Re: [Gtkboard-devel] help writing a game

[Arvind N. <ran...@gm...>]

Hi!

Well first of all its about a year since I worked on gtkboard, so I
might not remember all the details right, but anyway...

On 26 Sep 2004 23:37:23 +0100, nelson <gn...@ce...> wrote:
> Hello :), Im writing a game for gtkboard, is an entertainment pencil and
> paper game,Im firstly trying to write the Machine to Human type, but Im
> a bit confused how to connect my machine-turn C code to the game_eval
> and  game_movegen hooks, you know, I have my own c algorithm for the
> machine to choose its move from the existent board, but there is no an

The game_eval and game_movegen functions assume that you want to do
game tree evaluation (alpha-beta and generalizations thereof; see
http://en.wikipedia.org/wiki/Alpha-beta_pruning in case you are not
familiar with those algorithms). game_eval and game_movegen are hooks
for the eval and movegen algorithms in minimax search.

However, I think you're not using minimax, so you don't want to use
those. There's a game_search function, which lets you search the
position yourself and return the best move. If game_search is
non-null, it will be called and minimax/alpha-beta will not be
executed.

> easy hook where only put the position chosen by the Machine (that
> position computed by a function of mine)...instead it seems gtkboard
> forces me to use its functions for searching and calculating new
> movements (game_eval and game_movegen), that sure are more powerful and
> faster that my own but they are not well documented and I cant find out
> how to use them. Questions about that:
> 
> - Is there an easy hook where to put the machine move computed by me
> (avoiding game_eval and game_movegen)?
> 
> - What value Am I supposed to put on the float *eval argument?
> 
> - How Can I control the turn flow ?, because in my game a human can make
> three moves in 3 clicks (3 events) and then pass the turn to the
> machine,but it seems gtkboard passes the turn between human and machine
> automatically after a one succesful move...

Ah! As far as the program is concerned, when you complete one "move",
the other player gets the turn. So you are supposed to pretend that a
move has not been completed (by returning 0 in X_getmove() rather than
1) and still update the board on the screen. There's some ugly stuff
like RENDER_* to do that, but not difficult. Lots of games do such
things, such as mastermind.

Feel free to ask me again if something was not clear.

> My game also will have levels of difficulty (machine thinking a bit
> smarter).
> 
> Explaining of the game:
> 
> Initial Board:
> 
> X X X X X X X
>   X X X X X
>     X X X
> 
> Simple Rules:
> Loose the one who removes the last piece.
> In a turn, you can only remove pieces from one row, but you can remove
> as many pieces as you want, for example the entire row.

In other words: Nim. Yes, you definitely don't want to use alpha-beta
for that one :)

Fascinating stuff though. I spent about two months reading up the
Conway Berlekamp theory and I loved every bit of it. It would be nice
to see some Nimlike games in gtkboard.

Good luck

Arvind
> PD: Thanks and sorry for the long text...
> 
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