Author: Uri Blass
Date: 12:50:41 03/29/04
Go up one level in this thread
On March 29, 2004 at 15:49:40, Uri Blass wrote: >On March 29, 2004 at 15:43:38, Uri Blass wrote: > >>On March 29, 2004 at 15:22:50, martin fierz wrote: >> >>>On March 29, 2004 at 14:30:17, Dieter Buerssner wrote: >>> >>>>On March 29, 2004 at 10:17:18, martin fierz wrote: >>>> >>>>>aloha! >>>>> >>>>>i was discussing this somewhere in a thread, but thought i'd like to make this >>>>>question more visible in the hope of getting a good answer: >>>>> >>>>>everybody knows that with plain alpha-beta, a fixed number of moves N per node, >>>>>and perfect move ordering a search to depth D needs >>>>> >>>>>nodes(depth) = sqrt(N)^(D/2) nodes. >>>>> >>>>>with absolutely imperfect move ordering it needs >>>>> >>>>>nodes(depth) = N^(D) nodes. >>>> >>>>This has not so much to do with your question, but I doubt the last part of your >>>>sentence. I believe, it will be impossible to become as bad as the minimax tree, >>>>even when by purporse ordering the moves "perfectly wrong". You will still have >>>>plenty of situations, where many different moves give a cutoff. In a previous >>>>experiment, I got 50% beta cutoffs for the first move, when randomizing the move >>>>order. Note that this is far away, from a minimax tree (where you would need >>>>100% beta cutoffs in the last tried moves - there are in general many more move, >>>>you try before). >>>> >>>>Regards, >>>>Dieter >>> >>>hi dieter, >>> >>>hmm, everybody writes this that making A/B MO as bad as possible you return to >>>minimax. somewhere below gerd just made the same point as you did here. and if >>>two experienced programmers like you say so, i am of course afraid to contradict >>>you :-) >>>but i have to contradict you all the same. in a perfectly misordered tree you >>>will *never* fail high. which also means that the case that you and gerd were >>>thinking of never happens. >>> >>>cheers >>> martin >> >>I think that it is impossible never to fail high. >>What do you do when all legal moves cause a fail high? >> >>Uri > >Let take for example the following position > >[D]7k/7p/8/8/7q/8/7P/6QK b - - 0 1 > >When you search Qxh2+ what do you search for white in order not to fail high. >The answer is that there is no move for white that does not fail high so your >tree is clearly bigger than the tree when you use minimax. > >Uri I mean clearly smaller.
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