64 bit Windows AMD64/EM64T Compatibility.

[Dan_W_]

Can the 64 bit EM64T Intel Fortran Compiler generate code which is 100% compatible with the AMD64 Opteron/Athlon64 for running on 64 bit Windows?

If not, this is really bad because you need two separate compiles, one for AMD64 and one for EM64T.

Dan.

[TimP]

Yes, the code generated by either the default (no architecture specified, no vectorization), or by use of the -QxW or -QaxP vectorizing options, is fully compatible with AMD64. Only the -QxP option should cause it to fail to run on AMD.
I have heard of Ifort compiled code which would run OK on all AMD64 desktops, but not on an AMD64 laptop. As far as I know, no one has submitted documentation which would help diagnose the issue. That's a probable reason for the legalese in the platform requirements list; it is not possible to test for undocumented differences in all platforms.
To some extent, different switches and directives will optimize performance on the different architectures. You may need separate compiles if you require within 5% of maximum performance on both architectures, depending on your application. The same could apply across the range of 64-bit Xeon platforms, from Pentium D to 4-way platforms. Don't know if that was your question.

[Dan_W_]

Thanks Tim.

Maximum performance on both hardware types is not a concern for me.

My experience with our software has been that using special optimisations just creates more problems that it's worth. i.e performance is only modestly increased at the expense of reduced stablility (code no longer runs on some cases when compiled with more agressive optimisations).

My main concern is generating a 64 bit executable that will reliably run on both hardware types on 64 bit Windows.

Hopefully things will be fine when we make our 64 bit Windows port this year.

Dan.

[Steven_L_Intel1]

The processor options we recommend for that are -QxW -QaxP. Use these two together.