boost/mpi/collectives/all_gather.hpp

   1 // Copyright (C) 2005-2006 Douglas Gregor <doug.gregor -at- gmail.com>.
   2
   3 // Use, modification and distribution is subject to the Boost Software
   4 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6
   7 // Message Passing Interface 1.1 -- Section 4.7. Gather-to-all
   8 #ifndef BOOST_MPI_ALL_GATHER_HPP
   9 #define BOOST_MPI_ALL_GATHER_HPP
  10
  11 #include <boost/mpi/exception.hpp>
  12 #include <boost/mpi/datatype.hpp>
  13 #include <vector>
  14 #include <boost/serialization/vector.hpp>
  15
  16 // all_gather falls back to gather+broadcast in some cases
  17 #include <boost/mpi/collectives/broadcast.hpp>
  18 #include <boost/mpi/collectives/gather.hpp>
  19
  20 namespace boost { namespace mpi {
  21
  22 namespace detail {
  23   // We're all-gathering for a type that has an associated MPI
  24   // datatype, so we'll use MPI_Gather to do all of the work.
  25   template<typename T>
  26   void
  27   all_gather_impl(const communicator& comm, const T* in_values, int n,
  28                   T* out_values, mpl::true_)
  29   {
  30     MPI_Datatype type = boost::mpi::get_mpi_datatype<T>(*in_values);
  31     BOOST_MPI_CHECK_RESULT(MPI_Allgather,
  32                            (const_cast<T*>(in_values), n, type,
  33                             out_values, n, type, comm));
  34   }
  35
  36   // We're all-gathering for a type that has no associated MPI
  37   // type. So, we'll do a manual gather followed by a broadcast.
  38   template<typename T>
  39   void
  40   all_gather_impl(const communicator& comm, const T* in_values, int n,
  41                   T* out_values, mpl::false_)
  42   {
  43     gather(comm, in_values, n, out_values, 0);
  44     broadcast(comm, out_values, comm.size() * n, 0);
  45   }
  46 } // end namespace detail
  47
  48 template<typename T>
  49 inline void
  50 all_gather(const communicator& comm, const T& in_value, T* out_values)
  51 {
  52   detail::all_gather_impl(comm, &in_value, 1, out_values, is_mpi_datatype<T>());
  53 }
  54
  55 template<typename T>
  56 void
  57 all_gather(const communicator& comm, const T& in_value,
  58            std::vector<T>& out_values)
  59 {
  60   out_values.resize(comm.size());
  61   ::boost::mpi::all_gather(comm, &in_value, 1, &out_values[0]);
  62 }
  63
  64 template<typename T>
  65 inline void
  66 all_gather(const communicator& comm, const T* in_values, int n, T* out_values)
  67 {
  68   detail::all_gather_impl(comm, in_values, n, out_values, is_mpi_datatype<T>());
  69 }
  70
  71 template<typename T>
  72 void
  73 all_gather(const communicator& comm, const T* in_values, int n,
  74            std::vector<T>& out_values)
  75 {
  76   out_values.resize(comm.size() * n);
  77   ::boost::mpi::all_gather(comm, in_values, n, &out_values[0]);
  78 }
  79
  80 } } // end namespace boost::mpi
  81
  82 #endif // BOOST_MPI_ALL_GATHER_HPP