memoize

uttt.c

@@ -916,10 +916,55 @@ struct ut_move ut_minimax(int (*value)(const struct ut_state *state), const stru
 	return best_move;
 }
 
+struct ut_statevalue
+{
+	unsigned char tilesxo[21];
+	char value;
+};
+struct ut_statevalue ut_rolloutCache[16777216];
+void ut_statetokey(struct ut_statevalue *sv, const struct ut_state *state)
+{
+	memset(sv->tilesxo, 0, sizeof(sv->tilesxo));
+	char *tiles = (char *)state->tiles;
+	for(int i = 0; i < sizeof(state->tiles); i++)
+		sv->tilesxo[i / 4] |= ((tiles[i] == 'X') * (1 << ((i % 4) * 2))) |
+			              ((tiles[i] == 'O') * (1 << ((i % 4) * 2 + 1)));
+}
+unsigned long ut_keytoidx(struct ut_statevalue *sv)
+{
+	//djb2 hash
+	unsigned long hash = 5831;
+	for(int i = 0; i < sizeof(sv->tilesxo); i++)
+	{
+		hash = ((hash << 5) + hash) ^ sv->tilesxo[i];
+	}
+	return hash % (sizeof(ut_rolloutCache) / sizeof(ut_rolloutCache[0]));
+}
+int ut_memValue(int value, const struct ut_state *state)
+{
+	struct ut_statevalue sv;
+	sv.value = value;
+	ut_statetokey(&sv, state);
+	ut_rolloutCache[ut_keytoidx(&sv)] = sv;
+	return value;
+}
+int ut_getValue(const struct ut_state *state, int *value)
+{
+	struct ut_statevalue sv;
+	ut_statetokey(&sv, state);
+	struct ut_statevalue *entry = &ut_rolloutCache[ut_keytoidx(&sv)];
+	if(memcmp(sv.tilesxo, entry->tilesxo, sizeof(sv.tilesxo))) {return 1;}
+	*value = entry->value;
+	return 0;
+}
+
 #define UT_RDEPTH 2
-#define UT_RTURNS 2
+#define UT_RTURNS 9
 int ut_rollout(const struct ut_state *state)
 {
+	// memoization
+	int value;
+	if(!ut_getValue(state, &value)) {return value;}
 
 	struct ut_state rstate = *state;
 	int moves = 0;
@@ -933,12 +978,12 @@ int ut_rollout(const struct ut_state *state)
 		}
 		moves++;
 	}
-	return  (winner == 'X') ? (UT_VALUEMAX - moves) :
-		(winner == 'O') ? (UT_VALUEMIN + moves) :
-		(winner == ' ') ? 0 : ut_value(&rstate);
+	return ut_memValue((winner == 'X') ? (UT_VALUEMAX - moves) :
+		           (winner == 'O') ? (UT_VALUEMIN + moves) :
+		           (winner == ' ') ? 0 : ut_value(&rstate), state);
 }
 
-#define UT_DEPTH 5
+#define UT_DEPTH 4
 int ut_agentgetmove(const struct ut_state *state, const struct ut_game *game, struct ut_move *move)
 {
 	*move = ut_minimax(ut_rollout, state, UT_DEPTH);