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/*! \internal \file
 * \brief Declares types and functions for comparing trajectories
 * produced by mdrun.
 *
 * \author Mark Abraham <mark.j.abraham@gmail.com>
 * \author Pascal Merz <pascal.merz@me.com>
 * \ingroup module_mdrun_integration_tests
 */
#ifndef GMX_PROGRAMS_MDRUN_TESTS_TRAJECTORYCOMPARISON_H
#define GMX_PROGRAMS_MDRUN_TESTS_TRAJECTORYCOMPARISON_H

#include "testutils/testasserts.h"

#include "comparison_helpers.h"

namespace gmx
{

class TrajectoryFrame;

namespace test
{

class TestReferenceChecker;

/*! \internal
 * \brief Helper struct for testing different trajectory components with different tolerances. */
struct TrajectoryTolerances
{
    /*!@{*/
    /*! \brief Tolerances for reproduction of different quantities. */
    FloatingPointTolerance box, coordinates, velocities, forces;
    /*!@}*/
};

//! Enumeration controlling how data within trajectory frames are compared
enum class ComparisonConditions : int
{
    CompareIfBothFound,
    NoComparison,
    MustCompare,
    CompareIfReferenceFound,
    CompareIfTestFound,
    Count
};

/*! \internal
 * \brief Helper struct to specify the expected behaviour of compareFrames().
 *
 * By default, nothing is required to be compared, but the comparer will
 * compare what it can with the frames it is given.
 *
 * Handling PBC refers to putting all the atoms in the simulation box,
 * which requires that both the PBC type and a simulation box are
 * available from the trajectory frame. */
struct TrajectoryFrameMatchSettings
{
    //! Whether boxes must be compared.
    bool mustCompareBox = false;
    //! Whether PBC will be handled if it can be handled.
    bool handlePbcIfPossible = true;
    //! Whether PBC handling must occur for a valid comparison.
    bool requirePbcHandling = false;
    //! Whether position coordinates must be compared.
    ComparisonConditions coordinatesComparison = ComparisonConditions::CompareIfBothFound;
    //! Whether velocities must be compared.
    ComparisonConditions velocitiesComparison = ComparisonConditions::CompareIfBothFound;
    //! Whether forces must be compared.
    ComparisonConditions forcesComparison = ComparisonConditions::CompareIfBothFound;
    //! How many frames will be compared.
    MaxNumFrames maxNumTrajectoryFrames = MaxNumFrames::compareAllFrames();
};

/*! \internal
 * \brief Function object to compare the fields of two frames vs each others or one
 * frame vs reference data for equality given the \c matchSettings_ and \c tolerances_.
 *
 * If using two frames, they are required to have valid and matching values for
 * time and step. According to \c matchSettings_, box, position coordinates,
 * velocities and/or forces will be compared between frames, using the
 * \c tolerances_. Comparisons will only occur when both frames have
 * the requisite data, and will be expected to be equal within the
 * matching component of \c tolerances_. If a comparison fails, a
 * GoogleTest expectation failure will be given. If a comparison is
 * required by \c matchSettings_ but cannot be done because either (or
 * both) frames lack the requisite data, descriptive expectation
 * failures will be given.
 *
 * When comparing a frame to reference data, according to \c matchSettings_,
 * box, position coordinates, velocities and/or forces will be compared to
 * reference data, using the \c tolerances_. If a comparison fails, a
 * GoogleTest expectation failure will be given. If a comparison is
 * required by \c matchSettings_ but cannot be done because the
 * frame lacks the requisite data, descriptive expectation
 * failures will be given.
 */
class TrajectoryComparison
{
public:
    //! Defaults for trajectory comparisons
    static const TrajectoryTolerances s_defaultTrajectoryTolerances;
    //! Constructor
    TrajectoryComparison(const TrajectoryFrameMatchSettings& matchSettings,
                         const TrajectoryTolerances&         tolerances);
    /*! \brief Compare reference with test given the \c
     * matchSettings_ within \c tolerances_ */
    void operator()(const TrajectoryFrame& reference, const TrajectoryFrame& test) const;
    /*! \brief Compare frame to reference given the \c
     * matchSettings_ within \c tolerances_ */
    void operator()(const TrajectoryFrame& frame, TestReferenceChecker* checker) const;

private:
    //! Specifies expected behavior in comparisons
    TrajectoryFrameMatchSettings matchSettings_;
    //! Trajectory fields to match with given tolerances.
    TrajectoryTolerances tolerances_;
    /*! \brief The number of frames that have been compared until now
     *
     * This field is mutable because the need to update the flag
     * when checking frames is merely an implementation detail,
     * rather than a proper change of internal state triggered
     * by the caller. */
    mutable unsigned int numComparedFrames_ = 0;
};

/*! \internal
 * \brief Helper function comparing a trajectory to reference.
 *
 * This opens a trajectory file, loops over its frames, and uses the
 * \c trajectoryComparison and \c checker arguments to check each frame
 * to reference data.
 *
 * Optionally, the max number of trajectory frames to be compared can
 * be specified to allow to only test the first few frames of a
 * simulation, e.g. to avoid failures due to numerical divergence.
 */
//! \{
void checkTrajectoryAgainstReferenceData(const std::string&          trajectoryFilename,
                                         const TrajectoryComparison& trajectoryComparison,
                                         TestReferenceChecker*       checker);
void checkTrajectoryAgainstReferenceData(const std::string&          trajectoryFilename,
                                         const TrajectoryComparison& trajectoryComparison,
                                         TestReferenceChecker*       checker,
                                         MaxNumFrames                maxNumFrames);
//! \}

} // namespace test
} // namespace gmx

#endif
