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Revisiting Check Extensions
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Mark Lefler



Joined: 30 Mar 2006
Posts: 1162

PostPost subject: Revisiting Check Extensions    Posted: Thu Jun 07, 2007 9:25 am Reply to topic Reply with quote

Most programs I have seen seem to extend checks exactly one full ply. Some also extend one reply to checks another full ply (or sometimes less). A very few use an extession of 3/4 a ply. In my continuing experiments in my program, I have tried to come up with different criteria, and in testing they seem to help.

First I divide moves into capture and promotions, or non captures.

For promotions/captures, I use the results of an SEE to determine if the piece moving is being lost. Losing captures get a reduced extension (1/4 a ply to 1/2 a ply seems OK). Winning and equal captures get a full ply extension. I have also experimented with losing up to a pawn or material; getting the full ply extenion. Also, i have epxerimented with varying the extnsion depending on if it is a PV node (non-PV nodes get a lesser extension, but if they become PV nodes, get extended a full ply).

For non-captures, I do something similar (of course, the move is either equal or losing). Losing captures get a smaller extension.

My best tests so far suggest moves losing more than 1.5 pawns of material get no extension. Moves losing less material get 1/4 to 1/2 a ply, and winning or equal moves get a full ply. Ptrobably winning capture checks deserve more than a ply but I have not done enough testing to know for sure.

The goals of all of this is to shape the search tree, so moves with a higher probability of being best have more search under them, and moves likely to be bad, samller trees.

Has anyone revisited this issue, and is there something better than "always a full ply"?

Mark
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Display posts from previous:   
Subject Author Date/Time
Revisiting Check Extensions Mark Lefler Thu Jun 07, 2007 9:25 am
      Re: Revisiting Check Extensions Uri Blass Thu Jun 07, 2007 10:19 am
            Re: Revisiting Check Extensions Tord Romstad Thu Jun 07, 2007 10:33 am
                  Re: Revisiting Check Extensions Uri Blass Thu Jun 07, 2007 10:59 am
                        Re: Revisiting Check Extensions Uri Blass Fri Jun 08, 2007 8:37 am
                              Re: Revisiting Check Extensions ed Fri Jun 08, 2007 9:40 am
                                    Re: Revisiting Check Extensions Uri Blass Fri Jun 08, 2007 10:06 am
                  Re: Revisiting Check Extensions José C. Martínez Galán Thu Jun 07, 2007 11:01 am
                  Re: Revisiting Check Extensions H.G.Muller Thu Jun 07, 2007 11:59 am
            Re: Revisiting Check Extensions Mark Lefler Thu Jun 07, 2007 1:05 pm
      Re: Revisiting Check Extensions Robert Hyatt Fri Jun 08, 2007 3:25 pm
            Re: Revisiting Check Extensions Tony Fri Jun 08, 2007 3:50 pm
                  Re: Revisiting Check Extensions Robert Hyatt Fri Jun 08, 2007 4:03 pm
                        Re: Revisiting Check Extensions Tony Fri Jun 08, 2007 7:28 pm
            Re: Revisiting Check Extensions Mark Lefler Sat Jun 09, 2007 8:04 pm
                  Re: Revisiting Check Extensions Robert Hyatt Sat Jun 09, 2007 9:59 pm
                        Re: Revisiting Check Extensions Mark Lefler Sun Jun 10, 2007 7:34 am
                              Re: Revisiting Check Extensions Uri Blass Sun Jun 10, 2007 7:46 am
                              Re: Revisiting Check Extensions Robert Hyatt Sun Jun 10, 2007 3:25 pm
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