There are still some bugs in the undo almost surely...

1 files changed, 27 insertions, 12 deletions

diff --git a/include/negamax.c b/include/negamax.c
index 757a648..16eba9a 100644
--- a/include/negamax.c
+++ b/include/negamax.c
@@ -108,39 +108,54 @@ negamax_generate(void) {
 	return result;
 }
 
+static enum WIN_TYPE w;
 
 static float
 negamax(const uint8_t cur_depth, float alpha, float beta,
 				const float colour) {
 	float value = -infty;
 
-	action_list_t *action_list = action_list_generate();
-	action_list_t *action = action_list;
+	action_list_t *list = action_list_generate();
 
-	while (action != NULL) {
+	for (action_list_t *node=list; node!=NULL; node=node->next) {
 		negamax_display_progress(cur_depth);
 
-		action_take(action);
-		if (cur_depth > 1) {
+		action_take(node);
+
+		// Somebody won?
+		if (ply >= 2*board_size - 3 && (w = check_win()) < 0xFF) {
+			if (w == WIN_ROAD_BLACK || w == WIN_FLAT_BLACK) {
+				value = colour*infty;
+				if (value > 0) {
+					// Always take the win for ourselves
+					action_undo(node);
+					if (cur_depth == negamax_search_depth)
+						action_to_ptn(node, negamax_ptn);
+					goto prune;
+				}
+			} else if (w == WIN_DRAW) value = 0; // Draw is fixed at neutral
+			else value = -colour*infty;
+		} else if (cur_depth > 1) {
+			// Recurse away from the leaves
 			value = fmax(value, -negamax(cur_depth - 1, -beta, -alpha, -colour));
 		} else {
-			value = fmax(value, colour*cnn1986_evaluate_black_win());
+			// Evaluate a leaf
+			value = fmax(value, colour * cnn1986_evaluate_black_win());
 		}
-		action_undo(action);
 
-		// alpha = fmax(alpha, value);
+		action_undo(node);
+
 		if (value > alpha) {
 			alpha = value;
 			if (cur_depth == negamax_search_depth)
-				action_to_ptn(action, negamax_ptn);
+				action_to_ptn(node, negamax_ptn);
 		}
 		if (alpha >= beta) break;
-
-		action = action->next;
 	}
 
-	action_list_free(action_list);
+	action_list_free(list);
 
+ prune:
 	return value;
 }