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#ifndef _repl_ex_h
#define _repl_ex_h

#include <cstdio>

#include "gromacs/utility/basedefinitions.h"
#include "gromacs/utility/real.h"

struct gmx_enerdata_t;
struct gmx_multisim_t;
struct t_commrec;
struct t_inputrec;
class t_state;

/* The parameters for the replica exchange algorithm */
struct ReplicaExchangeParameters
{
    ReplicaExchangeParameters() :
        exchangeInterval(0),
        numExchanges(0),
        randomSeed(-1)
    {
    };

    int exchangeInterval; /* Interval in steps at which to attempt exchanges, 0 means no replica exchange */
    int numExchanges;     /* The number of exchanges to attempt at an exchange step */
    int randomSeed;       /* The random seed, -1 means generate a seed */
};

/* Abstract type for replica exchange */
typedef struct gmx_repl_ex *gmx_repl_ex_t;

gmx_repl_ex_t
init_replica_exchange(FILE                            *fplog,
                      const gmx_multisim_t            *ms,
                      int                              numAtomsInSystem,
                      const t_inputrec                *ir,
                      const ReplicaExchangeParameters &replExParams);
/* Should only be called on the master ranks */

gmx_bool replica_exchange(FILE *fplog,
                          const t_commrec *cr,
                          gmx_repl_ex_t re,
                          t_state *state, const gmx_enerdata_t *enerd,
                          t_state *state_local,
                          gmx_int64_t step, real time);
/* Attempts replica exchange, should be called on all ranks.
 * Returns TRUE if this state has been exchanged.
 * When running each replica in parallel,
 * this routine collects the state on the master rank before exchange.
 * With domain decomposition, the global state after exchange is stored
 * in state and still needs to be redistributed over the ranks.
 */

void print_replica_exchange_statistics(FILE *fplog, gmx_repl_ex_t re);
/* Should only be called on the master ranks */

#endif  /* _repl_ex_h */