Implement MPI send/receive functions for ClusterOutputInfo

#ifndef INCLUDE_OUTPUTS_H_

#define INCLUDE_OUTPUTS_H_

//! \brief General output type identifier.

#define OUT_GNRL 0

//! \brief Cluster output type identifier.

#define OUT_CLST 1

//! \brief Inclusion output type identifier.

#define OUT_INCL 2

//! \brief Single sphere output type identifier.

#define OUT_SPHR 3

/*! \brief Class to collect output information for scattering from clusters.

 *

 * The results of the calculation can be saved in different formats.

   * \return result: `int` Exit code (0 if successful).

   */

  int write(const std::string &output, const std::string &format);

#ifdef MPI_VERSION

  /*! \brief Receive output data from worker processes.

   *

   * This function is invoked by the MPI rank-0 process to fetch the

   * output data produced by higher rank processes. When calling this

   * function, process 0 halts until a valid data chunk is transmitted

   * by the queried process.

   *

   * \param mpidata: `const mixMPI*` Pointer to a `mixMPI` instance.

   * \param pid: `int` Rank of the process that is transmitting data.

   * \return result: `int` An exit code (0 for success).

   */

  int mpireceive(const mixMPI* mpidata, int pid);

  /*! \brief Send output data to process 0.

   *

   * This function is invoked by non-zero ranked MPI processes when

   * they are ready to send back the output data. When a process meets

   * this function call, it halts until MPI process 0 asks for the

   * data transmission.

   *

   * \param mpidata: `const mixMPI*` Pointer to a `mixMPI` instance.

   * \param pid: `int` Rank of the process that is transmitting data.

   * \return result: `int` An exit code (0 for success).

   */

  int mpisend(const mixMPI *mpidata);

#endif // MPI_VERSION

};

#endif // INCLUDE_OUTPUTS_H_