Author: Russell Reagan
Date: 14:55:34 04/04/03
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On April 04, 2003 at 15:45:49, Angrim wrote: >The number of entries in the table is the same, but DTC data compresses >better, so after compression the tables are smaller. DTC compresses >better because positions where white can capture usually have a DTC >value of mate in 1, while with DTM the value is much less predictable. > >I seem to recall that for suicide chess, and with my compression method, >the savings from DTC were around 20-30% smaller files. I have often wondered if you could cut the TB's size in half for a little extra computational work when probing. If you stored in your tablebases "codes", you could extract the meaning of a code with a small search. Currently, when you probe you get the actual data. Under the "code" scheme, you get back a code which means something. For instance, let's say that this is our code table: 0: mate in 0 or mate in 1 1: mate in 2 or mate in 3 2: mate in 4 or mate in 5 3: mate in 6 or mate in 7 ... 254: mate in 508 or mate in 509 255: mate in 510 or mate in 511 If you get back a 1, that means the position probed is either a mate in 2 or 3. You would have to do a small search to determine exactly which, but that is trivial, and would only need to be done for outputting purposes. This would lead to a possible non-optimal move being played, but only off by one, and the result should still be the same (so you might play a move leading to mate in 10 instead of mate in 9, no big deal). Maybe things are more complicated in practice than I am aware of. If this does work though, you could get even better space savings than 50%. Your code table could be: 0: mate in 0 through mate in 3 1: mate in 4 through mate in 7 etc... As you searched, you would select moves that made progress from one "mate group" to another, instead of one "mate depth" to another.
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