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Re: [Bug-gnubg] How many threads can gnubg (reliably) handle?

From: Jonathan Kinsey
Subject: Re: [Bug-gnubg] How many threads can gnubg (reliably) handle?
Date: Thu, 10 Sep 2009 09:55:38 +0000

Philippe Michel wrote:
> On the other hand, analysis doesn't seem to scale well above 8 threads.
> It looks like moves are analysed one by one and after the opening and
> early middle game, even with a large move filter, some, then most of the
> threads are starved. 8 threads was about 7 times faster than 1, but 16
> threads was merely 9 times faster.

This is almost definitely caused by the fact that I wrote the code to analyse
each game separately, i.e. all the moves in one game are dished out and then
waited for before the next game is analysed. This means that towards to end of
each game lots of threads will wait for the last moves to finish.

The answer would be to split out all the moves of the entire match in one go,
shouldn't be too hard as long as it doesn't break anything. This would be
worthwhile as it would speed up things slightly even for small numbers of cores.


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