Author: Marc Bourzutschky
Date: 11:41:00 08/29/05
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On August 29, 2005 at 13:46:48, Vincent Diepeveen wrote: >On August 29, 2005 at 13:13:33, Marc Bourzutschky wrote: > >>On August 29, 2005 at 10:27:17, Vincent Diepeveen wrote: >> >>>On August 29, 2005 at 03:15:54, Marc Bourzutschky wrote: >>> >>>Hi Marc, >>> >>>I just don't understand how you manage to generate a mate in 250 with >>>just 500GB i/o size for krbn krb. >>> >>>I need like 2 TB raid5 array or something for my generator for 7 men >>>I'm using bitmaps which are similar to mate in n, though not entirely, >>>as i just care for WDL. >>> >>>that means you basically need from -mate256 to +mate255 = 9 bits per >>>entry. >>> >>>Diep's entry size is probably bigger with 358G entries than what is possible >>>if you use nalimov's scheme, i'm using my own one which simply avoids more than >>>1 piece at the same square, no illegal reductions are getting done. >>> >>>Anyway. 2 files of 358G * 9 bits per entry is more like 800GB than it is >>>close to 500GB. >>> >>>How do you fit this EGTB onto just 500GB disk? >>> >> >>As described in the post, we split krbnkrb into two components, depending on the >>relative color of the bishops. This reduces the problem to two independent >>generations with each half the size. In addition, we use on-the-fly >>compression. We used less than 250 GB during generation. > >Hello Marc, > >Thanks for your answer! > >So you didn't split the bishops in 4 components: > white bishop for KRBN side and white bishop for KRB > white bishop for KRBN side and black bishop for KRB > black bishop for KRBN side and white bishop for KRB > black bishop for KRBN side and black bishop for KRB > >of course assuming you rotate 8 fold over the king positions and >not the bishop (as there is less bishops in that case). > No, since we restrict ourselves to the usual 462 symmetry equivalent king positions for pawnless endings. The color of any individual bishop cannot be fixed, because some of the symmetry operations to get the kings into one of those 462 positions would change the color of the bishop. Only the relative color of two bishops can be fixed, since that is invariant to all the symmetry operations. >how many entries does your indexing scheme use for one of those >files KRBNKRB? 462*(64^5)/2 >how many bytes (or bits) per entry did you use at generation time? Only a few bitmaps for a subset of the 462 king-king positions are in memory during generation. 1 bitmap for 19 different king-king positions, plus two additional bitmaps for a given king position. A general 7-man endgame thus requires 21 * 64^5 / 8 = 2.8 GB of RAM. With permutation symmetries or bishop parity tricks this can be reduced accordingly. We'll give more details in a technical paper we are working on. -Marc
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