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Subject: Re: Experimentation with move ordering

Author: Vincent Diepeveen

Date: 11:51:10 11/28/00

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On November 28, 2000 at 12:52:57, Scott Gasch wrote:

output diep single cpu after 1.e4,e5 2.d4,d5:

150 mb hash
R=3
No other pruning.
Using PVS of course initial window -infinite,infinite
other windows work for my draughtsprog but not for
my chessprog.

00:00 27 (0) 1 -0.00 e4xd5 Qd8xd5 d4xe5 Qd5xe5 Bf1-e2
00:00 31 (0) 1 0.01 d4xe5 d5xe4 Qd1xd8 Ke8xd8
00:00 49 (0) 1 0.01 Ng1-f3 d5xe4 Nf3xe5
00:00 76 (0) 1 0.07 Nb1-c3
00:00 257 (0) 2 0.06 Nb1-c3 Nb8-c6 d4xe5 d5xe4 Qd1xd8 Ke8xd8
00:00 991 (0) 3 0.06 Nb1-c3 Nb8-c6 d4xe5 d5xe4 Qd1xd8 Ke8xd8
++ d4-e5
00:00 1660 (0) 3 0.49 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3
00:00 3764 (0) 4 0.49 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3
00:00 9851 (0) 5 0.06 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Nb8-c6
00:00 29220 (0) 6 0.27 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Nb8-c6 Bc1-f4
00:01 71305 (0) 7 0.22 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Bc1-g5 f7-f6 e5xf6 g7xf6 Bg5-e3

00:04 186666 (0) 8 0.56 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Nb8-c6 Bc1-f4 Bc8-f5 Bf
1-c4
00:10 442847 (0) 9 0.43 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Nb8-d7 Bc1-g5 Bf8-e7 Bg
5xe7 Ng8xe7 Ra1-d1 Kd8-e8
00:22 969920 (0) 10 0.46 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Nb8-c6 Bc1-f4 Bc8-f5 B
f1-c4 Kd8-e8 e5-e6
01:16 3219133 (0) 11 0.62 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Kd8-e8 Nc3xe4 Bc8-f5
Bf1-b5 c7-c6 Bb5-d3 Nb8-d7
02:19 6124647 (0) 12 0.55 d4xe5 d5xe4 Qd1xd8 Ke8xd8 Nb1-c3 Nb8-c6 Bc1-f4 Bc8-f5
O-O-O Kd8-e8 Nc3-b5 Ra8-c8 e5-e6 f7xe6 Bf4xc7

>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).  My numbers (this is total nodes searched until ply x including plys
>1..x-1) for d2d4 d7d5 e2e4 e7e5 are currently:
>
>1. 45
>2. 621
>3. 3725
>4. 14146
>5. 38694
>6. 183449
>7. 598020
>8. 1286875
>
>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

Using less pruning i need 10 times less nodes.

>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



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