Author: Pham Minh Tri
Date: 15:28:59 11/01/00
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On November 01, 2000 at 13:25:23, Ernst A. Heinz wrote: Hi Dr. Ernst, >Hi Pham, > >>In the book "Scalable Search in Computer Chess", Dr. Ernst A. Heinz >>said, "The best chess programs generate search trees with only 20%-30% more >>nodes on average than the critical alpha-beta trees" (pp 22). > >I am always amazed how much people like to quote statements >out of context, thus making them look weird and fishy. Sorry, I am new to computer chess and still learning and looking for documents. I have only few materials and your book is one of the best so I read it most. Therefore, when I ask for checking my understanding, I always try to quote from what I have without experience. Your answer is good and enough for me. And I will try to find the original materials as your suggestion. Thanks. Pham > >If you had cared to mention that the quote originates from >a subsection of the book called "Move Ordering", the 20% to >30% overhead should have been easy to understand. It simply >quantifies the effectiveness of move-ordering schemes used >by state-of-the-art chess programs in their PVS searches in >comparison with the best-first move ordering of critical >trees. Of course, you must do fixed-depth searches with >uniform path lengths (i.e., without any forward pruning or >extensions) in order to measure this overhead. > >Now, if you add forward pruning and large transposition >tables leading to frequent cutoffs, the effective trees >searched by modern chess programs actually shrink to less >than half the corresponding critical trees of a standard >alpha-beta search. > >>- I guess that Dr. Ernst A. Heinz does not concern some techniques like >>hash table, null move, rasoring and so on, which make the real trees could be >>much smaller than critical trees. > >Yes, see above -- the 20% to 30% overhead solely relate to >move-ordering issues. They are meant to show how well good >schemes for move ordering (such as the one given in my book) >work with PVS searches in computer-chess practice. > >=Ernst=
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