[Freeciv-Dev] Re: [RFC] Caching AI values

[Gregory Berkolaiko <Gregory.Berkolaiko@xxxxxxxxxxxx>]

On Tue, 19 Mar 2002, Tony Stuckey wrote:

> On Tue, Mar 19, 2002 at 02:47:28PM +0000, Gregory Berkolaiko wrote:
> > > There is another solution possible:
> > >  3. Update the value whenever this is necessary
> > 
> > You probably mean "whenever environment changes".  It is a very good 
> > approach.  But again there are arguments against it:
> > - too complicated: go trace all events which lead to "cnahge in 
> > environment"
> > - you might be doing all this in vain --- how do you know that these 
> > values will ever be accessed?
> > 
> > To implement 3 we would have to rewrite half of Freeciv to be event-driven 
> > system.
> 
>       My gut says that this would really only have to be re-evaluated
> when a unit is killed.  Of course, I might be thinking a bit too much in my
> preferred turn-based paradigm, where targets don't move out from under you
> while you try to figure out how to kill them.

That might be right, but let's have a look at the overall picture:
1. Unit A thinks about moving to city C to kill things around.  The number 
of things to kill around C is calculated and recorded in struct city C.
----
2. we are doing other stuff, but whenever we kill a unit, we have to 
figure out if it was counted in the targets_around_C and if it was, 
subtract its value
----
3. Now unit B thinks about moving to city C and it can use the up-to-date 
number of targets around.

I think that doing part 3 is technically difficult.  I guess we would need 
to create a list of cities for which we counted targets_around, together 
with max distances at which the targets were.  Then when we have a dead 
unit, we iterate around it to see if there are any cities from the list in 
the neighbourhood.  Sounds very much like fog-of-war, only maybe harder.

Undoubtedly this is how the things should be done.
But I am not keen on doing it right now.

I think time approach would perform quite well (on average).

G.