Author: Robert Hyatt
Date: 07:26:47 10/18/00
Go up one level in this thread
On October 18, 2000 at 09:31:56, Bas Hamstra wrote: >On October 17, 2000 at 10:02:54, Robert Hyatt wrote: > >>On October 17, 2000 at 05:14:14, Bas Hamstra wrote: >> >>>On October 16, 2000 at 10:18:31, Robert Hyatt wrote: >>> >>>>On October 16, 2000 at 06:32:53, Pham Minh Tri wrote: >>>> >>>>>I know that Bitboard makes move generation the fastest, but this structure is >>>>>also one of the most complicated. However, an old post said that the generation >>>>>function is not the key of success to chess program and the author illustrated >>>>>that after his optimality (which made that function work much faster), the speed >>>>>of system increased only 1 percent. >>>>> >>>>>As a result, my question is: is bitboard really worthy for implementation when >>>>>it takes a long time to program and more time to fix all bugs (maybe several >>>>>times bigger than the rest of program)? Or is it better if we use this time to >>>>>concentrate on hash table, null move threshold and so on? I plan that I will >>>>>forget the bitboard (at least in the first period) if it help me only few >>>>>percent. >>>>> >>>>>Pham >>>> >>>> >>>>I see nothing that makes them harder to use than an array. Nor nothing that >>>>makes them particularly easier to use either. >>>> >>>>They have certain advantages on new architectures that move 64 bits of data >>>>around in one cycle, and they have some advantages in evaluation where you can >>>>answer lots of questions in one AND or OR operation. On current machines, I >>>>would say they are no faster nor slower than any other approach. On 64 bit >>>>architectures, they begin to look better. >>> >>>Well if you wanted to build attacked-from tables I would not be so sure. Some >>>programs use that kind of info extensively. If you wanted to make such a >>>program, BB certainly wouldn't be the first option. >>> >>>However I know at least 1 program that builds attacks-to tables with BB and that >>>seems to work fine. >>> >>> >>>Bas Hamstra. >> >> >>Attacks_from works fine in bitboards. Just read the chess 4.x article in >>"Chess Skill in Man and Machine". I did them until I decided I didn't really >>need that often enough to tolerate the overhead. I _still_ get that information >>very quickly if I want it... but I could get it even quicker. Early versions >>of crafty had attacks_from and attacks_to that were incrementally updated as the >>board was modified. I changed to rotated bitmaps to eliminate the overhead of >>the incremental update and turn attacks into a simple table lookup. And I got >>rid of attacks_from almost everywhere except for a couple of places where I >> compute "in check". > >I know you don't use them. So it is logical you leave them out. But not all >program's work like Crafty. There are a couple of programs that use >attacked-from info heavily. They want to know not only that a square is >attacked, but exactly by what. For many squares. > >Now I personally think that if you wanted to do this, you better not use the >rotated BB approach. > > >Regards, >Bas. Why? I used both for a good while. rotated bitmaps help with the attacks_from stuff (move generation/mobility). incremental updates work for the attacks_to stuff (which pieces attack this square). But in any case, I use _both_ in crafty. The attacks_to is required for my Swap() function which is used to order moves and is called a huge number of times.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.