Author: Vasik Rajlich
Date: 15:15:52 03/18/04
Go up one level in this thread
On March 18, 2004 at 17:09:47, Tord Romstad wrote: >On March 18, 2004 at 16:43:02, Mridul Muralidharan wrote: > >>Hi Tord , > >Hi Mridul, > >Are you sure you get enough sleep? :-) > I'm pretty sure he gets enough (sleep+caffeine) :-) >>>If I understand your idea correctly, I do something similar, but less >>>extreme. I extend all checks, but some checks are extended more than >>>others. >> >> >> I did not understand the last part - >>This could mean , you use either : >>1) Allow multiple ply extension per position. >>OR >>2) Use fractional extensions. >> >>Which is the case ? > >Number 2. Checks can be extended anywhere between 1/3 of a ply and >1 ply. I never extend more than 1 ply in a position, except when the >Botvinnik-Markoff extension applies. In this case, I add 1/2 a ply to >the extension. > > >>This was one of the first lessons I learned about how extensions can totally >>screw up your search. > >They can. I still see some rather bad search explotions occasionally, >but not so often that it is a major problem. > >>Ofcourse , by any standards , this was an amazingly crazy position - but still >>it was quiet instructive to study it ! >> >>I do not use fractional extensions - this has the ability of making your search >>path dependent. > >I don't see how fractional extensions by themself can make the search path >dependent. This doesn't necessarily mean that you are wrong; this has been >a long, hard day, and my brain stopped working many hours ago (actually it >never worked very well, but right now it's even worse than usual). > >But my search is already extremely path-dependent anyway. In principle I >don't like this, but the way my search currently works I wouldn't be able >to get rid of the path dependencies without making my search trees many >times bigger. Actually, why couldn't all of your path-dependent extensions be converted to non-path-dependent extensions? Ie. if you are extending something because something happened earlier in the variation, why cannot it be formulated in such a way that you are extending based on something which is currently true about the position. I have had in my mind an idea that I call "committment". In each position reached by the search, both sides have a "committment" to that position. For example, imagine that you start in some position and white plays four consecutive forcing moves. Black is highly committed, if this position is losing, then the root move is winning for white. White, on the other hand, may not be especially committed, since any of his forcing moves had alternatives. My idea for measuring this was by using the results of the null-move searches. (For this you need very good fail-soft.) When a null-move search fails badly, the side playing the null move retains most of his previous committment. When a null-move search barely fails, the committment value goes down. You could do a number of things with this. For example, checks would be extended more when the other side is more committed, etc ... For now the idea is on hold as the failing-soft from null move doesn't appear to be working very well. Anyway, I wonder if path-dependent extensions are somehow related to this. (If the above is a bit confusing, long day here too ...) :-) Cheers, Vas > >>And especially for singular extensions , this can be kill your tree (atleast for >>me). > >I haven't yet tried singular extensions, and I have no ideas what kind of >trouble they would cause in my search. > >Tord
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