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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2026 The Stockfish developers (see AUTHORS file)
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 "timeman.h"
#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdint>
#include "search.h"
#include "ucioption.h"
namespace Stockfish {
TimePoint TimeManagement::optimum() const { return optimumTime; }
TimePoint TimeManagement::maximum() const { return maximumTime; }
void TimeManagement::clear() {
availableNodes = -1; // When in 'nodes as time' mode
}
void TimeManagement::advance_nodes_time(std::int64_t nodes) {
assert(useNodesTime);
availableNodes = std::max(int64_t(0), availableNodes - nodes);
}
// Called at the beginning of the search and calculates
// the bounds of time allowed for the current game ply. We currently support:
// 1) x basetime (+ z increment)
// 2) x moves in y seconds (+ z increment)
void TimeManagement::init(Search::LimitsType& limits,
Color us,
int ply,
const OptionsMap& options,
double& originalTimeAdjust) {
TimePoint npmsec = TimePoint(options["nodestime"]);
// If we have no time, we don't need to fully initialize TM.
// startTime is used by movetime and useNodesTime is used in elapsed calls.
startTime = limits.startTime;
useNodesTime = npmsec != 0;
if (limits.time[us] == 0)
return;
TimePoint moveOverhead = TimePoint(options["Move Overhead"]);
// optScale is a percentage of available time to use for the current move.
// maxScale is a multiplier applied to optimumTime.
double optScale, maxScale;
// 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 (useNodesTime)
{
if (availableNodes == -1) // 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;
moveOverhead *= npmsec;
}
// These numbers are used where multiplications, divisions or comparisons
// with constants are involved.
const int64_t scaleFactor = useNodesTime ? npmsec : 1;
const TimePoint scaledTime = limits.time[us] / scaleFactor;
// Maximum move horizon
int centiMTG = limits.movestogo ? std::min(limits.movestogo * 100, 5000) : 5051;
// If less than one second, gradually reduce mtg
if (scaledTime < 1000)
centiMTG = int(scaledTime * 5.051);
// Make sure timeLeft is > 0 since we may use it as a divisor
TimePoint timeLeft =
std::max(TimePoint(1),
limits.time[us]
+ (limits.inc[us] * (centiMTG - 100) - moveOverhead * (200 + centiMTG)) / 100);
// x basetime (+ z increment)
// If there is a healthy increment, timeLeft can exceed the actual available
// game time for the current move, so also cap to a percentage of available game time.
if (limits.movestogo == 0)
{
// Extra time according to timeLeft
if (originalTimeAdjust < 0)
originalTimeAdjust = 0.3128 * std::log10(timeLeft) - 0.4354;
// Calculate time constants based on current time left.
double logTimeInSec = std::log10(scaledTime / 1000.0);
double optConstant = std::min(0.0032116 + 0.000321123 * logTimeInSec, 0.00508017);
double maxConstant = std::max(3.3977 + 3.03950 * logTimeInSec, 2.94761);
optScale = std::min(0.0121431 + std::pow(ply + 2.94693, 0.461073) * optConstant,
0.213035 * limits.time[us] / timeLeft)
* originalTimeAdjust;
maxScale = std::min(6.67704, maxConstant + ply / 11.9847);
}
// x moves in y seconds (+ z increment)
else
{
optScale =
std::min((0.88 + ply / 116.4) / (centiMTG / 100.0), 0.88 * limits.time[us] / timeLeft);
maxScale = 1.3 + 0.11 * (centiMTG / 100.0);
}
// Limit the maximum possible time for this move
optimumTime = TimePoint(optScale * timeLeft);
maximumTime =
TimePoint(std::min(0.825179 * limits.time[us] - moveOverhead, maxScale * optimumTime)) - 10;
if (options["Ponder"])
optimumTime += optimumTime / 4;
}
} // namespace Stockfish
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