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SEE on non-capture moves in main search
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H.G.Muller



Joined: 10 Mar 2006
Posts: 12753
Location: Amsterdam
PostPost subject: Re: SEE on non-capture moves in main search    Posted: Thu Mar 29, 2007 2:15 pm Reply to topic Reply with quote
OK, I see. I was thinking about a fixed-depth alpha-beta tree. But it is because of the extension/reduction policy.

Tord Romstad wrote:
But what happens if the score of the first move at a PV node suddenly drops by a big amount compared to the previous iterations? I think it might be a good idea to look for a good way to select a promising second move to search. One approach I have considered (but not yet tested) is to do an IID search with the first move removed from the move list at PV nodes where the score of the old best move drops a lot compared to the previous iteration.

It sounds like a good idea. I guess that the old PV move would disqualify itself anyway, as when you start the search at low depth its lower, but exact score would be satisfied from the hash table as it was already searched to higher depth.

I guess IID really should go like this:
1) Keep the depth, score and bound type for every move in the move list. When first entering the node, if hash and null move do not fail high, fill this from the hash.
2) reset the depth of all moves with upper-bound scores above the current alpha to -1, and their score to alpha.
3) As long (and as soon) as you have a move with a lower-bound score above beta, deepen that one. If the score remains good all the way, you are done.
4) Lacking such moves, look for the move with lowest depth. If that depth is the required depth, we are done. If not, and there are more of that depth, take the one with the highest score first.
5) if the depth is lower than required, search that move one deeper, with the current window (i.e. not upping alpha on any score above it that was not obtained at the currently requested depth or better!).
5) continue 3-5 until there are no more moves with depth below the requested one.

This is nearly how Joker's search works. (What lacks is that it does not reset the depth of moves with insufficiently sharp upper bounds.) It would pretty much solve the problem you sketch: If you were deepening evenly, and your PV move suddenly drops in score at depth d, you re-search all moves of which you are not yet sure at depth d-1 that they are no good, starting at d=0, in the hope to cheaply discover that there is one that might have some merit. The PV move will never be re-searched, as it already has an exact score at depth d. If none of the other moves at depth d-1 is able to beat alpha at depth d-1, there is little hope that they will be able to do so at depth d, and they will be searched to depth d in the order of their meaning-poor upper bounds (so that the ones we already know to be lousy for sure at least go in the end). But if some of them have scores above alpha at d-1, they are searched in the order of their scores, in the hope that they will not suffer the same drop as the old PV move.

Last edited by H.G.Muller on Thu Mar 29, 2007 2:19 pm; edited 1 time in total
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Subject Author Date/Time
SEE on non-capture moves in main search Gary Wed Mar 28, 2007 11:25 pm
      Re: SEE on non-capture moves in main search Robert Hyatt Thu Mar 29, 2007 1:17 am
            Re: SEE on non-capture moves in main search Tord Romstad Thu Mar 29, 2007 10:03 am
                  Re: SEE on non-capture moves in main search ed Thu Mar 29, 2007 1:34 pm
                        Re: SEE on non-capture moves in main search Sam Hamilton Fri Mar 30, 2007 12:07 am
                        Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 11:46 am
                  Re: SEE on non-capture moves in main search Robert Hyatt Thu Mar 29, 2007 9:35 pm
                        Re: SEE on non-capture moves in main search H.G.Muller Thu Mar 29, 2007 10:27 pm
                              Re: SEE on non-capture moves in main search Robert Hyatt Fri Mar 30, 2007 12:05 am
                                    Re: SEE on non-capture moves in main search H.G.Muller Fri Mar 30, 2007 6:50 am
                                          Re: SEE on non-capture moves in main search Robert Hyatt Fri Mar 30, 2007 9:27 pm
                                                Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 10:29 pm
                                                      Re: SEE on non-capture moves in main search Robert Hyatt Sun Apr 01, 2007 1:51 am
                                                            Re: SEE on non-capture moves in main search Tord Romstad Sun Apr 01, 2007 7:54 am
                                                                  Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 1:57 am
                                                            Re: SEE on non-capture moves in main search H.G.Muller Sun Apr 01, 2007 10:22 am
                                                                  Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 2:05 am
                                                                        Re: SEE on non-capture moves in main search H.G.Muller Mon Apr 02, 2007 12:31 pm
                                                                              Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 3:56 pm
                                                                                    Re: SEE on non-capture moves in main search Steven Edwards Mon Apr 02, 2007 4:44 pm
                                                                                          Re: SEE on non-capture moves in main search H.G.Muller Mon Apr 02, 2007 4:59 pm
                                                                                          Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 6:44 pm
                                                                                          Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 6:40 pm
                                                                                    Re: SEE on non-capture moves in main search H.G.Muller Mon Apr 02, 2007 4:53 pm
                                                Re: SEE on non-capture moves in main search H.G.Muller Sat Mar 31, 2007 8:38 am
                                                      Re: SEE on non-capture moves in main search Robert Hyatt Sun Apr 01, 2007 1:59 am
                                                            Re: SEE on non-capture moves in main search Tord Romstad Sun Apr 01, 2007 7:58 am
                                                                  Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 3:57 pm
                                                                  Re: SEE on non-capture moves in main search Peter Fendrich Mon Apr 02, 2007 5:19 pm
                                                                        Re: SEE on non-capture moves in main search Robert Hyatt Mon Apr 02, 2007 6:46 pm
                                                                        Re: SEE on non-capture moves in main search Tord Romstad Mon Apr 02, 2007 6:51 pm
                                                                              Re: SEE on non-capture moves in main search Peter Fendrich Mon Apr 02, 2007 7:53 pm
                                                                                    Re: SEE on non-capture moves in main search H.G.Muller Mon Apr 02, 2007 9:01 pm
                                                                                          Re: SEE on non-capture moves in main search Peter Fendrich Mon Apr 02, 2007 9:30 pm
                                                                                          Re: SEE on non-capture moves in main search H.G.Muller Tue Apr 03, 2007 8:46 am
                                                                                          Re: SEE on non-capture moves in main search Peter Fendrich Tue Apr 03, 2007 10:29 am
                                                                                          Re: SEE on non-capture moves in main search Robert Hyatt Tue Apr 03, 2007 9:23 pm
                                                                                          Re: SEE on non-capture moves in main search Tord Romstad Wed Apr 04, 2007 2:38 pm
                                                                                          Re: SEE on non-capture moves in main search Peter Fendrich Wed Apr 04, 2007 7:49 pm
                                                                                          Re: SEE on non-capture moves in main search Tony Tue Apr 03, 2007 10:54 am
                                                                                          Re: SEE on non-capture moves in main search Robert Hyatt Tue Apr 03, 2007 9:24 pm
                                                                                          Re: SEE on non-capture moves in main search H.G.Muller Tue Apr 03, 2007 9:29 pm
                                    Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 11:40 am
                              Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 11:54 am
                                    Re: SEE on non-capture moves in main search H.G.Muller Fri Mar 30, 2007 1:28 pm
                                          Re: SEE on non-capture moves in main search H.G.Muller Fri Mar 30, 2007 4:41 pm
                        Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 11:30 am
                              Re: SEE on non-capture moves in main search Uri Blass Fri Mar 30, 2007 11:50 am
                                    Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 10:32 pm
                              Re: SEE on non-capture moves in main search H.G.Muller Fri Mar 30, 2007 12:16 pm
                              Re: SEE on non-capture moves in main search Robert Hyatt Fri Mar 30, 2007 9:32 pm
                                    Re: SEE on non-capture moves in main search Tord Romstad Fri Mar 30, 2007 10:00 pm
      Re: SEE on non-capture moves in main search Mark Lefler Thu Mar 29, 2007 6:30 am
      Re: SEE on non-capture moves in main search H.G.Muller Thu Mar 29, 2007 9:28 am
            Re: SEE on non-capture moves in main search Tord Romstad Thu Mar 29, 2007 10:13 am
                  Re: SEE on non-capture moves in main search H.G.Muller Thu Mar 29, 2007 12:03 pm
                        Re: SEE on non-capture moves in main search Tord Romstad Thu Mar 29, 2007 12:39 pm
                              Re: SEE on non-capture moves in main search H.G.Muller Thu Mar 29, 2007 2:15 pm
                                    Re: SEE on non-capture moves in main search Zach Wegner Thu Mar 29, 2007 9:10 pm
                  Re: SEE on non-capture moves in main search Steven Edwards Thu Mar 29, 2007 2:18 pm
                  Re: SEE on non-capture moves in main search Rob Sun Apr 01, 2007 6:01 pm
      Re: SEE on non-capture moves in main search Gary Sun Apr 01, 2007 8:26 am
      Re: SEE on non-capture moves in main search Markoff Thu Apr 05, 2007 11:25 pm
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