#ifndef COLVARBIAS_META_H
#define COLVARBIAS_META_H

#include <vector>
#include <list>
#include <sstream>
#include <fstream>

#include "colvarbias.h"
#include "colvargrid.h"

/// Metadynamics bias (implementation of \link colvarbias \endlink)
class colvarbias_meta : public colvarbias {

public:

  /// Communication between different replicas
  enum Communication {
    /// One replica (default)
    single_replica,
    /// Hills added concurrently by several replicas
    multiple_replicas
  };

  /// Communication between different replicas
  Communication comm;

  /// Constructor
  colvarbias_meta (std::string const &conf, char const *key);

  /// Default constructor
  colvarbias_meta();

  /// Destructor
  virtual ~colvarbias_meta();
  
  virtual cvm::real update();

  virtual std::istream & read_restart (std::istream &is);

  virtual std::ostream & write_restart (std::ostream &os);

  virtual void write_pmf();

  class hill;
  typedef std::list<hill>::iterator hill_iter;

protected:

  /// \brief width of a hill
  ///
  /// The local width of each collective variable, multiplied by this
  /// number, provides the hill width along that direction
  cvm::real  hill_width;

  /// \brief Number of simulation steps between two hills
  size_t     new_hill_freq;

  /// Write the hill logfile
  bool           b_hills_traj;
  /// Logfile of hill management (creation and deletion)
  std::ofstream  hills_traj_os;

  /// \brief List of hills used on this bias (total); if a grid is
  /// employed, these don't need to be updated at every time step
  std::list<hill> hills;

  /// \brief Iterator to the first of the "newest" hills (when using
  /// grids, those who haven't been mapped yet)
  hill_iter new_hills_begin;

  /// \brief List of hills used on this bias that are on the boundary
  /// edges; these are updated regardless of whether hills are used
  std::list<hill> hills_off_grid;

  /// \brief Same as new_hills_begin, but for the off-grid ones
  hill_iter new_hills_off_grid_begin;

  /// Regenerate the hills_off_grid list
  void recount_hills_off_grid (hill_iter h_first, hill_iter h_last,
                               colvar_grid_scalar *ge);

  /// Read a hill from a file
  std::istream & read_hill (std::istream &is);

  /// \brief step present in a state file
  /// 
  /// When using grids and reading state files containing them
  /// (multiple replicas), this is used to check whether a hill is
  /// newer or older than the grids
  size_t                   state_file_step;

  /// \brief Add a new hill; if a .hills trajectory is written,
  /// write it there; if there is more than one replica, communicate
  /// it to the others
  virtual std::list<hill>::const_iterator create_hill (hill const &h);

  /// \brief Remove a previously saved hill (returns an iterator for
  /// the next hill in the list)
  virtual std::list<hill>::const_iterator delete_hill (hill_iter &h);

  /// \brief Calculate the values of the hills, incrementing
  /// bias_energy
  virtual void calc_hills (hill_iter  h_first,
                           hill_iter  h_last,
                           cvm::real &energy,
                           std::vector<colvarvalue> const &values = std::vector<colvarvalue> (0));

  /// \brief Calculate the forces acting on the i-th colvar,
  /// incrementing colvar_forces[i]; must be called after calc_hills
  /// each time the values of the colvars are changed
  virtual void calc_hills_force (size_t const &i,
                                 hill_iter h_first,
                                 hill_iter h_last,
                                 std::vector<colvarvalue> &forces,
                                 std::vector<colvarvalue> const &values = std::vector<colvarvalue> (0));


  /// Height of new hills
  cvm::real  hill_weight;

  /// \brief Bin the hills on grids of energy and forces, and use them
  /// to force the colvars (as opposed to deriving the hills analytically)
  bool       use_grids;

  /// \brief Rebin the hills upon restarting
  bool       rebin_grids;

  /// \brief Should the grids be expanded if necessary?
  bool       expand_grids;

  /// \brief How often the hills should be projected onto the grids
  size_t     grids_freq;

  /// \brief Whether to keep the hills in the restart file (e.g. to do
  /// meaningful accurate rebinning afterwards)
  bool       keep_hills;

  /// \brief Dump the free energy surface (.pmf file) every restartFrequency
  bool       dump_fes;

  /// \brief Dump the free energy surface (.pmf file) every restartFrequency
  /// using only the hills from this replica (only applicable to more than one replica)
  bool       dump_replica_fes;

  /// \brief Dump the free energy surface files at different
  /// time steps, appending the step number to each file
  bool       dump_fes_save;

  /// \brief Try to read the restart information by allocating new
  /// grids before replacing the current ones (used e.g. in
  /// multiple_replicas)
  bool       safely_read_restart;

  /// Hill energy, cached on a grid
  colvar_grid_scalar    *hills_energy;

  /// Hill forces, cached on a grid
  colvar_grid_gradient  *hills_energy_gradients;

  /// \brief Project the selected hills onto grids
  void project_hills (hill_iter h_first, hill_iter h_last,
                      colvar_grid_scalar *ge, colvar_grid_gradient *gf);


  // Multiple Replicas variables and functions

  /// \brief Identifier for this replica
  std::string            replica_id;

  /// \brief File containing the paths to the output files from this replica
  std::string            replica_file_name;

  /// \brief Read the existing replicas on registry
  virtual void update_replicas_registry();

  /// \brief Read new data from replicas' files
  virtual void read_replica_files();

  /// \brief Write data to other replicas
  virtual void write_replica_state_file();

  /// \brief Additional, "mirror" metadynamics biases, to collect info
  /// from the other replicas
  ///
  /// These are supposed to be synchronized by reading data from the
  /// other replicas, and not be modified by the "local" replica
  std::vector<colvarbias_meta *> replicas;

  /// \brief Frequency at which data the "mirror" biases are updated
  size_t                 replica_update_freq;

  /// List of replicas (and their output list files): contents are
  /// copied into replicas_registry for convenience
  std::string            replicas_registry_file;
  /// List of replicas (and their output list files)
  std::string            replicas_registry;
  /// List of files written by this replica
  std::string            replica_list_file;

  /// Hills energy and gradients written specifically for other
  /// replica (in addition to its own restart file)
  std::string            replica_state_file;
  /// Whether a mirror bias has read the latest version of its state file
  bool                   replica_state_file_in_sync;

  /// If there was a failure reading one of the files (because they
  /// are not complete), this counter is incremented
  size_t                 update_status;

  /// Explicit hills communicated between replicas
  ///
  /// This file becomes empty after replica_state_file is rewritten
  std::string            replica_hills_file;

  /// \brief Output stream corresponding to replica_hills_file
  std::ofstream          replica_hills_os;

  /// Position within replica_hills_file (when reading it)
  size_t                 replica_hills_file_pos;

};




/// \brief A hill for the metadynamics bias
class colvarbias_meta::hill {

protected:

  /// Value of the hill function (ranges between 0 and 1)
  cvm::real hill_value;

  /// Scale factor, which could be modified at runtime (default: 1)
  cvm::real sW;

  /// Maximum height in energy of the hill
  cvm::real W;

  /// Center of the hill in the collective variable space
  std::vector<colvarvalue>  centers;

  /// Widths of the hill in the collective variable space
  std::vector<cvm::real>    widths;

public:

  friend class colvarbias_meta;

  /// Time step at which this hill was added
  size_t      it;

  /// Identity of the replica who added this hill (only in multiple replica simulations)
  std::string replica;

  /// \brief Runtime constructor: data are read directly from
  /// collective variables \param weight Weight of the hill \param
  /// cv Pointer to the array of collective variables involved \param
  /// replica (optional) Identity of the replica which creates the
  /// hill
  inline hill (cvm::real             const &W_in,
               std::vector<colvar *>       &cv,
               cvm::real             const &hill_width,
               std::string           const &replica_in = "")
    : sW (1.0),
      W (W_in),
      centers (cv.size()),
      widths (cv.size()),
      it (cvm::it),
      replica (replica_in)
  {
    for (size_t i = 0; i < cv.size(); i++) {
      centers[i].type (cv[i]->type());
      centers[i] = cv[i]->value();
      widths[i] = cv[i]->width * hill_width;
    }
    if (cvm::debug()) 
      cvm::log ("New hill, applied to "+cvm::to_str (cv.size())+
                " collective variables, with centers "+
                cvm::to_str (centers)+", widths "+
                cvm::to_str (widths)+" and weight "+
                cvm::to_str (W)+".\n");
  }

  /// \brief General constructor: all data are explicitly passed as
  /// arguments (used for instance when reading hills saved on a
  /// file) \param it Time step of creation of the hill \param
  /// weight Weight of the hill \param centers Center of the hill
  /// \param widths Width of the hill around centers \param replica
  /// (optional) Identity of the replica which creates the hill
  inline hill (size_t                    const &it_in,
               cvm::real                 const &W_in,
               std::vector<colvarvalue>  const &centers_in,
               std::vector<cvm::real>    const &widths_in,
               std::string               const &replica_in = "")
    : sW (1.0),
      W (W_in),
      centers (centers_in),
      widths (widths_in),
      it (it_in),
      replica (replica_in)
  {}

  /// Copy constructor
  inline hill (colvarbias_meta::hill const &h)
    : sW (1.0),
      W (h.W),
      centers (h.centers),
      widths (h.widths),
      it (h.it),
      replica (h.replica)
  {}

  /// Destructor
  inline ~hill()
  {}
  
  /// Get the energy
  inline cvm::real energy()
  {
    return W * sW * hill_value;
  }

  /// Get the energy using another hill weight
  inline cvm::real energy (cvm::real const &new_weight)
  {
    return new_weight * sW * hill_value;
  }

  /// Get the current hill value
  inline cvm::real const &value()
  {
    return hill_value;
  }

  /// Set the hill value as specified
  inline void value (cvm::real const &new_value)
  {
    hill_value = new_value;
  }

  /// Get the weight
  inline cvm::real weight()
  {
    return W * sW;
  }

  /// Scale the weight with this factor (by default 1.0 is used)
  inline void scale (cvm::real const &new_scale_fac)
  {
    sW = new_scale_fac;
  }

  /// Get the center of the hill
  inline std::vector<colvarvalue> & center()
  {
    return centers;
  }

  /// Get the i-th component of the center
  inline colvarvalue & center (size_t const &i)
  {
    return centers[i];
  }

  /// Comparison operator
  inline friend bool operator < (hill const &h1, hill const &h2)
  {
    if (h1.it < h2.it) return true;
    else return false;
  }

  /// Comparison operator
  inline friend bool operator <= (hill const &h1, hill const &h2)
  {
    if (h1.it <= h2.it) return true;
    else return false;
  }

  /// Comparison operator
  inline friend bool operator > (hill const &h1, hill const &h2)
  {
    if (h1.it > h2.it) return true;
    else return false;
  }

  /// Comparison operator
  inline friend bool operator >= (hill const &h1, hill const &h2)
  {
    if (h1.it >= h2.it) return true;
    else return false;
  }

  /// Comparison operator
  inline friend bool operator == (hill const &h1, hill const &h2)
  {
    if ( (h1.it >= h2.it) && (h1.replica == h2.replica) ) return true;
    else return false;
  }

  /// Represent the hill ina string suitable for a trajectory file
  std::string output_traj();

  /// Write the hill to an output stream
  inline friend std::ostream & operator << (std::ostream &os,
                                            hill const &h);

};


#endif


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