Author: Inmann Werner
Date: 00:30:13 08/26/99
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On August 25, 1999 at 10:59:45, Robert Hyatt wrote: >On August 25, 1999 at 08:21:32, Bas Hamstra wrote: > >>My program returns sometimes values outside (a,b), for example MATE. I believe >>generally when you allow this, it is called "fail-soft". What is the advantage >>of it? >> >>I vaguely have read somewhere that the advantage lies in better bounds >>information. In interprete that as: you put better bound info in your hashtable. >>Is that correct? If so, is it a factor? >> >>Secondly: I use simple alpha beta (not even pvs) with an aspiration window. Now >>at some testposition it fails high at the root and score turns out to be 250. >>New aspiration window is set (200, 300). >> >>Now it fails low. However: full (-inf,inf) gives 243!! >> >>I use no pruning at all. Could the cause be the returning of values outside >>(a,b)? I think my basic routines are correct, including hashtable. Only thing I >>do is strip losing captures from the qsearch. >> >>Last: *if* fail soft has advantages, what are the disadvantages? >> >>Regards, >>Bas Hamstra. > > >The advantages are minimal but do exist. > >1. when you fail high or low, you have some 'estimate' of how far outside >the window the true score will end up, so that you might choose to avoid >setting beta to +inf or alpha to -inf, for example.. > >2. you get slightly better bound information stored in the hash table, so >that there is a better chance that these bounds will be used later. > But isn't that risky. I thought, each score outside alpha-beta can be incorrect, and then store it in Hashtables for bounds? Can't that give irregular things? Werner >3. if you try mtd(f) it is critical to get the better 'estimate'...
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