[AMBER-Developers] SSE2 / SSE3 settings no longer used for ifort?

From: Ross Walker <ross.rosswalker.co.uk>
Date: Fri, 23 Oct 2009 16:45:19 -0700

Hi All,

It seems that the config.h prepared by ./configure is no longer setting the
SSE2 / SSE3 optimization flags for the Intel compiler. This can reduce
performance by >30% in some cases. Does anyone know why this was turned off?

Specifically this is things like:

ifort -axWPS

The problem is that different versions of the Intel compilers use different
sets of flags. Once again an example of the patients running the asylum.
However, we could set -fast as the default option which would turn on:

-xP -O3 -ipo

The ipo is a problem since it means all the optimization is done at link
stage and you lose all the benefits of parallel builds and each new make is
very expensive. We could specify


but a lot of this is now changed and deprecated in ifort >11.0

Hence should we have an intel9 and intel10 target which uses -O3 -ip -axWPS
and an Intel11 target which uses -O3 -ip -axSSE4.2,SSE4.1,SSSE3,SSE3,SSE2


All the best

|\oss Walker

| Assistant Research Professor |
| San Diego Supercomputer Center |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
| http://www.rosswalker.co.uk | PGP Key available on request |

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Received on Fri Oct 23 2009 - 17:00:02 PDT
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