Author: J. Wesley Cleveland
Date: 10:32:54 08/30/05
Go up one level in this thread
On August 29, 2005 at 16:28:39, Eugene Nalimov wrote: >On August 29, 2005 at 15:57:51, Joshua Shriver wrote: > >>Good Afternoon, >> >> What is the WDL format? I've unsuccessfully been able to find information >>on it. Is it a chess specific compression of general data? >> >>-Josh > >Store only Win/Draw/Lost value for every position, not the full value (Win in >N/Draw/Lost in N). > >The simplest way to encode them would be to fit 5 values in a byte. 3**5 == 243, >that is less than 256 different values, so you can store them into a byte. When >probing you can easily get a value by using 243-element decode table (much >faster than divisions). > >Other possibility would be to store 4 values into a byte -- 2 bits per position. >Such table would be larger by itself, but it may compresses better -- when I >experimented resulting compressed tables were smaller. > >Or you can store 2 tables -- one with Win/No Win, and other with Lost/No Lost. >Presumable they will compress even better, and in lot of cases during the search >you will probe only one of them, because that is all you need to know. > >Of course all those tables have drawback: you should assume that chess program >that uses only them will be able to win a won position. E.g. it knows that OTB >position is won. It know that out of all moves 3 moves also lead to won >positions. Unfortunately it may not be able to figure out that current position >is (say) mate in 30, move A leads to mate in 29, while moves B and C -- to mate >in 35, and it may decide to make the wrong move. Hopefully such situation is >rare enough, but I suspect it is more often when position is complex enough -- >i.e. exactly when you need TBs. > >Thanks, >Eugene Ideally, you would have both. Use WLD in the search and the full table at the root. If disk space is a problem, just have the full tables for the difficult cases. >>> >>>It's just computational problem, all you need is 1 array of 2 TB to >>>generate it, and after that supercompress it to WDL format. DTZ is >>>perhaps interesting to generate if your goal is to publish near to >>>maximin positions, but from computerchess viewpoint what matters is the >>>result in the game. That can be either one of the next 3: win, draw or loss. >>> >>>Supercompressed this EGTB in wdl is like 3GB. >>> >>>Additional i'm interested in knowing what from their database what the longest >>>win is for the KRB side in the KRBNKRB egtb. >>> >>>Vincent
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