Author: Fabien Letouzey
Date: 03:39:25 07/27/04
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On July 26, 2004 at 23:48:46, Pham Hong Nguyen wrote: >On July 26, 2004 at 19:47:21, Peter Alloysius wrote: >>What's the different between negascout and PVS ? They look like the same >>algorithm to me. >Yes, they are the same BECAUSE some computer chess writters think they are the >same ;) I can't agree more with this, the main confusion comes from first confusing them into beeing the same :) >I have read that someone has written that Negascout is just another way of >implemention of pvs or vice versa. That's also my way of seeing it, reformulating PVS into a single function. >At first glance, they look quite similar: both are based on AlphaBeta, both use >aspiration search with zero window, both have to research if new value falls out >of this window. However, they differ each other in only small but important >detail: first move vs bestmove. >negascout: >1) Search with full window for the first move >2) Search with zero window for the rest moves (it means from the second move) >3) Research with full window if new value falls out of zero window >pvs: >1) Search with full window if the bestmove has not been found yet (or the alpha >has not been updated) >2) Search with zero window for the rest moves >3) Research with full window if new value falls out of zero window >In my experiment, pvs can help to save much more nodes than negascout. >I think Bruce Moreland did the best discription about pvs in his web. I think this difference is Bruce's own interpretation and does not represent the original PVS algorithm. I think that, in the official articles, both PVS and NegaScout use what you describe as "negascout" here. I might be wrong. It seems Bruce's modification is an attempt to integrate the aspiration-search assumption with PVS. This is interesting. Fabien.
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