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From: | Philippe Michel |
Subject: | Re: [Bug-gnubg] Errors in evaluation of races with backgammons |
Date: | Mon, 27 Feb 2012 23:06:05 +0100 (CET) |
User-agent: | Alpine 2.00 (BSF 1167 2008-08-23) |
On Mon, 27 Feb 2012, Joseph Heled wrote:
Using some python trickery it is possible to get the true backgammon figure. "true" here means that you always make the optimal move which minimises the probability of backgammon. The number is 40615026 / (36^5) = 0.6716982730973429 Now, nngnu gives those numbers for plies 0 to 5 0ply 0.6775242686271667 1 0.6775177717208862 2 0.6775177717208862 3 0.6775176525115967 4 0.6717002391815186 5 0.6716980934143066 which I am happy about, but it seems that *there is* some problem in gnubg, which gives different numbers for different plies.
This is because the pruning phase in gnubg is using only the race pruning net output (plus basic sanity checking). Adding the backgammons post-processing leads to the same numbers :
Win W(g) W(bg) L(g) L(bg) Equity Cubeful static: 1.000000 1.000000 0.677524 0.000000 0.000000 +2.677524 +2.677524 1 ply: 1.000000 1.000000 0.677518 0.000000 0.000000 +2.677518 +2.677518 2 ply: 1.000000 1.000000 0.677518 0.000000 0.000000 +2.677518 +2.677517 3 ply: 1.000000 1.000000 0.677518 0.000000 0.000000 +2.677518 +2.677517 4 ply: 1.000000 1.000000 0.671700 0.000000 0.000000 +2.671700 +2.671701 5 ply: 1.000000 1.000000 0.671698 0.000000 0.000000 +2.671698 +2.671699 I will commit the fix.
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