Re: What optimizaton flags should i use (g++-4.3.3,Linux,Core2Duo)?

[Matthew Lai <cyberfish@wecheer.com>]

4.3.3 has
-march=core2


Tim Prince wrote:
> Martin Ettl wrote:
>
>   
>> i am playing around with g++-4.3.3 on Ubuntu Linux. The project i am working does a lot of floating point arithmetic (based on double variables). The testplattform i use, is a intel core 2 duo processor. So what optimization flags are good for this plattform? Currently i am using -O3 -funroll-loops, but there are a plenty other. 
>>
>>     
> If you are using the 64-bit compiler, this may be sufficient, but
> --param max-unrolled-insns=<your choice>
> or
> --param max-unroll-times=4
> may be useful to make the unrolling less aggressive.
>
> I suppose you're not using the 32-bit compiler, where you would set
> -march=pentium-m
> or
> -march=prescott
> or some other option, to enable partial or full use of sse2.
>
> Add -msse3 if you like (either 32- or 64-bit), but you probably have no
> use for it.
>
> -fassociative-math (or, if it doesn't work, -ffast-math) are required for
> vectorization of sum reductions.  Otherwise, they may be undesirable.
> They are saner in gfortran than in g++.
>
> If you use OpenMP, of course you would set -fopenmp.
>