topic Re: /QaxW versus /QaxN in Intel® Fortran Compiler

/QaxW versus /QaxN

Ilie__Daniel — Mon, 14 Jan 2008 12:21:58 GMT

Hello!

Could anybody tell me what is the difference between /QaxW and /QaxN options?

The documentation states the following:

for /QaxW: Can generate specialized code paths for SSE2 and SSE instructions for Intel processors, and it can optimize for Intel Pentium 4 processors and Intel Xeon processors with SSE2.
for /QaxN: Can generate specialized code paths for SSE2 and SSE instructions for Intel processors, and it can optimize for Pentium 4 processors and Intel Xeon processors with SSE2.

Thank you for your time.

Kind regards,

Daniel.

Re: /QaxW versus /QaxN

TimP — Mon, 14 Jan 2008 14:13:56 GMT

As Steve pointed out, there is a possibility /QaxN will produce better optimized code in the SSE2 path for Intel CPUs. If you want to run exclusively on CPUs which support SSE2, including AMD CPUs, you would prefer /QxW. For running exclusively on SSE3, if you see an advantage in including SSE3 instructions, you could use /QxO.

Re: /QaxW versus /QaxN

Steven_L_Intel1 — Mon, 14 Jan 2008 15:47:07 GMT

Tim, I don't believe that to be the case. As far as I know, AMD processors will always take the "generic" path when a /Qax option is used. You can set this generic path to be SSE2 by also using /QxW, or SSE3 with /QxO.

The difference between W and N is that N requires Intel CPUs and enables some additional optimzations. There's no point in using /QaxW - you may as well use /QaxN.