Hi everyone,
I did not remove the flags, but willing to comment anyway.
I would delegate the choice of compiler/flags/libraries/features/whatever
to the user; for example, through environment, like AMBER_F90,
AMBER_F90_OPTFFLAGS, etc; configure would then pick up these
and create config.x (.h, that is not really a header, looks quite
amusing, IMHO.) There should also be a README file around
(or a webpage, or whatever), that summarizes useful combinations
of various flags, compilers, etc. In other words, the role of
configure would be to (a) check whether the specified combination
of flags/compilers/libraries works and (b) create the 'config.x'. This
way, IMHO, both configure & co and user experience would be simpler.
With kind regards,
Volodymyr
On Fri, October 23, 2009 19:45, Ross Walker wrote:
> 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
>
> -axWPS
>
> 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
>
> Comments?
>
> All the best
> Ross
>
> /\
> \/
> |\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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>
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>
>
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Received on Fri Oct 23 2009 - 17:30:03 PDT
