Author: Robert Hyatt
Date: 06:30:05 02/01/00
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On February 01, 2000 at 05:48:20, Tijs van Dam wrote: >On January 31, 2000 at 21:38:39, Robert Hyatt wrote: > >>On January 31, 2000 at 16:48:41, Tim wrote: >> >>>Crafty does not use(store and probe) hash table at root. >>>How about other programs? >>>Is there problem to use hash table at root? >> >> >>Suppose you look up the root position before you search a single move. What >>do you get back? A fail high? etc. There is really nothing useful to be >>gained by probing at ply=1, and exiting without searching a single move can >>cause some messy problems depending on how you write the code. In my case, >>I didn't want to exit without searching as that confuses some bookkeeping that >>I do.. > >I use hash at root for my program GKJunior. But I won't let the root search >fail high or low on the hash, just use an exact value with its "best move" or >use a move with not enough draft to search first. This way, a best move will >always be found at ply=1. I have no problems and the code is not messy. you just mentioned one messy detail. "no fail high or low". This means that for _every_ hash probe, you must be checking to see if you are at ply=1 before you do the fail high or fail low? All for no benefit at all. > >An advantage is that the search will continue very fast when the opponent makes >the same move as i was pondering, or to start pondering after making a move. >There is almost no delay, while crafty seems to take a few seconds to get to the >same PV as it had before the move was made. > I do this differently. If I complete a 12 ply search, and start to ponder, I ponder the 2nd move in the PV, I shift the PV two moves left to get rid of the move I made and the move i am pondering. I then start the search at old depth-1 since I already have the PV from old depth-2 done... >Greets, >Tijs
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