Author: Peter Fendrich
Date: 08:46:29 01/18/00
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On January 17, 2000 at 10:54:53, Bas Hamstra wrote: >It should work. I used this a while ago with ab (in stead of PVS) and it didn't >give any problems. I don't see why it wouldn't work with PVS. 3L raises Alpha >and 3U decreases Beta. If you get a fail high on that window there is a search >inconsistency. An earlier search said "v can't be higher than X" and then >research returns v > X. Does it still occur with nullmove turned off? Nullmove >causes search inconsistencies, which is normal. A different ab window lets >nullmove prune different branches. > > >Regards, >Bas Hamstra. It should work, but it doesn't! I'm trying to find out what the problem is, still without any success. I have a big log-file to wade through. Nullmove is not the problem but I have changed a lot of code lately so... Vincent and Ernst had some ideas that I haven't tried yet. //Peter >On January 17, 2000 at 10:23:13, Peter Fendrich wrote: > >>When searching the hash table, I've detected basicly 9 different states. >>The value from the table is a Lower (L) or Upper (U) bound or Inside (I) it's >>A/B-window. >>For each of these we have 3 cases: >>1. value <= current Alpha >>2. value >= current Beta >>3. current Alpha < value < current Beta >> >>Combining it all we have: 1L, 1U, 1I, 2L, 2U, 2I, 3L, 3U and 3I >> >>For now I'm interested in case and 3U. >>When we have 3L, we know that the table entry is the lowest >>possible value and that the current Alpha is lower. To me it seems >>reasonable to set current Alpha = table value. >>For 3L this will be: current Beta = table value. >> >>That doesn't work well with my program which has a PVS-based alg. >>When re-searching a move, the A/B-window will be narrowed down in >>the tree based on the 3L and 3U cases above and a FailHigh together with >>a cut PV-line will be the result. >>I have tried to set current Alpha = value-1 and current Beta = value+1 >>with a somewhat better result but this doesn't "feel" right! >> >>Now I've turned the thing off completely and can sleep at night again... >> >>Something is wrong here. >>Comments please! >> >>//Peter
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