Author: Robert Hyatt
Date: 17:08:09 08/27/02
Go up one level in this thread
On August 27, 2002 at 19:03:52, Uri Blass wrote: >On August 27, 2002 at 18:18:03, Robert Hyatt wrote: > >>On August 27, 2002 at 16:09:35, Uri Blass wrote: >> >>>On August 27, 2002 at 15:51:38, Robert Hyatt wrote: >>> >>><snipped> >>>>>The question is if they mean to the plies that they sacrificed for the singular >>>>>extensions. >>>> >>>>I believe so. the only comment to any sort of selective forward pruning that >>>>I have ever heard from then was the futility pruning comment regarding the >>>>chess processor. In the games vs the micros, they said that they turned this >>>>off which slowed them by a factor of 10 or so, somehow... >>> >>>The point is that they did not say in the paper that they sacrificed 2 plies for >>>singular extensions but that they sacrificed 2 plies for selective search >>>algorithms. >>> >>>singular extensions are not selective search. >> >>yes they are, as I have explained before. "selective" means "to choose >>between". You can choose to forward prune, or you can choose to selectively >>extend certain lines. Either can be used to produce the same search tree/ >>result... > >By this definition all the programs do selective search because >check extensions are also selective search. Aha. That is _the_ point. :) And, of course, some programs are more selective than others. Either by doing _more_ extensions or _more_ forward pruning or _both_... > >If they mean only to extensions they could say directly that >they sacrificed 2 plies for extensions. As I said, most AI papers consider extensions applied to certain parts of the tree to be "selective" since you select where to apply an extension or where to not apply the extension... I won't argue that even though the two produce identical results, they are done in quite different ways and should be identified with different names. But, alas, that isn't the way things have been done in the past, which means it will continue into the future. > >I understood selective search as selecting part of >the moves and not anlayzing the other moves. It could be selecting a sub-set of moves to search farther, or selecting a subset of moves to extend farther, or selecting a subset of moves to search less deeply, some of the above, or all of the above... Note the word "select" used over and over... > >This is different than singular extensions because the other moves >are also analyzed to reduced depth. Different in implementation. Not necessarily different in result. IE you extend every check by one ply. I reduce the depth of every move that is not a check by one ply. I will search one "ply" deeper. yet our trees will include _exactly_ the same number of nodes and the same tactical acuity... > >> >>Their idea of selective search was _always_ to extend interesting lines, while >>the forward pruner's idea is to discard uninteresting lines early. >> >>>selective search is what computer did in the past when they were not fast >>>enough. >> >>Not necessarily. Forward pruning _is_ one definition of selective search. >>But it isn't the _only_ definition. See above. All that "selective search" >>requires is that some lines be searched more deeply than others. Forward >>pruning or selective extensions both do this... >> >> >> >>> >>>No doubt that it does not make sense to do selective search close to the root >>>but doing selective search in the last 6 plies is a possible idea to consider. >>> >> >>Yes... IFF you mean "forward pruning" when you say "selective search". > >Yes this is exactly what I mean. > >Uri Then you should say "forward pruning" all the time. But just because you say that doesn't mean everybody will follow suit. And that is the problem that is hard to solve... Probably "selective search" is going to always be a fuzzy description that applies to a broad set of algorithms...
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