Author: Don Dailey
Date: 13:43:39 01/17/98
In a message from Ed Schroder we run across this statement: > It depends of course how you count NPS. > I remember yours is different then mine. I have long suspected the lack of a "standard" way of doing this. I think most of us use a similar method but it's not so clear. I have always used the method of counting strictly legal moves and requiring that they be fully executed by the program but I can think of good arguments for counting in other ways. For example, most good programs will evaluate a position that hasn't occured yet to save a significant amount of time. An example of this is in quies where you know in advance a capture move will be punished brutally. I do not count count these as nodes but it could be strongly argued that I should. I believe some programs count "moves generated." This is not an issue if you are using a purely incremental move generation but would inflate (or deflate depending on your point of view) the node counts since most of these moves get cut off before they are even considered. Another method is to count end nodes only, which will deflate your node counts over my method but probably not by large amounts (depending on a lot of factors like the shape of the tree.) Some programs generate and "make" illegal moves as part of the testing for legality. I view this as inefficient but leads to the question of whether these should be counted as nodes. When I do check testing to determine if a move is legal should I count this as a node since in some sense I'm definitely evaluating it? I don't, but maybe I should? This adds a significant number of nodes to the nodes/second count. I am always reluctant to attach any significance to big (or small) node count claims. Until you can actually compare apples to apples it can be quite misleading. Also this is certainly not the true measure of a chess program but nevertheless it's an interesting topic. Certain programs claim such high node counts that it's hard for me to believe they are counting nodes the same way that some others might be. What is known about the various programs and how they count nodes? I am quite interested in this since it can give some insights into how each program works. P.S. Please forgive me if this discussion has already made the rounds but I've never heard any of it myself. - Don
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