Author: Rick Bischoff
Date: 08:08:04 09/22/04
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Hi,
My program has the same problem, but it wasn't null move... Even after I
disabled it I still got the Kd7 mate-- however, I had the following code in my
hash table that was a mistake:
if ( score > MATEBOUND ) { score -= (ply-1); depth=-1; }
else if ( score < -MATEBOUND ) { score += (ply-1); depth=-1; }
The idea being that a mate score is usually good for any depth-- this is
probably only true if the entry is exact and not a lower bound or upper bound..
After taking out the depth=-1 lines it finds it pretty fast.
>1. Qa1 d3 2. Qc3 e3 3. exd3 cxd3 4.Qxd3#
>
>However, Schola does not want to get this mate. I can run it as long as I like
>and it still goes for the longer mate:
>
>1. Kd7 d3 2. e3 c3 3. Qb3+ c4 4. Qb4 c2 5. Qxd6#
>
>If I disable null move it finds this very quickly. I suspect that there's a bug
>in the search somewhere though I can't find it and the traces look sane. The
>main problem is that the null move for Qa1 always cuts off so it retains Kd7
>which is the first move it considers.
>
>Has anyone else had problems with positions like these and null moves? BTW, I
>have verified null move implemented but that doesn't help either. That does make
>a small difference if I jump the position to 1. Qa1: It then finds the fastest
>mate which the regular null move still doesn't do. I've also disabled some other
>things like the hash table which sometimes get in the way for me but that didn't
>change anything.
>
>Andy.
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