Author: Robert Hyatt
Date: 06:25:20 01/16/02
Go up one level in this thread
On January 16, 2002 at 08:46:24, Derek Mauro wrote:
>On January 15, 2002 at 23:39:45, Robert Hyatt wrote:
>
>>On January 15, 2002 at 22:16:20, Derek Mauro wrote:
>>
>>>On January 15, 2002 at 21:50:52, martin fierz wrote:
>>>
>>>>aloha,
>>>>
>>>>i have a question about repetitions, and it's only about the search itself, not
>>>>about the game history: in my checkers program, to find repetition draws i keep
>>>>track of the hash keys of the current variation, and if i find that the key for
>>>>the current position has already ocurred before in the search, i return zero
>>>>without searching further. i think this is the standard implementation?!
>>>>anyway, i am wondering about the following problem: imagine you are searching a
>>>>variation, and in the end you make a repetition. the program will stop searching
>>>>there in the tree and assign the position a value of 0. now imagine that you
>>>>have a different path of moves without a repetition which ends up at that node,
>>>>probes the hashtable and returns 0. is this just my imagination, or can this
>>>>happen and can it be bad?
>>>
>>>Your hashtable should have a value in it from the first time you used the
>>>evaluation function. If the position repeats, you just have search return 0.
>>>You don't record scores in the hashtable that are the result of a repetition,
>>>you leave the original score.
>>>
>>>Derek
>>>>
>>
>>
>>
>>That leads to results just as wrong as what he described... you fail to
>>recognize draws...
>>
>If that's true than I'm doing something wrong too. Whats wrong with doing this:
>
>int search() {
> if(IsRep())
> return 0;
> if (depth == 0) {
> val = evaluate();
> recordhash(val);
> return val;
> }
> // rest of search
>}
>
>I've only been hashing scores that are the results of mates and the evaluation
>function.
>
>>
What do you do if you hash a position that will _add_ 10 more plies to the
search, but when you actually follow that branch you will encounter a forced
repetition _first_?
>>
>>>>cheers
>>>> martin
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