+/*
+ * This file is part of the GROMACS molecular simulation package.
+ *
+ * Copyright (c) 2020, by the GROMACS development team, led by
+ * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
+ * and including many others, as listed in the AUTHORS file in the
+ * top-level source directory and at http://www.gromacs.org.
+ *
+ * GROMACS is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1
+ * of the License, or (at your option) any later version.
+ *
+ * GROMACS 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
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+ */
+/*! \internal \file
+ * \brief Declares and defines the EnergyDriftTracker class.
+ *
+ * \author Berk Hess <hess@kth.se>
+ *
+ * \ingroup module_mdlib
+ */
+#ifndef GMX_MDLIB_ENERGYDRIFTTRACKER_H
+#define GMX_MDLIB_ENERGYDRIFTTRACKER_H
+
+#include <string>
+
+#include "gromacs/utility/real.h"
+
+namespace gmx
+{
+
+/*! \internal
+ * \brief Class for tracking and printing the drift in the conserved energy quantity
+ */
+class EnergyDriftTracker
+{
+public:
+ /*! \brief Constructor
+ *
+ * \param[in] numAtoms The total number of atoms in the system
+ */
+ EnergyDriftTracker(int numAtoms) : numAtoms_(numAtoms) {}
+
+ //! Add a point to the conserved energy tracking
+ void addPoint(double time, double energy);
+
+ //! Returns the time of the last point minus the time of the first point
+ double timeInterval() const { return lastTime_ - firstTime_; }
+
+ //! Returns the energy drift over the measured interval
+ double energyDrift() const;
+
+ /*! \brief Returns two-line string with the time interval and drift over the interval
+ *
+ * \param[in] partName A descriptive name for the period over which the tracking occured
+ */
+ std::string energyDriftString(const std::string& partName) const;
+
+private:
+ //! Whether we stored the first point
+ bool storedFirst_ = false;
+ //! The first time stored
+ double firstTime_ = 0;
+ //! The energy for the first time point
+ double firstEnergy_ = 0;
+ //! The last time stored
+ double lastTime_ = 0;
+ //! The energy for the last time point
+ double lastEnergy_ = 0;
+ //! The number of atoms in the system
+ int numAtoms_;
+};
+
+} // namespace gmx
+
+#endif