2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 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/>.
28 TimeManagement Time; // Our global time management object
32 enum TimeType { OptimumTime, MaxTime };
34 const int MoveHorizon = 50; // Plan time management at most this many moves ahead
35 const double MaxRatio = 6.93; // When in trouble, we can step over reserved time with this ratio
36 const double StealRatio = 0.36; // However we must not steal time from remaining moves over this ratio
39 // move_importance() is a skew-logistic function based on naive statistical
40 // analysis of "how many games are still undecided after n half-moves". Game
41 // is considered "undecided" as long as neither side has >275cp advantage.
42 // Data was extracted from CCRL game database with some simple filtering criteria.
44 double move_importance(int ply) {
46 const double XScale = 8.27;
47 const double XShift = 59.;
48 const double Skew = 0.179;
50 return pow((1 + exp((ply - XShift) / XScale)), -Skew) + DBL_MIN; // Ensure non-zero
54 int remaining(int myTime, int movesToGo, int ply, int slowMover)
56 const double TMaxRatio = (T == OptimumTime ? 1 : MaxRatio);
57 const double TStealRatio = (T == OptimumTime ? 0 : StealRatio);
59 double moveImportance = (move_importance(ply) * slowMover) / 100;
60 double otherMovesImportance = 0;
62 for (int i = 1; i < movesToGo; ++i)
63 otherMovesImportance += move_importance(ply + 2 * i);
65 double ratio1 = (TMaxRatio * moveImportance) / (TMaxRatio * moveImportance + otherMovesImportance);
66 double ratio2 = (moveImportance + TStealRatio * otherMovesImportance) / (moveImportance + otherMovesImportance);
68 return int(myTime * std::min(ratio1, ratio2)); // Intel C++ asks an explicit cast
74 /// init() is called at the beginning of the search and calculates the allowed
75 /// thinking time out of the time control and current game ply. We support four
76 /// different kinds of time controls, passed in 'limits':
78 /// inc == 0 && movestogo == 0 means: x basetime [sudden death!]
79 /// inc == 0 && movestogo != 0 means: x moves in y minutes
80 /// inc > 0 && movestogo == 0 means: x basetime + z increment
81 /// inc > 0 && movestogo != 0 means: x moves in y minutes + z increment
83 void TimeManagement::init(Search::LimitsType& limits, Color us, int ply)
85 int minThinkingTime = Options["Minimum Thinking Time"];
86 int moveOverhead = Options["Move Overhead"];
87 int slowMover = Options["Slow Mover"];
88 int npmsec = Options["nodestime"];
90 // If we have to play in 'nodes as time' mode, then convert from time
91 // to nodes, and use resulting values in time management formulas.
92 // WARNING: Given npms (nodes per millisecond) must be much lower then
93 // real engine speed to avoid time losses.
96 if (!availableNodes) // Only once at game start
97 availableNodes = npmsec * limits.time[us]; // Time is in msec
99 // Convert from millisecs to nodes
100 limits.time[us] = (int)availableNodes;
101 limits.inc[us] *= npmsec;
102 limits.npmsec = npmsec;
105 startTime = limits.startTime;
106 unstablePvFactor = 1;
107 optimumTime = maximumTime = std::max(limits.time[us], minThinkingTime);
109 const int MaxMTG = limits.movestogo ? std::min(limits.movestogo, MoveHorizon) : MoveHorizon;
111 // We calculate optimum time usage for different hypothetical "moves to go"-values
112 // and choose the minimum of calculated search time values. Usually the greatest
113 // hypMTG gives the minimum values.
114 for (int hypMTG = 1; hypMTG <= MaxMTG; ++hypMTG)
116 // Calculate thinking time for hypothetical "moves to go"-value
117 int hypMyTime = limits.time[us]
118 + limits.inc[us] * (hypMTG - 1)
119 - moveOverhead * (2 + std::min(hypMTG, 40));
121 hypMyTime = std::max(hypMyTime, 0);
123 int t1 = minThinkingTime + remaining<OptimumTime>(hypMyTime, hypMTG, ply, slowMover);
124 int t2 = minThinkingTime + remaining<MaxTime >(hypMyTime, hypMTG, ply, slowMover);
126 optimumTime = std::min(t1, optimumTime);
127 maximumTime = std::min(t2, maximumTime);
130 if (Options["Ponder"])
131 optimumTime += optimumTime / 4;