> On 11/13/07, jorma kala <address@hidden>
wrote: > Hi,
> how is the total error rate and the per move error rate exactly calculated?
> Is it just the average difference in MWC of each unforced move with
> respect to the MWC of the optimal move?
> Thanks.
> jorma
Hi Jorma,
I'll try to explain, somebody with better insight
please correct if wrong.
Errors are measured in terms of equity difference
of your move with respect to the optimal move (according to the currelt level
of play, e.g. world class).
If you don't normalize the equities, the same error
could have a different magnitude depending on the cube value (for money sessions)
or depending on the cube value and the score (for matchplay). Thsi is of course inconvenient, hence the normalization. In money games, it's enought to ignore the value of
the cube. For matchplay it's a bit more complicate since you
have to consider the match equity table and EMG (Equivalent to Money Games)
equities are used. They are computed by linear interpolation (and extrapolation)
against the value of a simple win and the value of a simple loss
(assumed to be +1 and -1) at the current cube value. They are described
here : http://www.bkgm.com/gloss/lookup.cgi?equivalent+to+money+game+equity
Example: at some point in a match you have exactly
50% mwc. A simple loss costs you -15% mwc (this is a normalized equity of -1) for
35%mwc, and a simple win gives you +15% mwc (this is a normalized equity of
+1) for 65% mwc. Now you can draw a line between the points (35%,-1)
and (65%,+1) to obtain the conversion between mwc and EMG equities. An error that costs you 7.5%mwc will correspond to
((+1-(-1))/(65%-35%)) * 7.5% = (2/30%) * 7.5% = 0.500: this means that this error
was half bad as losing the whole game.
In general, an error with an EMG equity of 0.100 (quite
a big one) will correspond to a small error in terms of mwc (e.g.
0.1%) in the very first games of a long match (e.g. 0-0 to 21 pts) but the
same EMG equity of 0.100 could well correspond to 5% or more in the last game
of a match (e.g. double match point).
The total error is just the sum of all the individual
errors. As explained by Christian then, the per move error
(rate) is cumputed dividing the total value by the number of unforced
moves (this is specific to gnubg, Snowie divides by the number of moves, forced
and unforced).
Because of that, the gnubg error rate is more severe
than the Snowie one (i.e. higher).