Author: Christophe Theron
Date: 10:56:02 06/21/00
Go up one level in this thread
On June 21, 2000 at 13:30:25, Tom Kerrigan wrote:
>On June 20, 2000 at 21:02:15, Christophe Theron wrote:
>
>>On June 20, 2000 at 14:51:25, Tom Kerrigan wrote:
>>
>>>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...
>>>
>>>But with bitboards, there is more memory overhead. Sometimes you have to take
>>>that into consideration. With modern desktop PC processors, it's probably not a
>>>big deal. But I'd like my program to run on smaller computers (specifically
>>>palmtops) so I'm going with 0x88.
>>>
>>>-Tom
>>
>>
>>That's a good reason indeed, and could even be the ultimate argument to say that
>>bitboards are not the best way to go.
>>
>>Some people are not afraid to allocate a bunch of 64 bits (=8 bytes) integers. I
>>am. I don't want to blow out the cache of my processor.
>>
>>Some will say that in a few years from now L1 caches will be much bigger.
>
>I doubt it. Big L1 caches can only slow a chip down.
>
>-Tom
I did not expect that. Can you explain why? I know you have more knowledge about
hardware than I have.
Christophe
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.