Author: Andrew Williams
Date: 11:06:27 11/28/00
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On November 28, 2000 at 12:52:57, Scott Gasch wrote: >Hi, > >I posted a couple of messages about move ordering yesterday and wanted to share >some results from my (limited) testing. I ended up implementing the suggested >"apparently losing captures" (MVV/LVA) after all others order. In one test >position this resulted in a tree 200k nodes larger at 8 ply but in two others it >resulted in a marginally smaller (under 40k nodes) tree at 8 ply. I will do >more testing on this matter but it may be a moot point because I intend to write >a SEE pretty soon. > >I also did some experimenting with ordering captures that take the last moved >enemy piece. At low search depth this seems to make some difference but at >higher depth this heuristic actually grew the tree in all three test positions > I tried. > >I also did some playing with history weight and settled on hist[x][y] += (2 << >depth). I use history[whoseTurn][frsq][tosq] += (depthremaining*depthremaining) I have a separate table for white and black. Every few plies I divide this number back by a lot (can't remember how much or how often). > My numbers (this is total nodes searched until ply x including plys >1..x-1) for d2d4 d7d5 e2e4 e7e5 are currently: > PostModernist Monsoon 1 145 45 2 214 621 3 864 3725 4 3330 14146 5 14057 38694 6 38838 183449 7 120729 598020 8 294806 1286875 This is with all my normal extensions on. > >I am doing null move (R=2/3 depending on remaining and normal futility pruning >with a slightly larger than safe window on frontier nodes and in qnodes. I've >read about extended futility pruning and razoring too. I'd be interested in >other ideas to cut down the tree search size... be they other move ordering >heuristics or other pruning methods that are reasonably safe. How do the nodes >searched in the position given compare to other engines? > >Thanks again, >Scott I try two killers from the current ply and then two from two plies ago. The last time I isolated this and tested it it was a very small win. Other than that, my move ordering is hash, winning captures, equal captures, killers this ply, killers from two plies ago, then non-capturing moves then losing captures. Looking at that list, I think I'll test killers before equal captures, though I'm sure I'd have tried that before. In any case, only the first eight moves at a node are ordered (maybe it's not eight). The assessment of a capture is done by a SEE. Andrew
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