Author: Tord Romstad
Date: 04:51:09 07/07/04
Go up one level in this thread
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. 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. >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
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