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

From: Philippe Michel
Subject: Re: [Bug-gnubg] How many threads can gnubg (reliably) handle?
Date: Thu, 10 Sep 2009 23:07:44 +0200 (CEST)
User-agent: Alpine 2.00 (BSF 1167 2008-08-23)

On Wed, 9 Sep 2009, Michael Petch wrote:

I find setting threads to 2 times or 3 times the core cpu count makes a
difference to help the starving issue. Curious if you see any difference. My
choice to up the thread count to 48 was not arbitrary (3 times 16). Can you
let me know if 24 threads on 16 cores does for analysis at 4 ply (and 48).

It didn't work at all. Locked after a few moves for both 24, 32 and 48 threads. 17 threads completed but a little slower than with 16.

You wrote about using more threads than cores before. It would look plausible if they could be blocked on I/Os for instance, but I don't see how it would help here, with all of then CPU-bound.

The behaviour (watched with htop) matches what Jon describes in another post. The number of active threads decreases down to one a little before the end of each game then restart at the maximum when the next game starts.

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