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Subject: Re: Parallel search algorithms

Author: Frank Schneider

Date: 09:37:34 08/30/01

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On August 30, 2001 at 09:59:57, Robert Hyatt wrote:

>On August 30, 2001 at 05:58:01, Dan Andersson wrote:
>
>>One really simple parallel search algorithm is to have two searches working
>>independently. Only one search communicate with the output. But both share the
>>same hash table and thus work together. If you are lucky, that can result in a
>>good speedup. To increase the efficience of this algorithm, use ETC to get
>>better use of the hash table, this won't strain bandwidth in the bulk of the
>>search.
>>
>>MvH Dan Andersson
>
>
>I don't see how this will perform reasonably when it is probable that both
>processors will search the same tree at the same time,

The idea is to detect all-nodes and let n-1 processors search the moves
in a different (e.g. random) order.

However, didn't work too well for Gromit so far :-(

Frank

> and hashing won't stop
>that from happening.  This might be better than nothing.  As might the ABBADA
>idea, but good old intentionally deliberate parallel searching has to be
>better than these "uncoordinated approaches".
>
>The shared hash table with the "exclusive bit" is a big problem on most
>machines.  Locking hash entries is a performance killer, and they have to be
>locked if such a bit is used.



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