Author: José Carlos
Date: 02:14:39 04/14/04
Go up one level in this thread
On April 14, 2004 at 03:32:17, Peter Fendrich wrote: >On April 14, 2004 at 02:21:41, Christophe Theron wrote: > >>On April 14, 2004 at 00:26:34, Eric Oldre wrote: >> >>>After you find the 1st "good" move don't you narrow the alpha beta window so >>>that you don't know how much worse the 2nd move is, only that it is not as good >>>as alpha? >>> >>>Or do you not narrow the window at the root node? that seems like it would >>>greatly expand your search tree. >>> >>>or am i missing something else? >>> >>> >>>On April 14, 2004 at 00:09:24, Robert Hyatt wrote: >>> >>>>Simple idea: >>>> >>>>a move is "easy" and can be made after using less than the planned time limit if >>>>and only if >>>> >>>>1. estimated score for first root move is way higher than the second move. IE >>>>say 2.00 better. >>>> >>>>2. This is a recapture. IE opponent just captured a piece of ours and we are >>>>recapturing on the same square. >>>> >>>>Other types of "easy" moves have higher risk to stop the search early... >>>> >>>> >>>>> >>>>>Thanks, >>>>>Eric Oldre (new chess programmer) >> >> >> >>I think that by "estimated score", Bob means the score returned by a SEE (Static >>Exchange Evaluator), not by a real search. > >I shouldn't tell what Bob means but I doubt this is right... >I wouldn't rely on a SEE for such decisions when the first few iterations will >give you a much more reliable score quite fast and you could use the score for >previous move in the game as a staring point. >If the score fulfills the conditions mentioned by Bob from the first iteration >and up to lets say 1/2 the total time alotted for that move then stop and make >the move. (Given that the time allocated for a move is just a function of >remaining time and number of moves left) >/Peter Hi Peter. Remember that you need an open window to compare score. As most programs use null windows for non pv nodes, you can't use the scores of the first iterations, unles you want to avoid PVS until iteration n. I use a QSearch with (-inf,+inf) window for all nodes at the root before starting iterative deepening. If I find a "singular" move there (meaning clearly better than all others) and this is the move stored in the hash table for the root position, I flag it as "probably easy move". Then I start iterative deepening. If, at some point, a non pv move fails high at the root, I remove the flag. Otherwise, after 1/10 of the allocated time, when I finish searching the current iteration at the root, I check if the PV move is equal to the "probably easy move". If so, I make that move. José C.
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