[Freeciv-Dev] Re: (PR#12734) A new, fast and greedy CM implementation

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=12734 >

Per I. Mathisen wrote:
> <URL: http://bugs.freeciv.org/Ticket/Display.html?id=12734 >
> 
> I was tired of slow AI games, so I decided to handle the root of all evil
> - the city management code. I wrote my own CM from scratch, and stuffed it
> in the bottom of city.c. At approx 300 lines of code, it is not very big.

Putting it into city.c is the wrong thing I think.  It should stay in 
cm.c, safely hidden behind the CM interface.  If we need to change that 
interface, we should.  We should already change the interface a bit to 
allow partial placements (placement of one new worker without 
redistributing any existing ones).

> In a very difficult, very large savegame that I used for reference, CM did
> 26% better in finding optimal solutions according to the scoring test I
> made. The greedy function was, however, 154 times faster.

The current CM is exponential, more or less.  A simple greedy algorithm 
would be linear I think.  So it will be particularly faster on large 
cities.  And if you can find an even larger city it will be much faster 
than that.

> If you want to measure for yourself, change "#if 0" to "#if 1" in
> server/cityturn.c; if you want more comments on the design, see the huge
> function header comment on the greedy function itself.

You've made some interface changes to other parts of the code too, I 
notice.  Are these changes related or separate?

-jason