openmp compilation, remove debugging checks etc. to emulate the same options as release mode, the case will run as good as the win32 release mode.

What is the difference between the debug mode and the release mode?

Thanks for any insight.

Re: Optimization problems with x64

Steven_L_Intel1 — Sat, 08 Mar 2008 00:19:15 GMT

The difference is in the options used - both compile and link. My guess is that there are more options that are different. You can look at the "Command :Line" property page to see all the options in use. Check the linker too.

There really isn't enough information in your post to be able to offer any meaningful help. You don't even say what goes wrong in release mode. What you can do is try to find out which one option, which changed, causes the program to fail. Then you can determine which source file needs that option specified to fail. After that, you're on your way to narrowing down the problem.

Re: Optimization problems with x64

TimP — Sat, 08 Mar 2008 01:36:00 GMT

You may have arrived at a good set of optimizations. If your application doesn't benefit from inter-procedural optimizations, taking the debug options and changing from -Od to -O2, perhaps suppressing debug symbols, may be close to an optimum solution.