Author: Andrew Williams
Date: 13:06:19 06/04/01
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On June 04, 2001 at 14:58:18, Uri Blass wrote: >On June 04, 2001 at 14:52:13, Andrew Williams wrote: ><snipped> >> 1= 0 0 23 1. a3 > >Can you explain how did you get 23 nodes for depth 1. > >even if I use minimax I can think of only 21 nodes with no extensions(the root >position and 20 positions that are 1 ply after it). > >Uri Before doing any work, my Memory Test Driver function (called mtdf()) knows that the score will fall between -100000 and +100000. Its first guess is that the score will be 0: It calls root_AB(), which is the function which handles searches from the root node in PostModernist. It wants to know if the score for the root position is greater than or less than 0. This call generates node number 1. root_AB() generates the move 1.a3 and calls alphabeta(), which drops straight into quiesce(), which finds no captures. This qNode is node number 2. This returns a score of 0, which goes back to the root and then back to mtdf(), which now knows that the score is >= 0 (and <= +100000). Now mtdf() tries a new guess, which will be 1. Now it wants to know if the score is greater than or less than 1. It calls root_AB() again, this time generating node number 3. root_AB() generates 1.a3 and calls alphabeta(), which drops straight through to quiesce(). This is node number 4. There are no captures, so quiesce() simply returns the evaluation score, which is zero. This is less than the guess, so root_AB() makes the move 1.a4 and calls alphabeta(), which calls quiesce immediately for node number 5. etc We've traced the first five nodes and we still have eighteen moves from the root position which we need to prove don't lead to a score which is greater than or equal to the guess which is 1. 5 nodes so far, plus eighteen more processed in the same way = 23 nodes for the first ply. Andrew
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