Boost C++ Libraries

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Function gather

boost::mpi::gather — Gather the values stored at every process into a vector at the root process.

Synopsis

// In header: <boost/mpi/collectives.hpp>


template<typename T> 
  void gather(const communicator & comm, const T & in_value, 
              std::vector< T > & out_values, int root);
template<typename T> 
  void gather(const communicator & comm, const T & in_value, T * out_values, 
              int root);
template<typename T> 
  void gather(const communicator & comm, const T & in_value, int root);
template<typename T> 
  void gather(const communicator & comm, const T * in_values, int n, 
              std::vector< T > & out_values, int root);
template<typename T> 
  void gather(const communicator & comm, const T * in_values, int n, 
              T * out_values, int root);
template<typename T> 
  void gather(const communicator & comm, const T * in_values, int n, int root);

Description

gather is a collective algorithm that collects the values stored at each process into a vector of values at the root process. This vector is indexed by the process number that the value came from. The type T of the values may be any type that is serializable or has an associated MPI data type.

When the type T has an associated MPI data type, this routine invokes MPI_Gather to gather the values.

Parameters:

`comm`	The communicator over which the gather will occur.
`in_value`	The value to be transmitted by each process. For gathering arrays of values, `in_values` points to storage for `n*comm`.size() values.
`out_values`	A vector or pointer to storage that will be populated with the values from each process, indexed by the process ID number. If it is a vector, it will be resized accordingly. For non-root processes, this parameter may be omitted. If it is still provided, however, it will be unchanged.
`root`	The process ID number that will collect the values. This value must be the same on all processes.