Author: Tony Werten
Date: 05:21:47 07/07/04
Go up one level in this thread
On July 07, 2004 at 07:51:09, Tord Romstad wrote: >On July 07, 2004 at 07:35:01, Tony Werten wrote: > >>On July 07, 2004 at 05:49:44, Tord Romstad wrote: >> >>>On July 07, 2004 at 05:43:49, Tony Werten wrote: >>> >>>>On July 07, 2004 at 05:22:22, Tord Romstad wrote: >>>> >>>>>On July 07, 2004 at 02:26:30, Tony Werten wrote: >>>>> >>>>>>>5 3 .6 mate-at-a-glance >>>>>> >>>>>>From my experience, the effort is higher, since it's a very dangerous piece of >>>>>>code. Specially since other wrong scoring seems to get damped by alpha beta, but >>>>>>a wrong score by a maag is deadly. >>>>> >>>>>This depends on how you use it. When I used static mate detection, I didn't >>>>>return a mate score, but just used the information for move ordering. The >>>>>mating >>>>>move was searched first. This works very well, even if the mate detection is >>>>>correct only 99% of the time. >>>> >>>>Yes, but that's not a mate at a glance but a move ordering trick. >>> >>>Technically speaking you are right, but the effect is exactly the same >>>as a "mate at a glance". >>> >>>>Less effort but also less result. >>> >>>I agree about less effort, but less result? The only disadvantage of >>>using the static mate threat detection only for move ordering is that >>>you have to do an extra makemove/unmakemove before returning a mate >>>score. Not an expense worth mentioning ... >> >>I understand the difference. A mate at a glance should go further than a mate in >>1. > >Yes, if you want to detect mate in several moves, the difference in efficiency >increases a bit. > >>Mate in 1 is easy, specially if you have attacktables. > >Attack tables make it easier, but it is still by no means trivial. One >problem is "X-ray defences" through the attacking pieces. My attack >tables don't contain this kind of information. > >>eg you give a check at the back rank, your opponent can put various pieces >>between your checking piece and his king, but they are all undefended and can be >>captured, so the maag returns checkmate in 3. > >No, it is much more complicated than that. I know :) It has cost me a few points. An undefended piece that can become defended is only 1 of the problems. A very nasty one was a knight on h7 and a king on h8 (pawns on g7 and f7) where the undefended knightmove to f8, opens an escape on h7. IF of coarse the knight wasn't pinned by another piece than the one giving the check. etc etc Quite powerfull if it works correct. Very deadly if it doesn't. All in all, a nice programming excercise. >Consider the following position: > >[D]7k/R4rpp/4r3/8/8/1b6/8/7K w - - > >Unless you have some very sophisticated attack tables, you cannot easily >see that white has no forced mate. It does depend on how precise you want to be and how much time you have to spend. The easy way out is not to reward the checkmate if the defending piece is defended by a slider and the opened up square is closer (measured in ranks if you give a rank check else in files ) to the checking piece square than the slider from-square. Even easier is to jump out if a defender is defended by any slider at all. That also solves the problem of revealed checks :) Tony > >>If this happens in quiescence, >>it's not sure your normal search would find it as well, even if you do some >>plies of checking moves in qsearch. > >One of the criterions for when to search checks in the qsearch should of >course be the presence of a likely mate threat. > >Tord
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.