Author: Tom Kerrigan
Date: 10:26:51 05/05/00
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On May 05, 2000 at 11:16:34, Pat King wrote: >It seems clear to me that you need pretty good move ordering for PV to pay off >vs. plain AB. But how good? One could use only the pvmove[][] structure to >implement it (although I use just the hash, and probe it to find the PV). Is >this enough to make it pay? Are history tables and killer moves more effective >w/ PV than AB? > >Thanks. > >Pat I think you're confusing PV and PVS, which are two totally different things. PV is the Principal Variation, i.e., your best line. This is stored in the pvmove[][] array that you mention, and can be used with any type of search, including plain old alpha-beta. You obviously want to order the PV high at the start of a search. Assuming that the PV will be stored in your hash table is just fine, as long as you have a reasonably large hash table and a good replacement scheme. PVS is Principal Variation Search, which (I believe) is also known as null-window search. It's a method used to decrease the size of the alpha-beta windows within the search. It really has nothing to do with Principal Variations, except at the conceptual level, because it requires good move ordering to be effective. -Tom
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