Author: Dezhi Zhao
Date: 14:11:30 12/04/02
Go up one level in this thread
On December 04, 2002 at 09:09:21, scott farrell wrote:
>On December 03, 2002 at 15:51:53, Dezhi Zhao wrote:
>
>>On December 03, 2002 at 04:26:50, scott farrell wrote:
>>
>>>I choose to start the story now ...
>>>
>>>A few months ago I added code to show "mate in 4" rather than just mate. It uses
>>>mate-depthTree in order to document the mate depth.
>>>
>>>This helped alot in actually mating opponents, as it can choose the shortest
>>>route to mate. rather than as it was just doing lots of checks, that all lead to
>>>mate, and randomly actually mating the opponent.
>>>
>>>This worked well, EXCEPT, in deep checking lines, it actually fails slower, as
>>>it tries to look for a better mate. So it actually blew nodes out somewhat on
>>>some test positions.
>>>
>>>I still go a few more plies during iterative deepening to try to find shorter
>>>mates - due to null move and pruning etc. But these searches seem to be slow
>>>also.
>>>
>>>I recently added a nice piece of code:
>>>
>>>if (alpha>INFINITY/2){
>>> matein= INFINTY-alpha; //or whatever you use to calc mate depth in plies
>>> if (depthTree>matein)
>>> return alpha;
>>>}
>>>
>>>Do others think this is valid? fail low if you are already too deep, and just
>>>fail low.
>>>
>>>It sure verifies the mates about 1000 times faster.
>>
>>This does cause some problems. You could notice the problem of producing longer
>>than necessary mate sequence if you test more positions.
>>Worse than that, sometimes your modification may cost much more nodes in some
>>positions. Your trick sounds logical at first sight. However, you must take
>>transposition into account, which makes the seemingly futile search productive
>>instead sometimes. I realized this when I played with such idea 2 or 3 years
>>ago.
>
>mmmm ... good thinking .... transpositions ..... if you disregard my pruning, is
>INIFINITY-depth accurate when you take into account transpositions? I think not,
>as the same position, may be achieved through a shorter or longer route.
>
>Do you have a solution to this?
>
>Scott
Your idea should work if you could live without a transposition table. I dont
have a neat solution to it. After playing it with frustrations, I discarded it
for the sake of simplicity. I think you might find a practical solution to it.
However I doubt if the additional checking or exception handling will offset the
saving.
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