Author: Anthony Cozzie
Date: 07:23:20 12/17/03
Go up one level in this thread
On December 17, 2003 at 09:49:12, Andrew Williams wrote: >On December 17, 2003 at 07:48:55, Anthony Cozzie wrote: > >>On December 17, 2003 at 02:12:08, Andrew Williams wrote: >> >>>On December 16, 2003 at 21:22:56, Anthony Cozzie wrote: >>> >>>>Recently I experimented with adding MTD(F) into Zappa. It has been an >>>>interesting experiment, but I am going back to PVS(). >>>> >>>>I thought that since Zappa has a [UL,LL] paired transposition table and an >>>>evaluation granularity of only 1/100 of a pawn, MTD(f) would work quite well, >>>>but that does not seem to be the case. The MTD(f) version of Zappa does >>>>slightly better on test suites (113/183 @ecmgcp v 106 @ 10s/move) but in the >>>>positional test suites it averaged about 3/4 of a ply less than the PVS() >>>>version. My guess is that because MTD(F) tries all moves, some of the >>>>"ridiculously losing captures" ordered near the end by PVS() are tried earlier, >>>>which accounts for the increased test suite performance. >>>> >>> >>>I don't understand the last part of this paragraph. Why would "ridiculously >>>losing captures" be tried earlier (than what?) in MTD? >>> >>>>If anyone has any suggestions, I'm keeping the MTD(F) code in Zappa (just turned >>>>off) and I'm willing to try anything. >>>> >>>>anthony >>> >>>Andrew >> >> >>In most test suites the winning move is evaluated as losing by the SEE. So in >>PVS() it gets tried last. In MTD(f) it goes through all the moves every time. >> >>anthony > >Sorry, I still don't understand? I would have thought that move ordering would >be pretty much identical for both methods? Am I missing something? > >My engine is MTD(f) but if I were to convert it to PVS I think it would still >try all the moves in the same order, all things being equal. You should look at >Tord's message as he has some very good advice in there. The convergence >accelerator thing is *very* important. > >Andrew Suppose there are 3 moves, A, B, C. C is a losing capture according to see, so it is tried last. So in PVS(), we get: A B C++ <- c fails high C A B in mtd(F) we get A B C A B C++ C A B C A B C A B C A B in other words, it figures out that the score is higher very rapidly, and plays move C relatively earlier. anthony
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.