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Subject: Re: How to make your movegen 4x slower in 1 easy step

Author: Vincent Diepeveen

Date: 06:06:42 08/31/01

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On August 30, 2001 at 23:21:58, Robert Hyatt wrote:

>On August 30, 2001 at 20:48:30, Vincent Diepeveen wrote:
>
>>On August 30, 2001 at 14:43:00, Robert Hyatt wrote:
>>
>>>On August 30, 2001 at 14:25:39, Scott Gasch wrote:
>>>
>>>>On August 30, 2001 at 14:07:50, Dann Corbit wrote:
>>>>
>>>>>
>>>>>Dumb question:
>>>>>Why not let them all have their own move generator and just share the hash
>>>>>table?
>>>>
>>>>I guess that's one approach -- run them as seperate processes in seperate
>>>>virtual address spaces and simply share the hash table.  I was planning on using
>>>>simple threads in the same address space though.  Not sure why, seems more
>>>>straightforward to me...
>>>
>>>
>>>One reason is that there are other things to share.  Killer moves.  History
>>>move counts.  move lists (you need to share a move list at a ply where more
>>>than one processor is searching) and so forth...
>>
>>No you don't want to share killer moves. History moves do not give
>>a speedup if you write a bunch of extra rules to order moves.
>
>Sure you do, if you do it right.  I share them.  And history moves are better
>than random, and work fine for everyone that has tried them.

You don't want to share killermoves, as each processor searches its
own tree, though there might be transpositions, the most important thing
are the killermoves which gets updated each time. The second killer in
my killermove list is hardly of any statistical significance in DIEP.

So a killer which kills this line is interesting.

Suppose now that in parallel 2 processes are writing into a killer list,
both having a complete different position at their board, that's quite
silly isn't it?

>There's dozens of things that need to be shared.  I can dump my shared structure
>here if needed to show what I share.
>
>It is pretty large however.



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