Author: Robert Hyatt
Date: 11:25:41 01/14/98
Go up one level in this thread
On January 14, 1998 at 08:49:27, Dan Homan wrote: >On January 13, 1998 at 14:43:16, Robert Hyatt wrote: > >>On January 13, 1998 at 09:08:49, Dan Homan wrote: >>> >>>p.s. My program does >>> >>>capture extensions (4/10 of a ply) >> >>dangerous one there. Ken Thompson used 1/2 ply in 1983, and probably >>lost the 1983 World Championship as a result of doing this. He reported >>it helped his WAC results quite a bit, but it costs about 1/2 to 1 ply. >>He later discarded it totally. >> >> >>>re-capture extensions (1 ply) >>>check extensions (1 ply) >>>pawn push extensions (1/2 ply or 1/3 ply) (endgame and late >>>middle-game) >>>bruce's mate ext. (1 ply) >> >>All reasonable. I am now using 3/4 ply for *everything* in Crafty, but >>do allow multiple extensions to add together, with a limit of 1 ply. >>This >>actually improved the WAC results and seems to be running a good bit >>faster >>to reach the same depth... > >You said you allowed multiple extensions to add together with a limit of >1 ply. I assume this means that you do not allow left over fractions to >roll over to the next ply. your wording makes it hard to answer... but here goes: At every ply along the way, depth gets reduced by 1 ply, as you would expect. At every ply along the way the depth gets incremented by fractional values that can not exceed one ply. So if ply 3 increments by 3/4, and ply 4 increments by 1, that 3/4 is *not* lost because it came from a different ply. I only restrict a single ply to adding in no more than a one ply extension... but it passes along everything it inherits from prior plies. So a 3/4 extension at ply=1 gets carried along with no real effect on the search until someone further along adds in at least 1/4 more. Since all of my extensions are currently 3/4, the first 3/4 doesn't do much (this is a lie, more later) but the second 3/4 rolls this up to 1.5 plies which extends every line below this by 1 ply. And the extra 1/2 is kept since it didn't come from the current ply, so that the next 3/4 ply will also extend by one, as will the next (but not the 4th). I said the above is a lie because my initial search depth for a 1 ply search is set to 1.75, so that the first 3/4 ply search extension does something, as does the 2nd and 3rd. but the 4th won't, but then we start over again with the 5th, 6th and 7th extending but the 8th not. > >I tried eliminating the capture extension, it reduces my search tree >by a factor of 2 in most positions so I get about 1 ply deeper in the >same time. I solve some of the WAC positions a ply later, but the >speedup generalizes to all positions. I ran overnight with the new >version on FICS, and it doesn't seem any worse (it even gained 20 >rating points). > >I'll probably write some analysis tools like Bruce suggested to get >a more concrete measure of the change, but I am happy with a smaller >search tree. :) > > - Dan
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