/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm>
#include <cfloat>
#include <cmath>
#include "search.h"
#include "timeman.h"
#include "uci.h"
TimeManagement Time; // Our global time management object
namespace {
enum TimeType { OptimumTime, MaxTime };
constexpr int MoveHorizon = 50; // Plan time management at most this many moves ahead
constexpr double MaxRatio = 7.3; // When in trouble, we can step over reserved time with this ratio
constexpr double StealRatio = 0.34; // However we must not steal time from remaining moves over this ratio
// move_importance() is a skew-logistic function based on naive statistical
// analysis of "how many games are still undecided after n half-moves". Game
// is considered "undecided" as long as neither side has >275cp advantage.
// Data was extracted from the CCRL game database with some simple filtering criteria.
double move_importance(int ply) {
constexpr double XScale = 6.85;
constexpr double XShift = 64.5;
constexpr double Skew = 0.171;
return pow((1 + exp((ply - XShift) / XScale)), -Skew) + DBL_MIN; // Ensure non-zero
}
template<TimeType T>
TimePoint remaining(TimePoint myTime, int movesToGo, int ply, TimePoint slowMover) {
constexpr double TMaxRatio = (T == OptimumTime ? 1.0 : MaxRatio);
constexpr double TStealRatio = (T == OptimumTime ? 0.0 : StealRatio);
double moveImportance = (move_importance(ply) * slowMover) / 100.0;
double otherMovesImportance = 0.0;
for (int i = 1; i < movesToGo; ++i)
otherMovesImportance += move_importance(ply + 2 * i);
double ratio1 = (TMaxRatio * moveImportance) / (TMaxRatio * moveImportance + otherMovesImportance);
double ratio2 = (moveImportance + TStealRatio * otherMovesImportance) / (moveImportance + otherMovesImportance);
return TimePoint(myTime * std::min(ratio1, ratio2)); // Intel C++ asks for an explicit cast
}
} // namespace
/// init() is called at the beginning of the search and calculates the allowed
/// thinking time out of the time control and current game ply. We support four
/// different kinds of time controls, passed in 'limits':
///
/// inc == 0 && movestogo == 0 means: x basetime [sudden death!]
/// inc == 0 && movestogo != 0 means: x moves in y minutes
/// inc > 0 && movestogo == 0 means: x basetime + z increment
/// inc > 0 && movestogo != 0 means: x moves in y minutes + z increment
void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
TimePoint minThinkingTime = Options["Minimum Thinking Time"];
TimePoint moveOverhead = Options["Move Overhead"];
TimePoint slowMover = Options["Slow Mover"];
TimePoint npmsec = Options["nodestime"];
TimePoint hypMyTime;
// If we have to play in 'nodes as time' mode, then convert from time
// to nodes, and use resulting values in time management formulas.
// WARNING: to avoid time losses, the given npmsec (nodes per millisecond)
// must be much lower than the real engine speed.
if (npmsec)
{
if (!availableNodes) // Only once at game start
availableNodes = npmsec * limits.time[us]; // Time is in msec
// Convert from milliseconds to nodes
limits.time[us] = TimePoint(availableNodes);
limits.inc[us] *= npmsec;
limits.npmsec = npmsec;
}
startTime = limits.startTime;
optimumTime = maximumTime = std::max(limits.time[us], minThinkingTime);
const int maxMTG = limits.movestogo ? std::min(limits.movestogo, MoveHorizon) : MoveHorizon;
// We calculate optimum time usage for different hypothetical "moves to go" values
// and choose the minimum of calculated search time values. Usually the greatest
// hypMTG gives the minimum values.
for (int hypMTG = 1; hypMTG <= maxMTG; ++hypMTG)
{
// Calculate thinking time for hypothetical "moves to go"-value
hypMyTime = limits.time[us]
+ limits.inc[us] * (hypMTG - 1)
- moveOverhead * (2 + std::min(hypMTG, 40));
hypMyTime = std::max(hypMyTime, TimePoint(0));
TimePoint t1 = minThinkingTime + remaining<OptimumTime>(hypMyTime, hypMTG, ply, slowMover);
TimePoint t2 = minThinkingTime + remaining<MaxTime >(hypMyTime, hypMTG, ply, slowMover);
optimumTime = std::min(t1, optimumTime);
maximumTime = std::min(t2, maximumTime);
}
if (Options["Ponder"])
optimumTime += optimumTime / 4;
}