Author: Robert Hyatt
Date: 15:35:56 09/06/04
Go up one level in this thread
On September 06, 2004 at 10:48:00, Stuart Cracraft wrote: >On September 06, 2004 at 04:47:12, Alessandro Scotti wrote: > >>On September 05, 2004 at 22:12:35, Stuart Cracraft wrote: >> >>>I walk the PV until there is no further position. No limit. This can then >>>either be left in the hash table if you don't clear between searches >>>but like Bob, you should keep the PV entries and restore them in the >>>hash table before the next search whether or not you table-clear due to >>>potential changes. >>> >>>I don't do this. It's a simple fix. I don't know why I've delayed putting >>>it in. >> >>I don't either. But since I get my PV from the hash table, it's already there. > >Mine is already in there as well so I don't see why Bob said to >store it in the hash table after the last iteration unless Crafty uses >some different method to record the PV and has to store it in the hash >table prior to the next iteration. Why wouldn't it be in there already? >Does Crafty clear the hash table between moves?. How do you _guarantee_ that the PV won't get overwritten as you search moves _after_ searching the PV? The answer is, "you can't guarantee that." Every program I have seen has problems with incomplete PVs and PVs with an occasional bogus move for that very reason.. The only solution is to back the PV up along with the score... And even then you can get a short PV due to an EXACT hash hit along the PV. > >For the record, I clear the hash table between moves but only because >I do suite testing exclusively -- I plan to make this a flag based >on whether I am testing (clear hash table between each test position) >or playing a normal game (don't clear hash table.) > >In the latter case, with the structure of the program, it walks the pv >after each iteration to print out the pv. Hence it is already in the hash >table at the start of the next iteration, so no need to add it. Not sure >what circumstance would ever require it to be added. > >This is why I haven't added it. Structurally it looks unsound for my program.
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