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[Bug-gnubg] Luck analysis, round-off error
From: |
Christopher D. Yep |
Subject: |
[Bug-gnubg] Luck analysis, round-off error |
Date: |
Tue, 19 Aug 2003 08:37:54 -0400 |
Windows XP, GUI version
Version 0.14-devel 1.1282 030818 (build Aug 19 2003)
After installing the above build I played a 64 pt. match, gnubg
intermediate vs. gnubg advanced.
Here are my luckanalysis settings (unchanged throughout the experiment):
set analysis luckanalysis plies 0
set analysis luckanalysis reduced 0
set analysis luckanalysis cubeful on
set analysis luckanalysis noise 0.000
set analysis luckanalysis deterministic on
Also my MET is the Snowie MET (also unchanged throughout the experiment).
Also note: all evaluations listed below are done with cubeful checker
evaluation and no noise (i.e. the 0-ply analysis is expert, the 2-ply
analysis world class).
1. I then analysed the match at 0-ply checker, 0-ply cube.
Luck adjusted result: Advanced: +17.63%
If I save the .sgf file, then re-open it, the luck adjusted result is then
reported as +17.66%. If I then Analyse - Clear Analysis - Match and redo
the analysis, it's back to 17.63% again. Is this round-off error?
I repeated the above several times (including closing and reopening gnubg
before opening the saved .sgf file). Each time the .sgf file is open/read,
gnubg reports +17.66%. Each time the analysis is actually performed
however, gnubg only reports +17.63%.
2. I then did Analyse - Clear Analysis - Match, and repeated the same
analysis with 1-ply checker (move filter = normal), 1-ply cube (move filter
= normal). I repeated this experiment several times as well.
Results: every time the analysis is actually performed, gnubg reports a
luck adjusted result of Advanced: +17.73%. Every time the file is actually
opened however, gnubg reports +17.75%.
3. Finally for completeness I did Analyse - Clear Analysis - Match, and
repeated the same analysis for 2-ply checker and cube (move filter = normal
for both). Now every time the analysis is performed gnubg reports a luck
adjusted result of Advanced: +33.57%, but when the file is actually opened
gnubg reports +33.60%. I repeated this step twice (it takes a long time
since it's a 64 pt. match) with the same results.
Note that my luckanalysis (and MET) settings did not change throughout the
experiment. The luckanalysis should have been done at 0-ply even when I
was analysing at 2-ply. Thus all 6 of these numbers (17.63%, 17.66%,
17.73%, 17.75%, 33.57%, 33.60%) should have been identical. However
the luck adjusted result reported during the 2-ply analysis is quite
different from the other luck adjusted results.
Are the changes between 17.63% and 17.75% due to round-off error? There
are 1437 moves in the file and since gnubg internally stores equities to 7
or 8 decimal places it seems unlikely that this much error could accumulate
in just 1437 moves. What about the 33.57% and 33.60% figures? I'm
guessing that gnubg is incorrectly calculating the luck adjusted result
using 1-ply evaluations (which are different than 0-ply evaluations and
just by chance are different by ~16% [33% - 17%] over the course of a very
long match).
I can send the .sgf files to anyone interested, but naturally I won't post
them to the mailing list.
Chris
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