Author: Dan Newman
Date: 13:16:54 02/12/02
Go up one level in this thread
On February 12, 2002 at 10:55:09, Miguel A. Ballicora wrote:
>On February 11, 2002 at 19:21:18, Ralf Elvsén wrote:
>
>>On February 10, 2002 at 19:49:01, Miguel A. Ballicora wrote:
>>
>>>I never understood what the people is doing with the mate values, I always
>>>get confused. I am glad that I came up with my own approach before I asked or
>>>saw any post about it. :-)
>>>
>>>What I do in pseudo code in Gaviota is
>>>
>>>search (alpha, beta)
>>>{
>>> adjust_in (&alpha, &beta); /* increments alpha += 1 and beta += 1 if they
>>> are positive mate values, do the opposite if
>>> it is a negative mate value */
>>> probe_hashtables_normally()
>>>
>>> loop { /* normal alpha beta stuff */
>>> makemove();
>>> value = search_moves_for_best_value(-beta, -alpha);
>>> unmakemove();
>>> best = keep the best value;
>>> }
>>>
>>> store_in_hashtables_normally();
>>>
>>> adjust_out(&best); /* decrement best -= 1 if it is a +mate value
>>> increment +=1 if it is a -mate value */
>>> return best;
>>>
>>>}
>>>
>>>And basically, I do not do anything else. I store in the hashtables without
>>>any change. adjust_out() it is used too when I return early.
>>>
>>>Regards,
>>>Miguel
>>
>>Here's another one who is doing the same thing :) It is really
>>simple and clear. My functions are called "upstep" and "downstep" :)
>>
>>Ralf
>
>Good! Then I am not crazy. At least I am not alone in the nuthouse. :-)
>
>Regards,
>Miguel
I tried something like this in Shrike last year, but ran into trouble.
The idea I had was to have the mate-in-n scores at a node really mean
mate-in-n from that node. Then, I thought, I could just store the
scores without adjustment in the hash table. (And it made more
sense to me as well.)
I also realized that alpha and beta mate-in-n scores needed to be
adjusted too. That is (I think) where I had the trouble. I ended
up with bound scores that were oustide the [-32768,+32767] range
that is allowable in my program. This caused my hash table
entries to become corrupted (since I stuff the score into half
a 32-bit word by first adding 32768 to it and then ORing the
result in). The out-of-range error happens because a mate-in-n
bound can end up being incremented more than n times.
Anyway, I gave up and put things back the way they were. After
seeing that others have done this successfully I think I'll have
to try it again...
-Dan.
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