Author: Robert Hyatt
Date: 17:26:12 04/10/00
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On April 10, 2000 at 18:45:23, Eelco de Groot wrote: >On April 10, 2000 at 14:45:13, John Coffey wrote: > >>Let me get this sraight.... >> >>1. hash is the transposition table. >>2. hashp is pawn structure caching? >>3. cache is used for tablebase caching? >> >>How does one cache tablebase stuff? It is all endgames so I am not sure I see >>the benefit. I guess that the exact same endgame could arrise in multiple >>continuations. >> >>John Coffey > >I don't know much about how these hash tables are built up, -I do think you are >right about hash, hashp and cache-, but if the number of pieces on the board >goes down the number of transpositions that you will see in a typical position >and chess-tree goes up by a lot. That's why hashtables (transposition tables) >are especially effective in endgames. So that would also be true with only 3 to >5 pieces on the board then. If you can search the transposition tables faster >than the endgame tables on CD or on harddisk, compressed or not, such tablebase >caching would pay off. I don't know if for Robert Hyatt's Crafty on the Quad the >tablebases are also accessed while they are still compressed? In that case >transposition tables would I think be faster still. But once a program is >actually in a 3 to 5 piece sitation, would it then not be possible to use all >room in the normal hash for just the endgame tablebase caching? And, if in >Shredder's case the endgame tables are still on (Turbo-)CD I don't understand >why Shredder wouldn't profit from more than 4 Mb? As I said I don't know that >much about the subject. If maybe somebody could edify a little? (Like Dan's >Encyclopedia Brittannica I mean?) > >Thanks >Eelco As counter-intuitive as it sounds, compressed on-the-fly accesses are faster for almost all machines. A compressed block has to be decompressed, for certain. But you read in more useful data in a compressed block than in an uncompressed one (several times as much data). Which means that when using compressed data, the effective I/O thruput goes up by a factor of 5 or more, which more than offsets the time to decompress... I am using compressed databases (with raid0 in linux) to _really_ make I/O fly...
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