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/* gcompris - gcompris_alphabeta.c
*
* Copyright (C) 2000 Bruno Coudoin
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "gcompris.h"
/* gc_alphabeta returns the best value of evaluation functions */
/* set the bestChild to the index of child with this value */
/* maximize : TRUE if depth is maximize one, neither FALSE. */
/* treeGame : pointer on game to pass to others functions, */
/* bestChild : pointer on GList wich will contains list of indexes fo best plays. */
/* isLeaf : TRUE if game correspond to a Leaf of Tree. */
/* firstChild : return pointer on first child of a node. */
/* nextSibling : return pointer on next sibling of a node. */
/* heuristic : evaluation function of game. */
/* depth is max depth of recursion */
gint gc_alphabeta (gboolean maximize,
gpointer treeGame,
EvalFunction heuristic,
gint *bestChild,
FirstChildGameFunction firstChild,
NextSiblingGameFunction nextSibling,
gint alpha,
gint beta,
gint depth
)
{
gpointer child;
gint m, t, nextBest, index;
g_assert (depth >= 0);
child = firstChild(treeGame);
*bestChild = -1;
/* g_warning("gc_alphabeta %d %d %d", depth, alpha, beta); */
/* directly return value for leaf node*/
if ((!child) || (depth == 0)){
/* g_warning("gc_alphabeta %d returns %d bestChild %d", depth, heuristic(treeGame), *bestChild); */
return heuristic(treeGame);
}
index = 0;
if (maximize) {
m = alpha;
while (child){
t = gc_alphabeta (!maximize,
child,
heuristic,
&nextBest,
firstChild,
nextSibling,
m,
beta,
depth - 1
);
if (t > m){
m = t;
*bestChild = index;
}
if ( m >= beta){
/* g_warning("gc_alphabeta %d returns %d bestChild %d", depth, heuristic(treeGame), *bestChild); */
return m;
}
index++;
child = nextSibling(child);
}
/* g_warning("gc_alphabeta %d returns %d bestChild %d", depth, heuristic(treeGame), *bestChild); */
return m;
}
else {
/* minimize */
m = beta;
while (child){
t = gc_alphabeta (!maximize,
child,
heuristic,
&nextBest,
firstChild,
nextSibling,
alpha,
m,
depth - 1
);
if (t < m){
m = t;
*bestChild = index;
}
if ( m <= alpha){
/* g_warning("gc_alphabeta %d returns %d bestChild %d", depth, heuristic(treeGame), *bestChild); */
return m;
}
index++;
child = nextSibling(child);
}
/* g_warning("gc_alphabeta %d returns %d bestChild %d", depth, heuristic(treeGame), *bestChild); */
return m;
}
}
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