Author: Robert Hyatt
Date: 03:48:06 08/03/98
Go up one level in this thread
On August 03, 1998 at 03:14:03, Ernst A. Heinz wrote: >On August 03, 1998 at 02:21:12, Amir Ban wrote: >> >>I always accept the fail-high move immediately. >> >>There are parameters that you are important that you don't mention: What size >>window is used during normal search ? If it's zero-width, or very small, then >>fail-high doesn't mean it's much better than the previous best, and you can take >>the new move or leave it. If you use a 0.3-0.5 window, as I do, fail-high means >>it's clearly better than the previous, even it later fails low. >> >>Also, what window do you use on the re-search that fails low ? If you use >>new-alpha+1 to infinity, then maybe the fail-low happened because the value is >>exactly new-alpha. If you use a window of old-alpha to infinity, then a >fail-low >>indeed makes the move suspicious. >> >>Amir > >Good point, Amir! > >Actually, I do not recall to having encountered the fail-low after fail-high >behaviour as long as the research is done with the *old alpha*, i.e. the >same that was used when the fail-high occured. > >Otherwise, this nasty fail-low after fail-high behaviour unfortunately >seems to occur quite frequently. > >=Ernst= This is a known problem will null-movers... if you use the old alpha, you may not get the fail low, but you will get a score lower than the previous best move, which might be just as ugly...
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