[computer-go] Library of Effective GO routines v 0.106

[Łukasz Lew]

On 2/22/07, Sylvain Gelly <sylvain.gelly at m4x.org> wrote:
> Hello,
>
> > I do not understand it. Maybe someone does?
> > I've made some tests on 2 core processors, and I have strange results.
> > Some of 2 core processors got results exactly 2x times worse than they should.
> > Why?
> > I have no idea.
> > But 2.8 Ghz 2 core works exactly like my 1.4 laptop.
> > Also version of g++ does matter.
>
> Here, from my experience, the following can matter a lot:
> - version of g++ (g++ 4.1 gave me +50% against g++ 4.0 on an opteron!)

True.

> - version of the libc: even compiled with a modern compiler, a program
> running on a machine with an old version of the libc can be very
> significantly slower (-30% observed!).

True.

> - exact version of the processor: today the frequency means nothing,
> nor the name of the processor. You have to check the exact numbers.
> And I also observed that even the small numbers as the "stepping
> number", matters. MoGo runs faster on my P4 3.4 Ghz  than on a 3 years
> newer P4 3.8 Ghz, which has also more cache. I ran test on other P4,
> and the slower had a different stepping, that's all (all are dell
> computers using same hardware).
> - Measure of time: if you take the CPU time, on multiprocessor
> machine, while using multithreading, sometimes the reported time is
> not what you expect (generaly reported for all the threads), so when
> you calculate the speed of playouts, you can have a 2x/4x factor.
>
> Hope that can help,

Thanks for information.


I used a static binary compiled in one place with good compiler.
I do not use threads, nor external libraries (in benchmark).
I checked exact stepping in /proc/cpuinfo

So I still have no idea :)

Łukasz

> Sylvain
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