Author: James Robertson
Date: 11:34:37 06/20/00
Go up one level in this thread
On June 20, 2000 at 14:21:23, Christophe Theron wrote: >On June 20, 2000 at 11:17:48, Andrew Williams wrote: > >>On June 20, 2000 at 09:02:26, Robert Hyatt wrote: >> >>>On June 20, 2000 at 04:55:22, Dann Corbit wrote: >>> >>>>On June 20, 2000 at 04:41:47, James Robertson wrote: >>>> >>>>>Ignore all results from my previous post "Rough comparison between ro....". I >>>>>made some stupid coding errors in my test rotated bitboard code. Once fixed the >>>>>rotated bitboards look very competitive against 0x88. :) I also found flaws in >>>>>my 0x88 code, but they were very minor and I think I caught all of them (correct >>>>>move lists are generated in all my test positions). >>>>> >>>>>I am very happy to continue to use rotated bitboards. Thanks Robert for >>>>>inventing them, and thanks Tim for showing me how to use them! >>>> >>>>What was the timing ratio for various operations between the two methods? >>>> >>>>For the 0x88, what board size did you use? >>> >>> >>>For 0x88 you don't have much choice... it has to be 128, where you use the left >>>half for the board, the right half (64 squares) are off the board. There is >>>really a top half of 128 words also, but 0x88 eliminates references to them >>>due to the 0x80 bit not being allowed. >> >>Christophe Theron posted a few interesting pointers to using 16x16 instead of >>16x8 last week (I think). >> >>Andrew > > >Yes. I think that comparing 0x88 and bitboards is not totally relevant, as 0x88 >is in my opinion suboptimal. I explained why in last week's posts. > >There are also many smart tricks you can use that are derived from the >properties of a 16x16 (or 16x12) board, and they have never been published. > >I don't believe it is possible to compare 0x88, 16x and bitboards in one day or >two. Once you start to use one system, you discover smart ways to optimize it >even months after you start using it. > >I think that 16x and bitboards just break even, even on 64 processors, but it >would probably be very difficult to demonstrate this... > > > Christophe I don't think we will ever know which is better, as there will probably never be someone who spends enough time at both to find every clever trick a system provides. I think I would stick with bitboards even if I knew their absolute max move generation speed to be 1/2 the 16x absolute max. First, 1/2 the speed in move generation is not that much when translated into a complete chess program, and second, I have so much more experience with bitboards that I would be able to bring them closer to some "absolute" potential than any other representation to its "absolute" potential. James
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