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evaluate loose pieces
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Eelco de Groot



Joined: 12 Mar 2006
Posts: 2591
Location: Groningen
PostPost subject: Re: evaluate loose pieces    Posted: Sun Feb 26, 2012 5:57 pm Reply to topic Reply with quote
lucasart wrote:
lkaufman wrote:
A bonus for attacks on loose pieces (or up-attacks) is quite standard. I introduced it in Rybka, it was duplicated in Ippolit, and of course is in Komodo. Since the Ippolit code is open-source, there is nothing secret about how this was done.

Yes, of course I can have a look at IvanHoe's source code, and many other source codes. But I want to build my own stuff from my own understanding rather than copy... Anyway, I'll have a look at how IvanHoe does it and Stockfish too, just to see if there are some ideas (not code) I can use there.


The surprising thing about Stockfish way of implementing is that at least I could not find code that takes into account undefended ("loose") pieces in general for evaluating attacks from the opponent, only a defence by one's own pawns. I think I introduced including defences by other pieces (which is all already existing bitboardcode in Stockfish, but it just was not used for evaluating attacks) to Rainbow Serpent and other clones of Stockfish then, just like Larry did in Rybka Smile but it is not much tested. Maybe it is only not in Stockfish because it did not bring much elo, I don't know.

Evaluating attacked pieces in general was not in Fruit or Toga, which being non bitboard programs is not such a surprise. But also not in Glaurung after that moved to bitboards and I also can't remember hearing Bob Hyatt talk about this so it probably is not yet in Crafty? So from that point of view it is also maybe not such a surprise Vas had not heard of it yet, and the introduction in Stockfish by the Stockfish team came indeed after the code from Ippolit went public. That is the other side of the medal, if I just want to talk about Stockfish attack code.

I have experimented also, in one Ancalagon I think it was, with increased bonuses if the attacked piece does not have the move (sente/gote code) but I was not enthusiastic in the end about what probably amounts to search instabilities caused by this. Also have experimented with more than just additive bonuses in Stockfish if more than just one piece is attacked, like you are suggesting in your other post Lucas, but the way it is implemented in Stockfish makes it a bit hard (or more expensive) to count attacks for instance, it does not count separate attacks from a type of piece on another type of piece, just registers if the second type is attacked, not how many times it is attacked. This code I also abandoned, it was also too messy I think. Also experiments with X-Ray attacks are possible, to include pins but in a 32 bit environment the needed popcounts are a bit expensive. The X-ray/pin detection code is still lying around somewhere in old archived code but not in use in Rainbow Serpent now.

Regards, Eelco
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Subject Author Date/Time
evaluate loose pieces Lucas Braesch Sun Feb 26, 2012 5:20 am
      Re: evaluate loose pieces Larry Kaufman Sun Feb 26, 2012 3:57 pm
            Re: evaluate loose pieces Lucas Braesch Sun Feb 26, 2012 4:11 pm
                  Re: evaluate loose pieces Eelco de Groot Sun Feb 26, 2012 5:57 pm
                        Re: evaluate loose pieces Michael Hoffmann Sun Feb 26, 2012 6:53 pm
                        Re: evaluate loose pieces Marco Costalba Sun Feb 26, 2012 7:04 pm
                              Re: evaluate loose pieces Eelco de Groot Mon Feb 27, 2012 12:46 am
                                    Re: evaluate loose pieces Marco Costalba Mon Feb 27, 2012 7:17 am
                                          Re: evaluate loose pieces Lucas Braesch Mon Feb 27, 2012 10:20 am
                                                Re: evaluate loose pieces Sam Hamilton Mon Feb 27, 2012 10:23 am
                                          Re: evaluate loose pieces Lucas Braesch Mon Feb 27, 2012 1:40 pm
                                                Re: evaluate loose pieces Evert Glebbeek Mon Feb 27, 2012 2:34 pm
                                          Re: evaluate loose pieces Marek Kwiatkowski Mon Feb 27, 2012 2:58 pm
                                          Re: evaluate loose pieces Eelco de Groot Mon Feb 27, 2012 9:45 pm
                                          Re: evaluate loose pieces Gary Tue Feb 28, 2012 1:35 pm
                                                Re: evaluate loose pieces Marek Kwiatkowski Tue Feb 28, 2012 2:35 pm
                                                      Re: evaluate loose pieces Joona Kiiski Tue Feb 28, 2012 4:04 pm
                                                            Re: evaluate loose pieces Marek Kwiatkowski Tue Feb 28, 2012 5:57 pm
                                                            Re: evaluate loose pieces Eelco de Groot Fri May 25, 2012 11:36 pm
                                                      Re: evaluate loose pieces Gary Tue Feb 28, 2012 4:04 pm
                              Re: evaluate loose pieces Lucas Braesch Mon Feb 27, 2012 3:57 am
                        Re: evaluate loose pieces Sam Hamilton Sun Feb 26, 2012 7:12 pm
            Re: evaluate loose pieces Miguel A. Ballicora Sun Feb 26, 2012 5:11 pm
                  Re: evaluate loose pieces Larry Kaufman Sun Feb 26, 2012 5:20 pm
                        Re: evaluate loose pieces Sam Hamilton Sun Feb 26, 2012 6:50 pm
                              Re: evaluate loose pieces Lucas Braesch Mon Feb 27, 2012 3:59 am
                                    Re: evaluate loose pieces Sam Hamilton Mon Feb 27, 2012 4:28 am
                  Re: evaluate loose pieces Ed Schroder Mon Feb 27, 2012 11:42 am
            Re: evaluate loose pieces Gerd Isenberg Sun Feb 26, 2012 7:56 pm
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