Author: leonid
Date: 18:27:15 03/02/02
Go up one level in this thread
On March 02, 2002 at 20:14:33, Heiner Marxen wrote: >On March 02, 2002 at 19:43:41, leonid wrote: > >[snip] > >>Just tried this position with new selective version and, bingo! Mate in 10 moves >>in zero seconds. >> >>Actually, before my selective version had three "mixed" searches and now I have >>5 of them. Mixed search - search start with brute force and later goes by >>selective. Selective - attacking side look only promissing moves and also number >>of responses is limited. In my version last Summer my three version of "mixed" >>search had 1, 2 and 3 moves deep brute force before selective. Now this brute >>force search goes as far as 5 moves. When I asked to search in 5, "mixed" search >>response was instant. I not even tried to search for 4 moves brute force search >>in mixed. >> >>It could be that in your future selective search (if you will be interested one >>day to install it) you can try something like I did. > >Well, sure I am interested! Unfortunately, this is more complicated as it >sounds when the hash table gets involved (you do not yet have it :-), >since interior nodes (positions) can be solved/asked with different kinds >of jobs, which are not always clearly sorted. I'll explain... > >With normal brute force (or also purely selective) any position's job/result >is characterized just by the depth. If a hash table entry stores "no solution >in depth=5", we immediately know the answer for all smaller depths. >And if a larger depth is asked for, we have to compute it, but later also >will store the new result, since the old result will be implied by the new >one and will not be lost. > >If now the job for a position is characterized by two numbers, namely the >depth like before, and an additional value, how many of the moves may be >unrestricted, the new job and the old job may be uncomparable. >Consider, the hash entry says "no solution in 4 moves with 2 full width", >and now I ask for a solution "in 5 moves with 1 move full width", then >neither the old implies the new, nor the new implies the old. Which one >will I store? If search is done by selective it signify that way of search is indicated explicitly by user. If no mate was found, user have its chance to indicate its new selective search, or stop search completely. With this kind of mate solver, brute force search is only next version of search that user can chose when he like it. Selective search with in advance indicated number of responses to see (special variable accessible to user) could go, probably, before every of your brute search. It could be useful, sometime, since selective search time could be rediculously small. But each time when program have as its goal to see all possible solutions, selective have no reason to be included. If hash is somehow problem, you can try (just for you and for fun) to write some selective search. I am sure that with your actual moves order, your selective will fly more quickly that in Chess Master at first try. Chess Master time is excellent! Cheers, Leonid. >And if I try to store more than one result, how many of them? If I have >room for all of them, this costs considerable amounts of memory, which I >rather would like to use for more hash entries. > >I have not yet found a convincing solution for this mixed results problem. >Of course, there also should be some special handling in the last plies, >which is doable, but a bit complicated with my current heuristics. > >Still, selective search is a very attractive thing, and I will do something >about it, sometime. > >Cheers, >Heiner
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