Author: Scott Gasch
Date: 11:24:03 06/06/01
Hi, Most of us do not allow two nullmoves in a row in one search line. I know Vincent has some speciual trick for zugzwang detection... but other than him I don't know anyone using this technique. Consider, then, what happens when you make a nullmove in a parent node, recurse into a child node with the reduced depth, and hit a usable lower bound in the hash table. That lower bound you hit could be the result of a previous nullmove indicated by a value with no move attached to it. Right now, in this case, my engine happily fails high in the child and returns a value that causes the nullmove parent in the node above to fail low. My question is this: How is this situation different from allowing two nullmoves in a row? The child node has in essence said "doing nothing is excellent, doing something must be better" just the same as if it had nullmoved. Should hashed nullmove lower bounds be allower in nodes directly under a nullmove? What is the reasoning, if so? Thanks, Scott
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