Domain decomposition and PME load balancing for modular simulator

[gromacs.git] / src / gromacs / modularsimulator / statepropagatordata.h

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/*! \libinternal
 * \brief Declares the state for the modular simulator
 *
 * \author Pascal Merz <pascal.merz@me.com>
 * \ingroup module_modularsimulator
 */

#ifndef GMX_MODULARSIMULATOR_STATEPROPAGATORDATA_H
#define GMX_MODULARSIMULATOR_STATEPROPAGATORDATA_H

#include "gromacs/gpu_utils/hostallocator.h"
#include "gromacs/math/paddedvector.h"
#include "gromacs/math/vectypes.h"

#include "modularsimulatorinterfaces.h"

struct gmx_mdoutf;
struct t_commrec;
struct t_inputrec;
class t_state;
struct t_mdatoms;

namespace gmx
{
enum class ConstraintVariable;

//! \addtogroup module_modularsimulator
//! \{

/*! \libinternal
 * \brief StatePropagatorData and associated data
 *
 * The `StatePropagatorData` contains a little more than the pure
 * statistical-physical micro state, namely the positions,
 * velocities, forces, and box matrix, as well as a backup of
 * the positions and box of the last time step. While it takes
 * part in the simulator loop to be able to backup positions /
 * boxes and save the current state if needed, it's main purpose
 * is to offer access to its data via getter methods. All elements
 * reading or writing to this data need a pointer to the
 * `StatePropagatorData` and need to request their data explicitly. This
 * will later simplify the understanding of data dependencies
 * between elements.
 *
 * The `StatePropagatorData` takes part in the simulator run, as it might
 * have to save a valid state at the right moment during the
 * integration. Placing the StatePropagatorData correctly is for now the
 * duty of the simulator builder - this might be automatized later
 * if we have enough meta-data of the variables (i.e., if
 * `StatePropagatorData` knows at which time the variables currently are,
 * and can decide when a valid state (full-time step of all
 * variables) is reached. The `StatePropagatorData` is also a client of
 * both the trajectory signaller and writer - it will save a
 * state for later writeout during the simulator step if it
 * knows that trajectory writing will occur later in the step,
 * and it knows how to write to file given a file pointer by
 * the `TrajectoryElement`.
 *
 * Note that the `StatePropagatorData` can be converted to and from the
 * legacy `t_state` object. This is useful when dealing with
 * functionality which has not yet been adapted to use the new
 * data approach - of the elements currently implemented, only
 * domain decomposition, PME load balancing, and the initial
 * constraining are using this.
 */
class StatePropagatorData final :
    public                ISimulatorElement,
    public                ITrajectoryWriterClient,
    public                ITrajectorySignallerClient
{
    public:
        //! Constructor
        StatePropagatorData(
            int               numAtoms,
            FILE             *fplog,
            const t_commrec  *cr,
            t_state          *globalState,
            int               nstxout,
            int               nstvout,
            int               nstfout,
            int               nstxout_compressed,
            bool              useGPU,
            const t_inputrec *inputrec,
            const t_mdatoms  *mdatoms);

        // Allow access to state
        //! Get write access to position vector
        ArrayRefWithPadding<RVec> positionsView();
        //! Get read access to position vector
        ArrayRefWithPadding<const RVec> constPositionsView() const;
        //! Get write access to previous position vector
        ArrayRefWithPadding<RVec> previousPositionsView();
        //! Get read access to previous position vector
        ArrayRefWithPadding<const RVec> constPreviousPositionsView() const;
        //! Get write access to velocity vector
        ArrayRefWithPadding<RVec> velocitiesView();
        //! Get read access to velocity vector
        ArrayRefWithPadding<const RVec> constVelocitiesView() const;
        //! Get write access to force vector
        ArrayRefWithPadding<RVec> forcesView();
        //! Get read access to force vector
        ArrayRefWithPadding<const RVec> constForcesView() const;
        //! Get pointer to box
        rvec *box();
        //! Get pointer to previous box
        rvec *previousBox();
        //! Get the local number of atoms
        int localNumAtoms();

        /*! \brief Register run function for step / time
         *
         * This needs to be called during the integration part of the simulator,
         * at the moment at which the state is at a full time step. Positioning
         * this element is the responsibility of the programmer writing the
         * integration algorithm! If the current step is a trajectory writing
         * step, StatePropagatorData will save a backup for later writeout.
         *
         * This is also the place at which the current state becomes the previous
         * state.
         *
         * @param step                 The step number
         * @param time                 The time
         * @param registerRunFunction  Function allowing to register a run function
         */
        void scheduleTask(
            Step step, Time time,
            const RegisterRunFunctionPtr &registerRunFunction) override;

        /*! \brief Backup starting velocities
         *
         * This is only needed for vv, where the first (velocity) half step is only
         * used to compute the constraint virial, but the velocities need to be reset
         * after.
         * TODO: There must be a more elegant solution to this!
         */
        void elementSetup() override;

        //! No element teardown needed
        void elementTeardown() override {}

        //! @cond
        // (doxygen doesn't like these)
        // Classes which need access to legacy state
        friend class DomDecHelper;
        friend class PmeLoadBalanceHelper;
        //! @endcond

    private:
        //! The total number of atoms in the system
        int totalNumAtoms_;
        //! The position writeout frequency
        int nstxout_;
        //! The velocity writeout frequency
        int nstvout_;
        //! The force writeout frequency
        int nstfout_;
        //! The compressed position writeout frequency
        int nstxout_compressed_;

        //! The local number of atoms
        int                    localNAtoms_;
        //! The position vector
        PaddedHostVector<RVec> x_;
        //! The position vector of the previous step
        PaddedVector<RVec>     previousX_;
        //! The velocity vector
        PaddedVector<RVec>     v_;
        //! The force vector
        PaddedVector<RVec>     f_;
        //! The box matrix
        matrix                 box_;
        //! The box matrix of the previous step
        matrix                 previousBox_;
        //! Bit-flags for legacy t_state compatibility
        unsigned int           flags_;
        //! The DD partitioning count for legacy t_state compatibility
        int                    ddpCount_;

        //! Move x_ to previousX_
        void copyPosition();
        //! OMP helper to move x_ to previousX_
        void copyPosition(int start, int end);

        // Access to legacy state
        //! Get a deep copy of the current state in legacy format
        std::unique_ptr<t_state> localState();
        //! Update the current state with a state in legacy format
        void setLocalState(std::unique_ptr<t_state> state);
        //! Get a pointer to the global state
        t_state *globalState();
        //! Get a force pointer
        PaddedVector<gmx::RVec> *forcePointer();

        //! Pointer to keep a backup of the state for later writeout
        std::unique_ptr<t_state> localStateBackup_;
        //! Step at which next writeout occurs
        Step                     writeOutStep_;
        //! Backup current state
        void saveState();

        //! ITrajectorySignallerClient implementation
        SignallerCallbackPtr
        registerTrajectorySignallerCallback(TrajectoryEvent event) override;

        //! ITrajectoryWriterClient implementation
        ITrajectoryWriterCallbackPtr
        registerTrajectoryWriterCallback(TrajectoryEvent event) override;

        //! Callback writing the state to file
        void write(gmx_mdoutf *outf, Step step, Time time);

        //! Whether we're doing VV and need to reset velocities after the first half step
        bool               vvResetVelocities_;
        //! Velocities backup for VV
        PaddedVector<RVec> velocityBackup_;
        //! Function resetting the velocities
        void resetVelocities();

        // Access to ISimulator data
        //! Handles logging.
        FILE            *fplog_;
        //! Handles communication.
        const t_commrec *cr_;
        //! Full simulation state (only non-nullptr on master rank).
        t_state         *globalState_;

        //! No trajectory writer setup needed
        void trajectoryWriterSetup(gmx_mdoutf gmx_unused *outf) override {}
        //! No trajectory writer teardown needed
        void trajectoryWriterTeardown(gmx_mdoutf gmx_unused *outf) override {}
};

//! /}
}      // namespace gmx

#endif // GMX_MODULARSIMULATOR_STATEPROPAGATORDATA_H