Author: Steffen Jakob
Date: 13:50:09 12/08/03
Go up one level in this thread
On December 08, 2003 at 16:19:48, Tim Foden wrote:
>On December 08, 2003 at 11:02:22, Alvaro Jose Povoa Cardoso wrote:
>
>>
>>I've been thinking about the efficiency of the history heuristic at high search
>>depths.
>>It seems to me that the history table will be overwritten many times if we have
>>a search of several billions of nodes. Additionally, as the search moves to
>>different parts of the tree the history table values will be somewhat trashed.
>>What do you think we could do about this?
>>Maybe limit the history heuristic to a certain depth (ex: the nominal depth).
>>
>>Comments anyone?
Hi Tim!
I hope you enjoyed your trip back to spain. :-)
>What happens in GLC is whenever it increments a value in the history table it
>checks it against a maximum. If the maximum value is exceeded, it divides all
>values in the table by 2.
I do almost the same! I don´t modify the values in the table but remember a
shift value which is used to reduce the history values on demand:
int historyShift = 0;
inline Value getLimitedHistoryValue(Value historyValue) {
Value limitedValue = historyValue >> historyShift;
if (limitedValue > MAX_HISTORY_VALUE) {
historyShift++;
limitedValue = limitedValue >> 1;
}
return limitedValue;
}
In the past I didn´t limit the history value. Then I realized that it became a
dominant sort criterium in deep searches which was of course very bad.
Best wishes,
Steffen.
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