Author: blass uri
Date: 03:03:55 05/16/98
Go up one level in this thread
On May 15, 1998 at 18:26:47, Edward Screven wrote: >On May 15, 1998 at 05:56:35, Harald Faber wrote: > >>AFAIK it is because the programs also profit from the permanent brain. >>So if the program makes a forced move at depth=3 it may consider a >>really bad move to be played next by the opponent and wastes time >>finding the best answer to that move. So it is more senseful to let a >>program think a little longer so that the chance is higher to see the >>opponent's next move. > >having a better guess for "permanent brain" searching helps make >the time spent searching for a forced move a little less wasted, >but i don't think it's the reason why it happens -- certainly not >for my own program. > >the real problem is how sure do you want to be that the obvious >move is actually forced? if you spend too little time searching >it what looks like a forced position, you might miss a good >not-so-obvious move, or you might not see that capturing that >pawn leads to dropping a piece. > >my approach to this is to use the notion of singularity to decide >if a move is forced when replying to a check, capture, or >promotion. basically, on the first iteration after searching >at least 1/12 of the time i would otherwise allocate, i try to >prove that all non-pv moves are more than some threshold worse >than the pv move. if the answer is affirmative, then i search >the pv one ply deeper. if i don't fall off of a cliff, then i >end the search. I do not understand why to waste at least 1/12 of the time... if the second best move give the opponent the possibility to do checkmate. usually this is not the case but you do not waste a lot of time to identify cases like that if you only check the possibility to do mate in 1 or 2(less than 0.1 second per move). and in the average you save time. > >this has proven relatively safe, and often does save time. >before i added the "cliff" check i saved more time, but i >also found a few cases of cutting searches short too soon, >with disasterous results. > >it's not too expensive, because if the steps of the proof >are similar to normal root search steps, so proof failures >leave the root search close to where it would have been >anyway. > > - edward
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