From 6f996b193400195c651c2d5a9cc1b721d979ad39 Mon Sep 17 00:00:00 2001
From: Jean-loup Gailly <jloup@gailly.net>
Date: Sat, 6 Aug 2011 19:05:32 +0200
Subject: [PATCH] uct_pass_is_safe(): force minimum number of playouts

This allows pass when it is the only sensible move (all other moves lose).
Bug reported by Michael Williams.
---
 uct/search.c | 25 +++++++++++--------------
 uct/uct.c    |  5 +++--
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/uct/search.c b/uct/search.c
index 7fc035e..c66cc16 100644
--- a/uct/search.c
+++ b/uct/search.c
@@ -479,20 +479,17 @@ uct_search_result(struct uct *u, struct board *b, enum stone color,
 	}
 
 	/* If the opponent just passed and we win counting, always
-	 * pass as well. */
-	if (b->moves > 1 && is_pass(b->last_move.coord) && b->rules != RULES_STONES_ONLY) {
-		/* Make sure enough playouts are simulated. */
-		while (u->ownermap.playouts < GJ_MINGAMES)
-			uct_playout(u, b, color, u->t);
-		if (uct_pass_is_safe(u, b, color, pass_all_alive)) {
-			if (UDEBUGL(0))
-				fprintf(stderr, "<Will rather pass, looks safe enough; score %f>\n",
-					board_official_score(b, NULL) / 2);
-			*best_coord = pass;
-			best = u->t->root->children; // pass is the first child
-			assert(is_pass(node_coord(best)));
-			return best;
-		}
+	 * pass as well. For option stones_only, we pass only when there
+	 * there is nothing else to do, to show how to maximize score. */
+	if (b->moves > 1 && is_pass(b->last_move.coord) && b->rules != RULES_STONES_ONLY
+	    && uct_pass_is_safe(u, b, color, pass_all_alive)) {
+		if (UDEBUGL(0))
+			fprintf(stderr, "<Will rather pass, looks safe enough; score %f>\n",
+				board_official_score(b, NULL) / 2);
+		*best_coord = pass;
+		best = u->t->root->children; // pass is the first child
+		assert(is_pass(node_coord(best)));
+		return best;
 	}
 	
 	return best;
diff --git a/uct/uct.c b/uct/uct.c
index baee743..06f933f 100644
--- a/uct/uct.c
+++ b/uct/uct.c
@@ -106,8 +106,9 @@ dead_group_list(struct uct *u, struct board *b, struct move_queue *mq)
 bool
 uct_pass_is_safe(struct uct *u, struct board *b, enum stone color, bool pass_all_alive)
 {
-	if (u->ownermap.playouts < GJ_MINGAMES)
-		return false;
+	/* Make sure enough playouts are simulated to get a reasonable dead group list. */
+	while (u->ownermap.playouts < GJ_MINGAMES)
+		uct_playout(u, b, color, u->t);
 
 	struct move_queue mq = { .moves = 0 };
 	dead_group_list(u, b, &mq);
-- 
2.11.4.GIT