[MITgcm-devel] compiler optimization on SunOS

[Dimitris Menemenlis]

> I guess that depends on the compiler, right?

Yes, the results I quoted were for ifort on an altix using propack 5 but the 
general lesson is probably valid for other compilers too, that is, if speed 
matters we cannot cannot assume that higher optimization levels are always 
faster.  Details attached for MITgcm-devel reference:

> I did these timings on a development system with no one else running on
> the machine. The operating system is propack 5 that is not yet ready for
> prime time including lack of a working CXFS. In effect I had a dedicated
> system to run on. The optimizer has no clue about the operating system or
> the filesystem, so I expect the results to be reproducible. That said, we
> all know how large timing variations have been, and my version doesn't
> include Ken's contribution to speeding up the code.