[Freeciv-Dev] Re: freeciv2 kernel,modules and rulesets

[Andrew Sutton <ansutton@xxxxxxx>]

On Sunday 02 December 2001 12:06 pm, you wrote:
> about objects in c...
>
> say we have map and each tile is object with information about terrain and
> special, possibly containing seat (object) and possibly containing units
> (objects).

> it is not so bad, in fact it could be done even better than i did here, and
> you have no c++ bloat ;p.

actually it is bad. you're automatically assuming that those pointers will be 
non-null, and at some point they won't be. it's not safe programming. it's a 
poor equivilancy.

oh... don't forget, your tile is now 160 bytes. assuming a map of only 32 by 
32, that comes to a total of... 160 KB. and that's for a small map. using 
c++, you'd lose all the function pointers (reduce to 64 bytes).

besides, you're missing something else too. maps are sparsely populated. to 
assign a unit stack to every tile is just a waste. a more appropriate (and 
equivilantly fast) implementation would be to store the unit stacks elsewhere 
and map them by the coordinates. i know it's not quite as elegant (or easy), 
but it's better on the footprint.

make the association of a unit stack external to the tile and you come up 
with a 32 byte tile.

the seat would probably follow the same rules as the unit stack. remove this, 
and your tile is empty. of course, it will contain a terrain indicator, but 
you didn't write that so i'm not adding it.

> you got me wrong. when you will put each type of unit into separate module,
> that means you will also in that module teach AI how to cope with that type
> of unit, if you are so modular, won't you? otherwise AI will panic and cry
> and you will be out of luck.

the current proposal isn't to put units into different modules... just 
capabilties. the unit is still a single class. the unit _will_ have to know 
how to cope with capabilities, but again, it has to in freeciv1. add a new 
capability, the ai has to learn it.

> everything? that is? iirc you mentioned only move rate.

did you want a complete description of every capability i can think of? 
that'd be a long email. besides, i'm actually working on this description 
off-line.

> now define what exactly will be kernel and what it will provide and what's
> so cool with microkernel pattern when used for freeciv.

what the kernel is is a tough question, as i only know as i think about 
things. to start with it is the game manager. the kernel understands how to 
load modules to get data. it understands how to create a game based on a 
ruleset (combine module data into understandable game form). it understands 
the basic protocol of the game, and is capable of enacting it. it maintains 
the world map, all the units, all the cities and all the players. it provides 
a player api for human and computer players and it provides an admin api 
allowing the game to be administrated or changed on the fly. it also has an 
extension requiring players be clients of the game server.

the microkernel pattern is what it is. a commonly recurring architectural 
pattern that is used to separate specific functionality or data from a core 
that could really care less about specifics.

> /me counts...

windows, linux, qt, gnome, kde, COM, corba, java beans, c#, DCOM, DCE, the 
OSI stack to some percentage, apache, etc, etc.

> /me stops counting bored.
>
> yes, i like modularization too, i'm using to write usually highly
> modularized software, however i soon learned that everything, even
> modularization, has its limits, and i think having separate module for each
> unit is above that limit. so please can you be concrete, which modules do
> you expect to see?

since we've only talked about unit capabilities, that's all i have to go on 
so far. a core module that provides the most common, basic unit capabilities 
(move, sentry, fortify, pillage). a civ module that provides civ extensions 
to the capability list. possibly a masters of magic module that provides MOM 
capabs. possibly an alpha centauri module that provides AC capabs. questions?

andy