From 1b27436c39fe35cf57e9c9dd88763120bc3122ca Mon Sep 17 00:00:00 2001
From: Jean-loup Gailly <jloup@gailly.net>
Date: Thu, 30 Dec 2010 20:02:06 +0100
Subject: [PATCH] UCT engine: change virtual_loss from bool to int

---
 uct/internal.h | 2 +-
 uct/uct.c      | 8 +++++---
 uct/walk.c     | 8 ++++----
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/uct/internal.h b/uct/internal.h
index 64614a4..0afe868 100644
--- a/uct/internal.h
+++ b/uct/internal.h
@@ -51,7 +51,7 @@ struct uct {
 		TM_TREE, /* Tree parallelization w/o virtual loss. */
 		TM_TREEVL, /* Tree parallelization with virtual loss. */
 	} thread_model;
-	bool virtual_loss;
+	int virtual_loss;
 	bool pondering_opt; /* User wants pondering */
 	bool pondering; /* Actually pondering now */
 	bool slave; /* Act as slave in distributed engine. */
diff --git a/uct/uct.c b/uct/uct.c
index b37a749..49820b0 100644
--- a/uct/uct.c
+++ b/uct/uct.c
@@ -538,7 +538,7 @@ uct_state_init(char *arg, struct board *b)
 
 	u->threads = 1;
 	u->thread_model = TM_TREEVL;
-	u->virtual_loss = true;
+	u->virtual_loss = 1;
 
 	u->fuseki_end = 20; // max time at 361*20% = 72 moves (our 36th move, still 99 to play)
 	u->yose_start = 40; // (100-40-25)*361/100/2 = 63 moves still to play by us then
@@ -741,18 +741,20 @@ uct_state_init(char *arg, struct board *b)
 					/* Tree parallelization - all threads
 					 * grind on the same tree. */
 					u->thread_model = TM_TREE;
-					u->virtual_loss = false;
+					u->virtual_loss = 0;
 				} else if (!strcasecmp(optval, "treevl")) {
 					/* Tree parallelization, but also
 					 * with virtual losses - this discou-
 					 * rages most threads choosing the
 					 * same tree branches to read. */
 					u->thread_model = TM_TREEVL;
-					u->virtual_loss = true;
 				} else {
 					fprintf(stderr, "UCT: Invalid thread model %s\n", optval);
 					exit(1);
 				}
+			} else if (!strcasecmp(optname, "virtual_loss")) {
+				/* Number of virtual losses added before evaluating a node. */
+				u->virtual_loss = !optval || atoi(optval);
 			} else if (!strcasecmp(optname, "pondering")) {
 				/* Keep searching even during opponent's turn. */
 				u->pondering_opt = !optval || atoi(optval);
diff --git a/uct/walk.c b/uct/walk.c
index 1dc42e4..1ded011 100644
--- a/uct/walk.c
+++ b/uct/walk.c
@@ -523,7 +523,7 @@ uct_playout(struct uct *u, struct board *b, enum stone player_color, struct tree
 		 * other threads from visiting this node in case of multiple
 		 * threads doing the tree search. */
 		if (u->virtual_loss)
-			stats_add_result(&n->u, tree_parity(t, parity) > 0 ? 0 : 1, 1);
+			stats_add_result(&n->u, node_color == S_BLACK ? 0.0 : 1.0, u->virtual_loss);
 
 		assert(n->coord >= -1);
 		if (amaf && !is_pass(n->coord))
@@ -652,10 +652,10 @@ uct_playout(struct uct *u, struct board *b, enum stone player_color, struct tree
 end:
 	/* We need to undo the virtual loss we added during descend. */
 	if (u->virtual_loss) {
-		int parity = (node_color == player_color ? 1 : -1);
+		floating_t loss = node_color == S_BLACK ? 0.0 : 1.0;
 		for (; n->parent; n = n->parent) {
-			stats_rm_result(&n->u, tree_parity(t, parity) > 0 ? 0 : 1, 1);
-			parity = -parity;
+			stats_rm_result(&n->u, loss, u->virtual_loss);
+			loss = 1.0 - loss;
 		}
 	}
 
-- 
2.11.4.GIT