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 // TimeManagement::init() is 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)
37 void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
39 // If we have no time, no need to initialize TM, except for the start time,
40 // which is used by movetime.
41 startTime = limits.startTime;
42 if (limits.time[us] == 0)
45 TimePoint moveOverhead = TimePoint(Options["Move Overhead"]);
46 TimePoint slowMover = TimePoint(Options["Slow Mover"]);
47 TimePoint npmsec = TimePoint(Options["nodestime"]);
49 // optScale is a percentage of available time to use for the current move.
50 // maxScale is a multiplier applied to optimumTime.
51 double optScale, maxScale;
53 // If we have to play in 'nodes as time' mode, then convert from time
54 // to nodes, and use resulting values in time management formulas.
55 // WARNING: to avoid time losses, the given npmsec (nodes per millisecond)
56 // must be much lower than the real engine speed.
59 if (!availableNodes) // Only once at game start
60 availableNodes = npmsec * limits.time[us]; // Time is in msec
62 // Convert from milliseconds to nodes
63 limits.time[us] = TimePoint(availableNodes);
64 limits.inc[us] *= npmsec;
65 limits.npmsec = npmsec;
68 // Maximum move horizon of 50 moves
69 int mtg = limits.movestogo ? std::min(limits.movestogo, 50) : 50;
71 // Make sure timeLeft is > 0 since we may use it as a divisor
72 TimePoint timeLeft = std::max(TimePoint(1),
73 limits.time[us] + limits.inc[us] * (mtg - 1) - moveOverhead * (2 + mtg));
75 // Use extra time with larger increments
76 double optExtra = std::clamp(1.0 + 12.0 * limits.inc[us] / limits.time[us], 1.0, 1.12);
78 // A user may scale time usage by setting UCI option "Slow Mover"
79 // Default is 100 and changing this value will probably lose elo.
80 timeLeft = slowMover * timeLeft / 100;
82 // x basetime (+ z increment)
83 // If there is a healthy increment, timeLeft can exceed actual available
84 // game time for the current move, so also cap to 20% of available game time.
85 if (limits.movestogo == 0)
87 optScale = std::min(0.0120 + std::pow(ply + 3.0, 0.45) * 0.0039,
88 0.2 * limits.time[us] / double(timeLeft))
90 maxScale = std::min(7.0, 4.0 + ply / 12.0);
93 // x moves in y seconds (+ z increment)
96 optScale = std::min((0.88 + ply / 116.4) / mtg,
97 0.88 * limits.time[us] / double(timeLeft));
98 maxScale = std::min(6.3, 1.5 + 0.11 * mtg);
101 // Never use more than 80% of the available time for this move
102 optimumTime = TimePoint(optScale * timeLeft);
103 maximumTime = TimePoint(std::min(0.8 * limits.time[us] - moveOverhead, maxScale * optimumTime)) - 10;
105 if (Options["Ponder"])
106 optimumTime += optimumTime / 4;
109 } // namespace Stockfish