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Subject: Re: late move reductions (and another question)

Author: Tord Romstad

Date: 10:05:18 03/03/06

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On March 03, 2006 at 12:20:43, Tony Werten wrote:

>On March 03, 2006 at 09:46:12, Tord Romstad wrote:
>
>>What's the problem with a shared history table?
>
>Problem is a big word, it probably isn't that bad.
>
>Suppose thread 1 want to add 1 to the counter:
>1) load memory into register
>2) add 1 to register
>3) move register to memory
>
>If the thread is interrupted between 1 and 3 and thread 2 adds to the same
>entry, you have lost 1 add.

Yes, this can happen, of course, but it doesn't bother me at all.
Who cares if the history counters are only approximately correct?
The deviations will be really tiny, and I would be very suprised if
they have any measurable impact on move ordering at all.  I really
don't understand why anybody would want to copy the entire history
table to each thread at all split points, instead of just sharing it.

Tord



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