Computer Chess Club Archives




Subject: Re: Rybka 1.0 Announcement

Author: Gerd Isenberg

Date: 08:31:03 12/05/05

Go up one level in this thread

On December 05, 2005 at 10:49:02, Vasik Rajlich wrote:

>On December 05, 2005 at 10:18:43, Gerd Isenberg wrote:
>>On December 05, 2005 at 04:44:36, Vasik Rajlich wrote:
>>>Well, I am shocked by the speed of the computer chess community. There are now
>>>200 requests for Beta versions of Rybka in my mailbox. Many of you made
>>>interesting comments and asked all sorts of questions, but at the moment I am
>>>really short of time and can't give personal responses to everyone. Some of
>>>these questions are answered here.
>>>The first piece of good news is that Rybka Beta 1.0 will be available for free
>>>download until midnight tonight (Dec 5) on Leo's website. Obviously this targets
>>>the more hardcore members of the computer chess community - there are so many
>>>here who give their time and share their ideas that I would be embarassed to do
>>>anything else.
>>>However, I am now working on this project full time, and much as I would like to
>>>just concentrate on the technical aspect, the truth is that there is now a
>>>business to run. The first commercial release will be as plain as can be - Rybka
>>>1.0 standalone UCI engine, no GUI, no book, no copy protection, no engine
>>>capability not currently specified in the UCI protocol. The price will be 34
>>>Euro. The original target date was Dec 16, but thanks to the incredible speed of
>>>the CEGT team this has been moved up to ASAP :) Additional announcements are
>>>While I hope that there are some sales of Rybka 1.0, the main goal here is to
>>>prepare for a summer 2006 release. If things go as I envision, we'll offer an
>>>engine-GUI combo which brings Rybka's chess knowledge to the user and makes
>>>chess players wonder how they ever survived without it. Of course, some software
>>>developers will tell you that when plans meet reality it is usually reality
>>>which wins .. but in my book reality is a seven point underdog :)
>>>If any of you are interested in helping the Rybka project succeed, the following
>>>are all useful areas of contribution:
>>>1) Comments, feedback, and CPU time for beta versions.
>>>2) Purchase the full version of Rybka 1.0.
>>>3) Get Rybka, and computer chess in general, "out there" into the world of chess
>>>- articles, clubs, into the general chess consciousness.
>>>This last point is for me the biggest. The computer chess community has
>>>tremendous expertise and knowledge, and computer chess is interesting and fun.
>>>As programmers, we struggle with the question of what chess knowledge really is
>>>in a much deeper and more interesting way than chess players do. A chess player
>>>will learn something obvious about positional play, and never really stop to
>>>inspect it - because as a human, he doesn't need to. On the other hand, when
>>>your program is constantly rebeling against everything you taught it, or plays
>>>worse with those last few bits of what you thought were knowledge, you end up
>>>asking much tougher questions. So - for those with the ability and interest,
>>>let's get out there and spread the word.
>>>I am also looking for a few people who will collaborate more closely on the
>>>project. There are the usual computer chess things (opening book, tournament
>>>operation, beta testing). In addition, the main event of the next four to six
>>>weeks will be the addition of I hope two more software developers to the Rybka
>>>team. I have of course a target list from my days as a student and developer,
>>>but if you are talented, and interested in the project, please don't hesitate to
>>>get in touch with me and we can discuss it further.
>>>Happy testing, and best regards,
>>Hi Vas,
>>wow, what great news - seems your bitboard baby has passed some imaginary
>>limits. While Fabien teached us smart search with steady evaluation, your
>>approach implies thinking bitboards in knowledge based implementaion of
>>evaluation as well as quiescence detection.
>>Congratulations and a very big success with Rybka!
>Hi Gerd,
>to tell the truth, I don't think board representation is all that important. I
>flipped a coin my first few weeks of computer chess programming, and it said
>bitboards. :)

hehe - i don't buy that, Vas ;-)

I agree that board representation is not that important ...,
but didn't you agree that "thinking bitboards" - aka using setwise expressions -
isn't more suitable for a lot of pattern ;-)

>BTW: are there any tricks for speeding up bitboards on 32 bit systems. I go from
>166 knps to 104. I was thinking to somehow take advantage of the knowledge that
>sometimes, a bitboard truly is two half boards, but it never gave any speed up.
>I mean, instead of:
>for (bb knights = Board.pieces [WhiteKnight]; knights; knights &= 1)
>  unsigned long knight_sq;
>  _BitScanForward64 (knights, &knight_sq);
>  ...
>something like:
>for (unsigned int i=0; i<2; i ++)
>  for (unsigned int half_knights = (unsigned int *)(Board.pieces [WhiteKnight])
>+ i; half_knights; half_knights &= 1)
>  {
>    unsigned long knight_sq;
>    _BitScanForward (half_knights, &knight_sq);
>    knight_sq += i * 32;
>    ...
>  }
>This was always slower. (I also tried unrolling it, I guess the loop body is too
>If you have any suggestions, I would love to hear them ..

While it might be possible to gain something while processing two half boards
simultaniously, i favour one loop64 approach with some inlined bitscan64
function, which might be conditionally compiled for 64-bit and 32-bit or
"portable"-mode, e.g. with Matt Taylor's folded De Bruijn multiplication:

// some haeder file
// precondition: bb not null
unsigned int bitScan(bb b) {
  unsigned long sq;
  _BitScanForward64 (b, &sq);
  return sq;
extern const unsigned int lsz64_tbl[64];

// precondition: bb not null
// Matt Taylor's folded De Bruijn multiplication
unsigned int  bitScan(bb b) {
  b ^= (b - 1);
  unsigned int fold = ((int) b) ^ ((int)(b>>32));
  return  lsz64_tbl[(fold * 0x78291ACF) >> (32-6)];

for (bb knights = Board.pieces [WhiteKnight]; knights; knights &= knights-1)
  unsigned int knight_sq = bitScan(knights);

// in some c file
const unsigned int CACHE_ALIGN lsz64_tbl[64] = {
 63,30, 3,32,59,14,11,33,
 60,24,50, 9,55,19,21,34,
 61,29, 2,53,51,23,41,18,
 56,28, 1,43,46,27, 0,35,
 62,31,58, 4, 5,49,54, 6,
 15,52,12,40, 7,42,45,16,
 25,57,48,13,10,39, 8,44,



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