[freeciv-ai] Re: Approximate win_chance

[Gregory Berkolaiko <Gregory.Berkolaiko@xxxxxxxxxxxx>]

On Thu, 25 Apr 2002, Raimar Falke wrote:

> On Wed, Apr 24, 2002 at 08:17:47PM -0400, Ross W. Wetmore wrote:
> > At 02:02 PM 02/04/24 +0200, Raimar Falke wrote:
> > >
> > >AFAIK the current win_chance isn't an approximation but returns the
> > >exact value. Or do I'm mistaken about that?
> > 
> > If I am not mistaken, you cannot compute the exact value since that is
> > determined randomly. 
> 
> > And if you are only estimating the chance
> 
> This is what is done.
> 
> > , then "exactness" is not a particularly hard criteria - certainly
> > not the determining one.
> 
> Yes the wording was bad.

Don't you fret, the wording is perfect.  The win_chance gives exact value 
for the probability to win the encounter.

> > [...]
> > >> > Bottom line 2: we have to carefully select the set of values we test
> > >> > the approximation against. Best would be the whole possible set of
> > >> > values. Or a real (not by simulation) mathematical calculation of the
> > >> > errors we have to expect.
> > >> 
> > >> Not asking for much are you?
> > >
> > >As I said this would be the ideal solution. If the current win_chance
> > >returns the correct value we have to have an estimation of the error
> > >which a new win_chance will produce.
> > 
> > I think the estimations have been done. They seem to indicate that the
> > 5th power solution is better than the current 2nd power one and almost
> > indistinguishable from the more explicit estimation of chances.
> 
> > Since none of this really affects anything critical in the game, the 
> 
> And this is a question which is still unanswered for me: How do you
> (the ai developers) that a particular code construct needs the "exact"
> value (as returned by win_chance) and when does it can cope with an
> approximation (which has an average/maximal error of something)? I
> suspect that you don't do this decision based on hard facts.

Hard facts are hard to come by.  Things are not black and white, 
especially in a game with such complicated rules.

You think and then you experiment.  My dissatisfaction with the performace 
of the current approximation comes from my observation described in
        http://arch.freeciv.org/freeciv-dev-200203/msg00741.html
The decision made by the AI is not a critical one (a missed opportunity 
to inflict some damage) and if a better approximation can reduce the 
number of such non-critical errors without pushing the time up, it is 
good.  

But all such things are rather subjective...

G.