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Subject: Re: The need to unmake move

Author: Robert Hyatt

Date: 11:05:27 09/03/03

Go up one level in this thread


On September 03, 2003 at 13:30:26, Gian-Carlo Pascutto wrote:

>On September 03, 2003 at 13:18:49, Robert Hyatt wrote:
>
>>>Each time you get a subtree score, you must send out the score update to
>>>all processors, or store it locally and rely on remote processors to check
>>>it in your memory.
>>>
>>>Either way, you need remote accesses.
>>>
>>>Got it now?
>>>
>>>--
>>>GCP
>>
>>No, because you don't have to do that.  You _can_ ask "did my score appear
>>to change alpha/beta bounds at the split point?"  If the answer is no, you
>>do nothing.  That is the case 99% of the time.
>
>Yeah yeah, that case was implicit. The point of the thread is that it's
>not a simple matter of start thread, copy date....end thread, write data
>back. You must do some remote access always.

Yes, but the "quantity" can be limited.  IE I copy more data _to_ a thread
than I copy back when I finish the thread.

you have to make sure the search work done far outweighs the time spent in
starting/ending things.  But that is not hard to do.


>
>In the example above, you'd still need to get the next move or put yourself
>in the idle list, even though updating the score wouldn't be needed.

Getting the next move doesn't count.  Given there are 35 moves in a normal
position, even a 2 ply search beyond that move dwarfs the time needed to access
a non-local memory area to get the next move.

>
>Depending on what you do, you may want to check if alpha didn't change
>as well (not needed if you abort such trees).
>
>--
>GCP



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