ceph/src/boost/libs/mpi/include/boost/mpi/collectives/scatterv.hpp

   1 // Copyright (C) 2011 Júlio Hoffimann.
   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 4.6. Scatterv
   8 #ifndef BOOST_MPI_SCATTERV_HPP
   9 #define BOOST_MPI_SCATTERV_HPP
  10
  11 #include <boost/mpi/exception.hpp>
  12 #include <boost/mpi/datatype.hpp>
  13 #include <vector>
  14 #include <boost/mpi/packed_oarchive.hpp>
  15 #include <boost/mpi/packed_iarchive.hpp>
  16 #include <boost/mpi/detail/point_to_point.hpp>
  17 #include <boost/mpi/communicator.hpp>
  18 #include <boost/mpi/environment.hpp>
  19 #include <boost/assert.hpp>
  20
  21 namespace boost { namespace mpi {
  22
  23 namespace detail {
  24   // We're scattering from the root for a type that has an associated MPI
  25   // datatype, so we'll use MPI_Scatterv to do all of the work.
  26   template<typename T>
  27   void
  28   scatterv_impl(const communicator& comm, const T* in_values, const int* sizes,
  29                 const int* displs, T* out_values, int out_size, int root, mpl::true_)
  30   {
  31     MPI_Datatype type = get_mpi_datatype<T>(*in_values);
  32     BOOST_MPI_CHECK_RESULT(MPI_Scatterv,
  33                            (const_cast<T*>(in_values), const_cast<int*>(sizes),
  34                             const_cast<int*>(displs), type,
  35                             out_values, out_size, type, root, comm));
  36   }
  37
  38   // We're scattering from a non-root for a type that has an associated MPI
  39   // datatype, so we'll use MPI_Scatterv to do all of the work.
  40   template<typename T>
  41   void
  42   scatterv_impl(const communicator& comm, T* out_values, int out_size, int root,
  43                mpl::true_)
  44   {
  45     MPI_Datatype type = get_mpi_datatype<T>(*out_values);
  46     BOOST_MPI_CHECK_RESULT(MPI_Scatterv,
  47                            (0, 0, 0, type,
  48                             out_values, out_size, type,
  49                             root, comm));
  50   }
  51
  52   // We're scattering from the root for a type that does not have an
  53   // associated MPI datatype, so we'll need to serialize
  54   // it. Unfortunately, this means that we cannot use MPI_Scatterv, so
  55   // we'll just have the root send individual messages to the other
  56   // processes.
  57   template<typename T>
  58   void
  59   scatterv_impl(const communicator& comm, const T* in_values, const int* sizes,
  60                 const int* displs, T* out_values, int out_size, int root, mpl::false_)
  61   {
  62     int tag = environment::collectives_tag();
  63     int nprocs = comm.size();
  64
  65     for (int dest = 0; dest < nprocs; ++dest) {
  66       if (dest == root) {
  67         // Our own values will never be transmitted: just copy them.
  68         std::copy(in_values + displs[dest],
  69                   in_values + displs[dest] + out_size, out_values);
  70       } else {
  71         // Send archive
  72         packed_oarchive oa(comm);
  73         for (int i = 0; i < sizes[dest]; ++i)
  74           oa << in_values[ displs[dest] + i ];
  75         detail::packed_archive_send(comm, dest, tag, oa);
  76       }
  77     }
  78   }
  79
  80   // We're scattering to a non-root for a type that does not have an
  81   // associated MPI datatype, so we'll need to de-serialize
  82   // it. Unfortunately, this means that we cannot use MPI_Scatterv, so
  83   // we'll just have all of the non-root nodes send individual
  84   // messages to the root.
  85   template<typename T>
  86   void
  87   scatterv_impl(const communicator& comm, T* out_values, int out_size, int root,
  88                mpl::false_)
  89   {
  90     int tag = environment::collectives_tag();
  91
  92     packed_iarchive ia(comm);
  93     MPI_Status status;
  94     detail::packed_archive_recv(comm, root, tag, ia, status);
  95     for (int i = 0; i < out_size; ++i)
  96       ia >> out_values[i];
  97   }
  98 } // end namespace detail
  99
 100 template<typename T>
 101 void
 102 scatterv(const communicator& comm, const T* in_values,
 103          const std::vector<int>& sizes, const std::vector<int>& displs,
 104          T* out_values, int out_size, int root)
 105 {
 106   int rank = comm.rank();
 107   if (rank == root)
 108     detail::scatterv_impl(comm, in_values, &sizes[0], &displs[0],
 109                           out_values, out_size, root, is_mpi_datatype<T>());
 110   else
 111     detail::scatterv_impl(comm, out_values, out_size, root,
 112                           is_mpi_datatype<T>());
 113 }
 114
 115 template<typename T>
 116 void
 117 scatterv(const communicator& comm, const std::vector<T>& in_values,
 118          const std::vector<int>& sizes, const std::vector<int>& displs,
 119          T* out_values, int out_size, int root)
 120 {
 121   if (comm.rank() == root)
 122     ::boost::mpi::scatterv(comm, &in_values[0], sizes, displs,
 123                            out_values, out_size, root);
 124   else
 125     ::boost::mpi::scatterv(comm, static_cast<const T*>(0), sizes, displs,
 126                            out_values, out_size, root);
 127 }
 128
 129 template<typename T>
 130 void scatterv(const communicator& comm, T* out_values, int out_size, int root)
 131 {
 132   BOOST_ASSERT(comm.rank() != root);
 133   detail::scatterv_impl(comm, out_values, out_size, root, is_mpi_datatype<T>());
 134 }
 135
 136 ///////////////////////
 137 // common use versions
 138 ///////////////////////
 139 template<typename T>
 140 void
 141 scatterv(const communicator& comm, const T* in_values,
 142          const std::vector<int>& sizes, T* out_values, int root)
 143 {
 144   int nprocs = comm.size();
 145   int myrank = comm.rank();
 146
 147   std::vector<int> displs(nprocs);
 148   for (int rank = 0, aux = 0; rank < nprocs; ++rank) {
 149     displs[rank] = aux;
 150     aux += sizes[rank];
 151   }
 152   ::boost::mpi::scatterv(comm, in_values, sizes, displs, out_values,
 153                          sizes[myrank], root);
 154 }
 155
 156 template<typename T>
 157 void
 158 scatterv(const communicator& comm, const std::vector<T>& in_values,
 159          const std::vector<int>& sizes, T* out_values, int root)
 160 {
 161   ::boost::mpi::scatterv(comm, &in_values[0], sizes, out_values, root);
 162 }
 163
 164 } } // end namespace boost::mpi
 165
 166 #endif // BOOST_MPI_SCATTERV_HPP