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

From: Ingo Macherius
Subject: RE: [Bug-gnubg] How many threads can gnubg (reliably) handle?
Date: Sat, 12 Sep 2009 02:34:30 +0200

> -----Original Message-----
> From: Philippe Michel [mailto:address@hidden 
> Sent: Friday, September 11, 2009 11:07 PM
> To: Michael Petch
> Cc: Ingo Macherius; address@hidden
> Subject: Re: [Bug-gnubg] How many threads can gnubg (reliably) handle?
> Surely, usefulness of a larger cache depends on the number of 
> positions 
> evaluated. Maybe something like :
> 2 ply play            seconds         10k positions   cache 
> almost useless
> 2 ply analysis of match       minutes         1M              
> default size ok
> 4 ply an./short rollout       hours           100M            
> max from GUI ~ok
> long rollout          days            billions        "set 
> cache" from 
> CLI higher than GUI max useful if you have the RAM for it

Thx all benchmarkers, the picture is getting clearer, at least for me, now.

But let me repeat my request/use case. I'm using gnubg as a backend for a
match playing bot, which means I am interested in exactly one thing: Fastest
possible evaluation of a random given position by the CLI.

The cache in this use case, as Philippe writes, is "almost useless". OK,
makes sense.

However, the threading in this use case is non-existent just as well. A bot
uses the CLI version and hooks into it with either the "external" or the
"hint" command. None of the two is accelerated by threading. "external"
despite of the number of available cores uses only one of them. Didn't test
"hint", but I'm pretty sure it's the same.

It's a work partitioning thingy. As far as I understand now, thread workload
is decomposed into work batches of full or partial matches. A single move
always ends up on only one core with this approach.

Question: What effort it would be to support two thread workload
partitioning strategies, "match analysis" and "real time play"?


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