const T & object_to_send,
const unsigned int root_process = 0);
+ /**
+ * A generalization of the classic MPI_Scatter function, that accepts
+ * arbitrary data types T, as long as boost::serialize accepts T as an
+ * argument.
+ *
+ * @param[in] comm MPI communicator.
+ * @param[in] object_to_send a vector of objects, with size equal to the
+ * number of processes.
+ * @param[in] root_process The process, which sends the objects to all
+ * processes. By default the process with rank 0 is the root process.
+ *
+ * @return Every process receives an object from the root_process.
+ */
+ template <typename T>
+ T
+ scatter(const MPI_Comm & comm,
+ const std::vector<T> &object_to_send,
+ const unsigned int root_process = 0);
+
/**
* This function sends an object @p object_to_send from the process @p root_process
* to all other processes.
+ template <typename T>
+ T
+ scatter(const MPI_Comm & comm,
+ const std::vector<T> &objects_to_send,
+ const unsigned int root_process)
+ {
+# ifndef DEAL_II_WITH_MPI
+ (void)comm;
+ (void)root_process;
+ return objects_to_send[0];
+# else
+ const auto n_procs = dealii::Utilities::MPI::n_mpi_processes(comm);
+ const auto my_rank = dealii::Utilities::MPI::this_mpi_process(comm);
+
+ AssertIndexRange(root_process, n_procs);
+ AssertThrow(
+ my_rank != root_process || objects_to_send.size() == n_procs,
+ ExcMessage(
+ "The number of objects to be scattered must correspond to the number processes."));
+
+ std::vector<char> send_buffer;
+ std::vector<int> send_counts;
+ std::vector<int> send_displacements;
+
+ if (my_rank == root_process)
+ {
+ send_counts.resize(n_procs, 0);
+ send_displacements.resize(n_procs + 1, 0);
+
+ for (unsigned int i = 0; i < n_procs; ++i)
+ {
+ const auto packed_data = Utilities::pack(objects_to_send[i]);
+ send_buffer.insert(send_buffer.end(),
+ packed_data.begin(),
+ packed_data.end());
+ send_counts[i] = packed_data.size();
+ }
+
+ for (unsigned int i = 0; i < n_procs; ++i)
+ send_displacements[i + 1] = send_displacements[i] + send_counts[i];
+ }
+
+ int n_local_data;
+ MPI_Scatter(send_counts.data(),
+ 1,
+ MPI_INT,
+ &n_local_data,
+ 1,
+ MPI_INT,
+ root_process,
+ comm);
+
+ std::vector<char> recv_buffer(n_local_data);
+
+ MPI_Scatterv(send_buffer.data(),
+ send_counts.data(),
+ send_displacements.data(),
+ MPI_CHAR,
+ recv_buffer.data(),
+ n_local_data,
+ MPI_CHAR,
+ root_process,
+ comm);
+
+ return Utilities::unpack<T>(recv_buffer);
+# endif
+ }
+
+
template <typename T>
void
broadcast(T * buffer,
--- /dev/null
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2017 - 2018 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of deal.II.
+//
+// ---------------------------------------------------------------------
+
+// Test for Utilities::MPI::scatter
+
+#include <deal.II/base/mpi.h>
+#include <deal.II/base/point.h>
+
+#include <vector>
+
+#include "../tests.h"
+
+int
+main(int argc, char *argv[])
+{
+ Utilities::MPI::MPI_InitFinalize mpi_initialization(argc, argv, 1);
+
+ initlog();
+
+ const unsigned int root_process = 0;
+ const auto n_procs = Utilities::MPI::n_mpi_processes(MPI_COMM_WORLD);
+ const auto my_proc = Utilities::MPI::this_mpi_process(MPI_COMM_WORLD);
+
+ // Creating the local array of points
+ std::vector<Point<3>> local_points(my_proc + 1);
+ for (unsigned int i = 0; i < my_proc + 1; ++i)
+ local_points[i] = Point<3>(my_proc, -my_proc, i);
+
+ // send to process 0
+ const auto gathered_points =
+ Utilities::MPI::gather(MPI_COMM_WORLD, local_points, root_process);
+
+ // scatter from process 0
+ const auto scattered_points =
+ Utilities::MPI::scatter(MPI_COMM_WORLD, gathered_points, root_process);
+
+ int test_passed = 1;
+
+ if (scattered_points.size() != my_proc + 1)
+ {
+ test_passed = 0;
+ deallog << "Error: Points on rank " << my_proc << " have wrong size. "
+ << std::endl;
+ }
+ for (unsigned int p = 0; p < scattered_points.size(); ++p)
+ if (scattered_points[p][0] != (double)my_proc ||
+ scattered_points[p][1] != (double)-my_proc ||
+ scattered_points[p][2] != (double)p)
+ {
+ test_passed = 0;
+ deallog << "Error with point " << p << " on rank " << my_proc
+ << std::endl;
+ }
+
+ if (Utilities::MPI::min(test_passed, MPI_COMM_WORLD))
+ deallog << "Test: ok" << std::endl;
+ else
+ deallog << "Test: FAILED" << std::endl;
+}
projects / dealii.git / commitdiff