From 6f465d10588d756aef6a09474b329df7088197ea Mon Sep 17 00:00:00 2001
From: Jean-loup Gailly <jloup@gailly.net>
Date: Mon, 1 Feb 2010 19:13:42 +0100
Subject: [PATCH] Do not use all memory during pondering.

---
 uct/internal.h | 3 ++-
 uct/uct.c      | 6 ++++--
 uct/walk.c     | 9 ++++++++-
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/uct/internal.h b/uct/internal.h
index 0e9912e..74d9979 100644
--- a/uct/internal.h
+++ b/uct/internal.h
@@ -41,7 +41,8 @@ struct uct {
 	} thread_model;
 	bool parallel_tree;
 	bool virtual_loss;
-	bool pondering;
+	bool pondering_opt; /* User wants pondering */
+	bool pondering; /* Actually pondering now */
 	int fuseki_end;
 	int yose_start;
 
diff --git a/uct/uct.c b/uct/uct.c
index ec2e26f..278a976 100644
--- a/uct/uct.c
+++ b/uct/uct.c
@@ -610,6 +610,7 @@ uct_pondering_start(struct uct *u, struct board *b0, struct tree *t, enum stone
 {
 	if (UDEBUGL(1))
 		fprintf(stderr, "Starting to ponder with color %s\n", stone2str(stone_other(color)));
+	u->pondering = true;
 
 	/* We need a local board copy to ponder upon. */
 	struct board *b = malloc(sizeof(*b)); board_copy(b, b0);
@@ -627,6 +628,7 @@ uct_pondering_start(struct uct *u, struct board *b0, struct tree *t, enum stone
 static void
 uct_pondering_stop(struct uct *u)
 {
+	u->pondering = false;
 	if (!thread_manager_running)
 		return;
 
@@ -702,7 +704,7 @@ uct_genmove(struct engine *e, struct board *b, struct time_info *ti, enum stone
 	 * Of course this is the case for opponent resign as well.
 	 * (ii) More importantly, the ownermap will get skewed since
 	 * the UCT will start cutting off any playouts. */
-	if (u->pondering && !is_pass(best->coord)) {
+	if (u->pondering_opt && !is_pass(best->coord)) {
 		uct_pondering_start(u, b, u->t, stone_other(color));
 	}
 	if (UDEBUGL(2)) {
@@ -885,7 +887,7 @@ uct_state_init(char *arg, struct board *b)
 				}
 			} else if (!strcasecmp(optname, "pondering")) {
 				/* Keep searching even during opponent's turn. */
-				u->pondering = !optval || atoi(optval);
+				u->pondering_opt = !optval || atoi(optval);
 			} else if (!strcasecmp(optname, "fuseki_end") && optval) {
 				/* At the very beginning it's not worth thinking too long because the
 				 * playout evaluations are very noisy. So gradually increase the thinking
diff --git a/uct/walk.c b/uct/walk.c
index 4972ea9..ad2fb56 100644
--- a/uct/walk.c
+++ b/uct/walk.c
@@ -19,6 +19,9 @@
 #include "uct/uct.h"
 #include "uct/walk.h"
 
+/*Fill at most 90% of the tree when pondering: */
+#define PONDERING_MAX_MEM_PERCENT 90
+
 float
 uct_get_extra_komi(struct uct *u, struct board *b)
 {
@@ -91,6 +94,10 @@ uct_leaf_node(struct uct *u, struct board *b, enum stone player_color,
 	enum stone next_color = stone_other(node_color);
 	int parity = (next_color == player_color ? 1 : -1);
 
+	unsigned long max_tree_size = u->max_tree_size;
+	if (u->pondering)
+		max_tree_size = (max_tree_size * PONDERING_MAX_MEM_PERCENT) / 100;
+
 	/* We need to make sure only one thread expands the node. If
 	 * we are unlucky enough for two threads to meet in the same
 	 * node, the latter one will simply do another simulation from
@@ -98,7 +105,7 @@ uct_leaf_node(struct uct *u, struct board *b, enum stone player_color,
 	 * the maximum in multi-threaded case but not by much so it's ok.
 	 * The size test must be before the test&set not after, to allow
 	 * expansion of the node later if enough nodes have been freed. */
-	if (n->u.playouts >= u->expand_p && t->nodes_size < u->max_tree_size
+	if (n->u.playouts >= u->expand_p && t->nodes_size < max_tree_size
 	    && !__sync_lock_test_and_set(&n->is_expanded, 1)) {
 		tree_expand_node(t, n, b, next_color, u, parity);
         }
-- 
2.11.4.GIT