Author: Bruce Moreland
Date: 09:47:57 11/30/00
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On November 30, 2000 at 06:00:25, Tony Werten wrote: >On November 30, 2000 at 03:34:10, Scott Gasch wrote: > >>Hi again, >> >>The other day I posted about move ordering, tree size and SEE vs MVV/LVA. The >>response from experienced programmers was that a SEE was better than the naive >>MVV/LVA ordering, especially in the qsearch. So for the past couple of days >>I've been writing a SEE. It's based on crafty's swap code and understands >>pieces pinned to the king and xray attacks (pieces added to the attack/defend >>because of discovered attack). I have been through this code in a debugger and >>am about 99% sure it works fine. >> >>When I finally got around to testing the new SEE's effect on the search tree I >>was surprised to discover that it actually increased the tree size in all of my >>test position. Both Bob and Bruce mentioned that there could be significant >>qsearch node savings with a SEE... perhaps I misunderstood how to implement >>this. I'm simply doing the same thing I was with MVV/LVA: stop considering >>nodes when the value of a capture becomes negative. Since the list is sorted, > >I'm not really sure, but I'll give it a try. It seems that before you stopped >quiescence search when MVV/LVA gave a negative score. >If this is true, you will not get a smaller tree with SEE. What you did was >tossing out almost all captures. You can not get a smaller tree than that. ( >Well, if you search 8 ply, toss out anything deeper than 6 ply is about the >same) Unfortunately it's not correct. Using see will gave you a better quality, >but you have to search more nodes. > >Before you only searched upwards captures like BxR wich are always wins. >With see you search the same plus RxB, RxR, RxR. That's always more nodes. Yes, if that's what he is doing, that is the problem. QxN is often a great move, because the knight isn't protected. If he was throwing that out with his MVV/LVA, he just had a broken quiescent search before. If he was going into quiescent search in an even position where NxN RxN was possible, he was scoring this as +3. bruce
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