Author: Robert Hyatt
Date: 18:25:44 03/11/98
Go up one level in this thread
On March 11, 1998 at 19:00:13, Will Singleton wrote: >Progress on tt table implementation - > >Following advice, I wrote a validate routine to test whether the >incremental hashkey matched a value calculated from scratch. Sure >enough, errors popped up, which were related to ep, promotion and >castling. Those are fixed. > >I've done some early data-gathering, resulting in the following >observations: > >The percentage of true transpositions appearing in the table, for which >a value can be returned immediately as the true score of the position, >is small. That is, using iterative deepening, a ply 6 search can only >find transpositions within its current search, and none from the >previous ply 5 search. That would hold true for scores which narrow the >window. actually you can get a transposition in a 5 ply search... from the starting position for example: Nf3 Nf6 Ng1 Ng8 and there's a position you should have kept from the 1 ply search you did first... > >The main value of tt tables is to order the search by using moves that >have caused cutoffs in stored positions, and may do so again. > >As for specific observations, my node count is down to about 60% of what >it was without tt-tables. The number of tt hits from ply 6 to 7 (in the >table below) increase by a factor of 3, while the overall nodes from ply >6 to 7 increase 20 fold. Doesn't seem right. Amateur's node count is >excessive, but I'm only using killers and transpositions (and some >extensions). Move-ordering is tt-move, killers, good captures, rest of >moves. But even so, compared to Hiarcs especially, the node count seems >pretty high. the above seems wrong. good captures should come before the killers, always... > > >Test position results -- 7 plies > >r2n1rk1/p4ppp/1qb1p3/4P1B1/1p1Pp1NP/1Pp1Q1P1/P1P2P2/3RR1K1 w - - >--------------------------------------- >Amateur -- with tt tables -- >thru ply 6 - move=Nh6 score=162 nodes=118302 > tt hits=13204 tt cutoffs=11337 >thru ply 7 - move=Bf6 score=521 nodes=2068354 > tt hits=32687 tt cutoffs=13807 > >Amateur -- without tt tables -- >thru ply 6 - move=Nh6 score=162 nodes=199272 >thru ply 7 - move=Bf6 score=553 nodes=3514276 >--------------------------------------- > >Hiarcs -- >pv Bf6 h6 Bxg7 f5 Qxh6 fxg4 Qh8+ Kf7 Qxf8+ Kg6 Qf6+ Kh7; >score 631; nodes 120121 >--------------------------------------- > >MacChess -- >07/33|00:00:11| Nh6+ Kh8 Be7 Re8 Bxd8 Qb7 Nxf7+ Qxf7 Bg5; >328862 (nodes) tt-hits:11095 tt-cutoffs:7605
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.