Author: Sune Fischer
Date: 13:02:45 06/18/02
Go up one level in this thread
On June 18, 2002 at 12:11:57, Robert Hyatt wrote:
>
>OK... define "MATE" as 32768, for now.
>
>If you find a move at the root that leads to a mate in 4, the score
>will typically be 32768 - 8 since you find you are mated at ply=8 and
>you return MATE-ply (I do, anyway). Therefore, the root score that
>gets backed up will be 32760, and so far, all is well. That means that
>the "mate score" that gets returned from ply = 8 has to be - ( MATE - PLY )
>so that - is bad for the side on move at ply=8.
>
>Note that you have 4 moves for the program in the path, the move at
>ply=1, 3, 5 and 7. When you store a hash table entry at ply=7, you
>should store MATE-1, since the move at ply 7 will result in a MATE at
>ply=8. At ply 5, you should store MATE-3, at ply 3 you should store MATE-5
>and if you want to store the entry at the root, it would be MATE-7.
>
>All this means is that at any point in the path that terminates in a mate
>score of any kind, you have to adjust the score so that it is a mate-in-N
>from the current ply, not from the root. Because the root score is wrong
>at the current ply, since we are _closer_ to the final mate than we were at
>the root of the search.
>
>If that isn't clear enough, ask again. You can find how I return a mate score
>by looking at the bottom of search.c in Crafty (look for string MATE). You can
>find how I adjust the mate score before I store it in the hash table by looking
>at hash.c, module Store()...
>
>Bob
I think that _is_ what I'm doing!?
#define CHECKMATE 100000
#define CMSCORE 99000
search() {
..
if (!movesfound) {
if (InCheck(wtm))
score=-CHECKMATE+depthroot;
else
score=DRAWSCORE;
}
...
}
hasprobe() {
...
switch (phash->flag) {
case HASH_EXACT:
if (abs(score)>CMSCORE){
if (score>0)
score-=depthroot;
else
score+=depthroot;
}
...
}
hashstore() {
...
if (abs(score)>CMSCORE){
if (score>0)
score+=depthroot;
else
score-=depthroot;
}
...
}
"depthroot" is just distance to the root position we are searching, I assume it
is identical to yours "ply" variable.
Something must be wrong, I get weird results, it does work fine, it seems, but
when I look at the log I'm worried.
This position was from a quick test game, it's mate in 3, but I get mate in 1
three times in a row, but it doesn't have a problem playing the right moves,
really strange...
[D]1r2qrk1/n5p1/1p1p2P1/p2p2P1/2P1pPK1/P1PB2P1/2Q5/1R5R w - - 0 1
-S.
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