[Freeciv-Dev] Want calculation (Was:Re: flying AI (PR#1162))

[Gregory Berkolaiko <gberkolaiko@xxxxxxxxxxx>]

 --- "Ross W. Wetmore" <rwetmore@xxxxxxxxxxxx> wrote: 
> 
> This is used for veteran units. Obviously they are 40 somethings better
> than the standard unit build_cost, probably because rifleman are the
> prototypical unit and this is double the shield cost or something :-).

I thought it is used as the boat cost if we need the boat.

> To repeat a former caution though. There is a rationale for everything
> if you can hold onto your sanity long enough to figure it out. But
> these
> long involved calculations are not in themselves particularly important
> or useful. They attempt to mimic some human assessment process, but
> don't
> really cover the full spectrum, so accuracy is meaningless within a
> fairly broad range.

I disagree on "mimic some human assessment" issue.  It's an attempt to
code mathematically sound tactics IMHO.  Which is "to profit whatever we
do".  The human assessment is more "can I kill it somehow?" while the
code attempts at "will I profit if I try to kill it?" approach.

Possibly bigger difference is in general view on combat:
Human "here is the enemy, where is my Howitzer?" 
and AI "here is my howitzer, where is the enemy?"

But it is general philosophy and here is something concrete:
I managed to hold on to my sanity for long enough to at least partially
decode "want" calculation.  I was looking at the lines around
http://www.freeciv.org/lxr/source/ai/aiunit.c?v=cvs#L1411
(function find_something_to_kill)

Want = Operation_Profit * Amortization_Factor

where 

* Amortization_Factor is completely beyond me (but it's a function of the
estimated time length of the operation).

* Operation_Profit = Battle_Profit - Maintenance

where

* Maintenance 
  = (1 shield + Unhappiness_Compensation) * Operation_Time 
  (here unhappiness is from military unit being away from home)  

* Battle_Profit
  = Shields_Lost_By_Enemy * Probability_To_Win 
    - Shields_Lost_By_Us * Probability_To_Lose

That is Battle_Profit is probabilistic average.

In the calculation the probabilities enter approximately (and the
approximation is rather bad, but who cares).

Best,
G.

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