2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
29 TimeManagement Time; // Our global time management object
32 // Called at the beginning of the search and calculates
33 // the bounds of time allowed for the current game ply. We currently support:
34 // 1) x basetime (+ z increment)
35 // 2) x moves in y seconds (+ z increment)
36 void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
38 // If we have no time, no need to initialize TM, except for the start time,
39 // which is used by movetime.
40 startTime = limits.startTime;
41 if (limits.time[us] == 0)
44 TimePoint moveOverhead = TimePoint(Options["Move Overhead"]);
45 TimePoint slowMover = TimePoint(Options["Slow Mover"]);
46 TimePoint npmsec = TimePoint(Options["nodestime"]);
48 // optScale is a percentage of available time to use for the current move.
49 // maxScale is a multiplier applied to optimumTime.
50 double optScale, maxScale;
52 // If we have to play in 'nodes as time' mode, then convert from time
53 // to nodes, and use resulting values in time management formulas.
54 // WARNING: to avoid time losses, the given npmsec (nodes per millisecond)
55 // must be much lower than the real engine speed.
58 if (!availableNodes) // Only once at game start
59 availableNodes = npmsec * limits.time[us]; // Time is in msec
61 // Convert from milliseconds to nodes
62 limits.time[us] = TimePoint(availableNodes);
63 limits.inc[us] *= npmsec;
64 limits.npmsec = npmsec;
67 // Maximum move horizon of 50 moves
68 int mtg = limits.movestogo ? std::min(limits.movestogo, 50) : 50;
70 // Make sure timeLeft is > 0 since we may use it as a divisor
71 TimePoint timeLeft = std::max(TimePoint(1), limits.time[us] + limits.inc[us] * (mtg - 1)
72 - moveOverhead * (2 + mtg));
74 // Use extra time with larger increments
75 double optExtra = std::clamp(1.0 + 12.5 * limits.inc[us] / limits.time[us], 1.0, 1.12);
77 // Calculate time constants based on current time left.
78 double optConstant = std::min(0.00335 + 0.0003 * std::log10(limits.time[us] / 1000.0), 0.0048);
79 double maxConstant = std::max(3.6 + 3.0 * std::log10(limits.time[us] / 1000.0), 2.7);
81 // A user may scale time usage by setting UCI option "Slow Mover"
82 // Default is 100 and changing this value will probably lose elo.
83 timeLeft = slowMover * timeLeft / 100;
85 // x basetime (+ z increment)
86 // If there is a healthy increment, timeLeft can exceed actual available
87 // game time for the current move, so also cap to 20% of available game time.
88 if (limits.movestogo == 0)
90 optScale = std::min(0.0120 + std::pow(ply + 3.3, 0.44) * optConstant,
91 0.2 * limits.time[us] / double(timeLeft))
93 maxScale = std::min(6.8, maxConstant + ply / 12.2);
96 // x moves in y seconds (+ z increment)
99 optScale = std::min((0.88 + ply / 116.4) / mtg, 0.88 * limits.time[us] / double(timeLeft));
100 maxScale = std::min(6.3, 1.5 + 0.11 * mtg);
103 // Limit the maximum possible time for this move
104 optimumTime = TimePoint(optScale * timeLeft);
106 TimePoint(std::min(0.84 * limits.time[us] - moveOverhead, maxScale * optimumTime)) - 10;
108 if (Options["Ponder"])
109 optimumTime += optimumTime / 4;
112 } // namespace Stockfish