1/*
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
5 Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
6
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
11
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
19*/
20
21#include <algorithm>
22#include <cfloat>
23#include <cmath>
24
25#include "search.h"
26#include "timeman.h"
27#include "uci.h"
28
29TimeManagement Time; // Our global time management object
30
31namespace {
32
33 enum TimeType { OptimumTime, MaxTime };
34
35 constexpr int MoveHorizon = 50; // Plan time management at most this many moves ahead
36 constexpr double MaxRatio = 7.3; // When in trouble, we can step over reserved time with this ratio
37 constexpr double StealRatio = 0.34; // However we must not steal time from remaining moves over this ratio
38
39
40 // move_importance() is a skew-logistic function based on naive statistical
41 // analysis of "how many games are still undecided after n half-moves". Game
42 // is considered "undecided" as long as neither side has >275cp advantage.
43 // Data was extracted from the CCRL game database with some simple filtering criteria.
44
45 double move_importance(int ply) {
46
47 constexpr double XScale = 6.85;
48 constexpr double XShift = 64.5;
49 constexpr double Skew = 0.171;
50
51 return pow((1 + exp((ply - XShift) / XScale)), -Skew) + DBL_MIN; // Ensure non-zero
52 }
53
54 template<TimeType T>
55 TimePoint remaining(TimePoint myTime, int movesToGo, int ply, TimePoint slowMover) {
56
57 constexpr double TMaxRatio = (T == OptimumTime ? 1.0 : MaxRatio);
58 constexpr double TStealRatio = (T == OptimumTime ? 0.0 : StealRatio);
59
60 double moveImportance = (move_importance(ply) * slowMover) / 100.0;
61 double otherMovesImportance = 0.0;
62
63 for (int i = 1; i < movesToGo; ++i)
64 otherMovesImportance += move_importance(ply + 2 * i);
65
66 double ratio1 = (TMaxRatio * moveImportance) / (TMaxRatio * moveImportance + otherMovesImportance);
67 double ratio2 = (moveImportance + TStealRatio * otherMovesImportance) / (moveImportance + otherMovesImportance);
68
69 return TimePoint(myTime * std::min(ratio1, ratio2)); // Intel C++ asks for an explicit cast
70 }
71
72} // namespace
73
74
75/// init() is called at the beginning of the search and calculates the allowed
76/// thinking time out of the time control and current game ply. We support four
77/// different kinds of time controls, passed in 'limits':
78///
79/// inc == 0 && movestogo == 0 means: x basetime [sudden death!]
80/// inc == 0 && movestogo != 0 means: x moves in y minutes
81/// inc > 0 && movestogo == 0 means: x basetime + z increment
82/// inc > 0 && movestogo != 0 means: x moves in y minutes + z increment
83
84void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
85
86 TimePoint minThinkingTime = Options["Minimum Thinking Time"];
87 TimePoint moveOverhead = Options["Move Overhead"];
88 TimePoint slowMover = Options["Slow Mover"];
89 TimePoint npmsec = Options["nodestime"];
90 TimePoint hypMyTime;
91
92 // If we have to play in 'nodes as time' mode, then convert from time
93 // to nodes, and use resulting values in time management formulas.
94 // WARNING: to avoid time losses, the given npmsec (nodes per millisecond)
95 // must be much lower than the real engine speed.
96 if (npmsec)
97 {
98 if (!availableNodes) // Only once at game start
99 availableNodes = npmsec * limits.time[us]; // Time is in msec
100
101 // Convert from milliseconds to nodes
102 limits.time[us] = TimePoint(availableNodes);
103 limits.inc[us] *= npmsec;
104 limits.npmsec = npmsec;
105 }
106
107 startTime = limits.startTime;
108 optimumTime = maximumTime = std::max(limits.time[us], minThinkingTime);
109
110 const int maxMTG = limits.movestogo ? std::min(limits.movestogo, MoveHorizon) : MoveHorizon;
111
112 // We calculate optimum time usage for different hypothetical "moves to go" values
113 // and choose the minimum of calculated search time values. Usually the greatest
114 // hypMTG gives the minimum values.
115 for (int hypMTG = 1; hypMTG <= maxMTG; ++hypMTG)
116 {
117 // Calculate thinking time for hypothetical "moves to go"-value
118 hypMyTime = limits.time[us]
119 + limits.inc[us] * (hypMTG - 1)
120 - moveOverhead * (2 + std::min(hypMTG, 40));
121
122 hypMyTime = std::max(hypMyTime, TimePoint(0));
123
124 TimePoint t1 = minThinkingTime + remaining<OptimumTime>(hypMyTime, hypMTG, ply, slowMover);
125 TimePoint t2 = minThinkingTime + remaining<MaxTime >(hypMyTime, hypMTG, ply, slowMover);
126
127 optimumTime = std::min(t1, optimumTime);
128 maximumTime = std::min(t2, maximumTime);
129 }
130
131 if (Options["Ponder"])
132 optimumTime += optimumTime / 4;
133}
134