Author: Andrew Williams
Date: 05:45:51 04/23/04
Go up one level in this thread
On April 23, 2004 at 08:34:49, Matthias Gemuh wrote:
>On April 23, 2004 at 06:17:57, Andrew Williams wrote:
>
>>On April 23, 2004 at 06:01:05, Jeff GAZET wrote:
>>
>>>>>Good morning,
>>>>>i'm trying to add extensions to my engine. I'm using a classical alphabeta
>>>>>function :
>>>>>int alphabeta(int depth, int alpha, int beta)
>>>>>depth is dicreased 1 by 1 :
>>>>>eval=-alphabeta(depth-1,-beta,-alpha);
>>>>>
>>>>>At the beginning at the function alphabeta(), if king is incheck, i do
>>>>>++depth. This works fine.
>>>>>
>>>>>In the main move loop, if do a ++depth on a promoting move, juste before
>>>>>calling -alphabeta... the engine searches for ever when the first promoting
>>>>>move is found. Then, if i add "if depth<1" or <2, i don't see any
>>>>>improvment.
>>>
>>>
>>>>Maybe a stupid question, but you do remember to do depth-- after your call to
>>>>alphabeta(..)? Otherwise you could be extending *every* move in positions where
>>>>a promotion is available.
>>>
>>>Yes, depth is dicreased each call to alphabeta :
>>>eval=-alphabeta(depth-1,-beta,-alpha);
>>>
>>
>>That's not what I meant. This is what I understand you are doing:
>>
>>mv = get_next_move();
>>make_move(mv);
>>if(it_is_a_promotion_move(mv)) {
>> depth++
>>}
>>score = -alphabeta(depth-1, -beta, -alpha);
>
>if(it_was_a_promotion_move(mv)) {
> depth--; // DO YOU HAVE THIS LINE? Or am I messing it up?
>}
>
Yes, that's right. Thanks.
Andrew
>>
>>
>>
>>The last line (depth--) is VERY important. Otherwise, you're not just increasing
>>depth for mv, which is a promotion move, but also for the next move you try,
>>which could be anything. Then if you got another promotion move, you would
>>increase depth again, and you would then be searching non-promotion moves TWO
>>plies deeper than you want to. Note that because of the way you did the check
>>test, this problem doesn't apply there.
>>
>>If I've misunderstood, let me know.
>>
>>Cheers
>>
>>Andrew
>>
>>>>>I don't understand how engines like GnuChess can write : depth+=DEPTH when
>>>>>extending.
>>>>>(DEPTH is 12).
>>>>>
>>>>>Could someone give me some explanations, please ?
>>>>>
>>>>>Regards.
>>>>
>>>>Andrew
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