Author: Roberto Waldteufel
Date: 22:28:56 10/04/98
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On October 04, 1998 at 10:18:31, Ernst A. Heinz wrote: >On October 03, 1998 at 19:09:59, Roberto Waldteufel wrote: >> >>Here's another trick. I don't know if anybody else has tried this, but it might >>help improve efficiency when there are large numbers of tablebase hits in the >>search. Normally the tablebase would store an evaluation like draw or +mate in N >>or -mate in N. Now the search only needs to know win/draw/loss except at the >>root, where the best move is also needed. We can store win/draw/loss in 2 bits >>per position, which is less than the space to store mate in n type scores. By >>making the tablebase very compact, we may be able to store it in RAM, increasing >>speed by avoiding many disk accesses. When we actually reach a tablebase >>position at the root, the 2 bits of information are insufficient, so we store a >>second, larger tablebase on disk with a move for each position, and just look up >>the move at the root (we could also store number of moves to mate, but that is >>not necessary). Does this make sense? > >Roberto, > >You are absolutely right here -- with some improved indexing schemes (article >already submitted to the ICCA Journal :-) you can compress *all* 3-piece and >4-piece tablebases to less than 16MB of RAM. I have done it in "DarkThought" >since summer 1997 together with my efficient interior-node recognizers and it >works great. "DarkThought" probes the databases at speeds of at least 500K nps >and peaked at over 1M nps during the last WMCC in Paris on the 767MHz >DEC/Kryotech Alpha-21164a. The tricky part is to write sound evaluation >functions that fit together with your static evaluation. > >I am currently writing another article for the ICCA Journal which details >exactly how I do it. Please stay tuned ... :-) > >=Ernst= This sounds great! I look forward to seeing your article soon...:-) Best wishes, Roberto
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