Author: martin fierz
Date: 19:14:57 09/11/02
prompted by the discussion on MTD before, i decided to look once again what my program does. 1. observation dann corbit suggested that MTD works "binary-search-like" in zooming in on the true value, in the sense that it converges rapidly. assuming the grain size of my eval to be 1, i have seen ONLY search window changes of 1. like when my eval jumps from 0 to 10 (0,1) returns value 1 (1,2) returns value 2 ... (9,10) returns 10 (10,11) returns 10. not once did i see it do something like (0,1) returns value 9 i forget which is which, fail-soft/fail-hard, but i'm using the one which returns the maximum of the successors, not the one which returns beta. so in theory (0,1) could return 9, but it never does. i guess that's not really surprising, since alpha-beta just tries to do as little work as possible :-) 2. question my question is related to bob's "bouncing over". MTD necessarily has to bounce over once, as in the example above, it has to search both (9,10) and (10,11), and fail high on the first search, and fail low on the second. so the question is: isn't this bouncing over too? and if this is really bad, then: has anybody ever measured the difference between MTD storing just one bound in the hashtable with storing both bounds? cheers martin
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