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## [Bug-gnubg] Proposal - Luck rating

 From: Massimiliano Maini Subject: [Bug-gnubg] Proposal - Luck rating Date: Mon, 6 Jul 2009 11:37:57 +0200

Hi all,

2 details about "luck rating" computation (Go to bed, ..., Go to Vegas).

1. Luck is computed for each player independently: this leads to situations where
players are both very lucky (or very unlucky). Despite this being mathematically
understandable, the average user probabaly expects a "differential rating":
when player A has been "very lucky", he expects player B to be "very unlucky"
(zero sum).

Said otherwise, in matchplay, if player A and Player B Total Luck (MWC) are
+10%/+10% or +20%/+20%, the luck rating will be (let's say) "lucky/lucky" and
"very lucky/very lucky" respectively, but the average user probably expects
"none/none".

2. Looking into the code it seems to me that the luck rating for each player is
computed from the normalized luck rate. This does not make much sense to me.

The reference value to look at in order to understand who has been lucky is the diff
between the two players in Total Luck (in MWC for match, in Points for money).

The normalized luck (and luck rate) "factors out" the cube value/score (score
considerations are somehow factored out by EMG).

In matchplay, imagine a situation where a very long match goes up to DMP without
any particular luck for the two players. Then , at DMP bearoff, one roll a super joker
and wins. In terms of Total Luck this will appear clearly (like a +50% in MWC), but in
normalized luck this will not. The same situation in a much shorter match, despite
having the same total luck (+50%) could have a "Go to Vegas" rating instead of
a "lucky" or a "none" rating.

* For player A, take his total luck (in MWC for match, in Points for money) and subtract
player B's total luck: let's call this Net Luck. Of course NetLuck(A)+NetLuck(B)=0.

* Compare the actual result with the net luck and see which share of the actual result
is due to the net luck.

* For money, for player A:
Actual Res                Net Luck                Ratio                        Rating
+2                        +2                        +100%                -->        Very Lucky
+2                        +1                        +50%                -->         Lucky
+2                        +0                        +0%                -->         None
+2                        -1                        -50%                -->        Unlucky
+2                        -2                        -100%                -->        Very Unlucky

*For match, actual result is either +100% or -100%, do the same computations and apply
the same table to convert from the ratio to the rating.

I have no idea about how to convert the ratios into meaningful ratings, figures above are
just to illustrate.

MaX.