2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 enum TimeType { OptimumTime, MaxTime };
32 const int MoveHorizon = 50; // Plan time management at most this many moves ahead
33 const double MaxRatio = 7.0; // When in trouble, we can step over reserved time with this ratio
34 const double StealRatio = 0.33; // However we must not steal time from remaining moves over this ratio
37 // move_importance() is a skew-logistic function based on naive statistical
38 // analysis of "how many games are still undecided after n half-moves". Game
39 // is considered "undecided" as long as neither side has >275cp advantage.
40 // Data was extracted from CCRL game database with some simple filtering criteria.
42 double move_importance(int ply) {
44 const double XScale = 9.3;
45 const double XShift = 59.8;
46 const double Skew = 0.172;
48 return pow((1 + exp((ply - XShift) / XScale)), -Skew) + DBL_MIN; // Ensure non-zero
52 int remaining(int myTime, int movesToGo, int ply, int slowMover)
54 const double TMaxRatio = (T == OptimumTime ? 1 : MaxRatio);
55 const double TStealRatio = (T == OptimumTime ? 0 : StealRatio);
57 double moveImportance = (move_importance(ply) * slowMover) / 100;
58 double otherMovesImportance = 0;
60 for (int i = 1; i < movesToGo; ++i)
61 otherMovesImportance += move_importance(ply + 2 * i);
63 double ratio1 = (TMaxRatio * moveImportance) / (TMaxRatio * moveImportance + otherMovesImportance);
64 double ratio2 = (moveImportance + TStealRatio * otherMovesImportance) / (moveImportance + otherMovesImportance);
66 return int(myTime * std::min(ratio1, ratio2)); // Intel C++ asks an explicit cast
72 /// init() is called at the beginning of the search and calculates the allowed
73 /// thinking time out of the time control and current game ply. We support four
74 /// different kinds of time controls, passed in 'limits':
76 /// inc == 0 && movestogo == 0 means: x basetime [sudden death!]
77 /// inc == 0 && movestogo != 0 means: x moves in y minutes
78 /// inc > 0 && movestogo == 0 means: x basetime + z increment
79 /// inc > 0 && movestogo != 0 means: x moves in y minutes + z increment
81 void TimeManager::init(const Search::LimitsType& limits, Color us, int ply)
83 int minThinkingTime = Options["Minimum Thinking Time"];
84 int moveOverhead = Options["Move Overhead"];
85 int slowMover = Options["Slow Mover"];
87 // Initialize unstablePvFactor to 1 and search times to maximum values
89 optimumSearchTime = maximumSearchTime = std::max(limits.time[us], minThinkingTime);
91 const int MaxMTG = limits.movestogo ? std::min(limits.movestogo, MoveHorizon) : MoveHorizon;
93 // We calculate optimum time usage for different hypothetical "moves to go"-values
94 // and choose the minimum of calculated search time values. Usually the greatest
95 // hypMTG gives the minimum values.
96 for (int hypMTG = 1; hypMTG <= MaxMTG; ++hypMTG)
98 // Calculate thinking time for hypothetical "moves to go"-value
99 int hypMyTime = limits.time[us]
100 + limits.inc[us] * (hypMTG - 1)
101 - moveOverhead * (2 + std::min(hypMTG, 40));
103 hypMyTime = std::max(hypMyTime, 0);
105 int t1 = minThinkingTime + remaining<OptimumTime>(hypMyTime, hypMTG, ply, slowMover);
106 int t2 = minThinkingTime + remaining<MaxTime >(hypMyTime, hypMTG, ply, slowMover);
108 optimumSearchTime = std::min(t1, optimumSearchTime);
109 maximumSearchTime = std::min(t2, maximumSearchTime);
112 if (Options["Ponder"])
113 optimumSearchTime += optimumSearchTime / 4;
115 optimumSearchTime = std::min(optimumSearchTime, maximumSearchTime);