all_gather(const MPI_Comm &comm,
const T &object_to_send);
+ /**
+ * A generalization of the classic MPI_Gather 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 an object to send to the root process
+ * @param[in] root_process The process, which receives the objects from all processes.
+ * By default the process with rank 0 is the root process.
+ *
+ * @return The @p root_process receives a vector of objects, with size equal to the number of
+ * processes in the MPI communicator. Each entry contains the object
+ * received from the processor with the corresponding rank within the
+ * communicator. All other processes receive an empty vector.
+ *
+ * @author Benjamin Brands, 2017
+ */
+ template <typename T>
+ std::vector<T>
+ gather(const MPI_Comm &comm,
+ const T &object_to_send,
+ const unsigned int root_process=0);
#ifndef DOXYGEN
// declaration for an internal function that lives in mpi.templates.h
internal::all_reduce(MPI_MIN, ArrayView<const T>(values, N),
mpi_communicator, ArrayView<T>(minima, N));
}
+
+ template <typename T>
+ std::vector<T>
+ gather(const MPI_Comm &comm,
+ const T &object_to_send,
+ const unsigned int root_process)
+ {
+#ifndef DEAL_II_WITH_MPI
+ (void)comm;
+ (void)root_process;
+ std::vector<T> v(1, object_to_send);
+ return v;
+#else
+ const auto n_procs = dealii::Utilities::MPI::n_mpi_processes(comm);
+ const auto my_rank = dealii::Utilities::MPI::this_mpi_process(comm);
+
+ Assert(root_process < n_procs, ExcIndexRange(root_process,0,n_procs));
+
+ std::vector<char> buffer = Utilities::pack(object_to_send);
+ int n_local_data = buffer.size();
+
+ // Vector to store the size of loc_data_array for every process
+ // only the root process needs to allocate memory for that purpose
+ std::vector<int> size_all_data;
+ if (my_rank==root_process)
+ size_all_data.resize(n_procs,0);
+
+ // Exchanging the size of each buffer
+ int ierr = MPI_Gather(&n_local_data, 1, MPI_INT,
+ size_all_data.data(), 1, MPI_INT,
+ root_process, comm);
+ AssertThrowMPI(ierr);
+
+ // Now computing the displacement, relative to recvbuf,
+ // at which to store the incoming buffer; only for root
+ std::vector<int> rdispls;
+ if (my_rank==root_process)
+ {
+ rdispls.resize(n_procs,0);
+ for (unsigned int i=1; i<n_procs; ++i)
+ rdispls[i] = rdispls[i-1] + size_all_data[i-1];
+ }
+ // exchange the buffer:
+ std::vector<char> received_unrolled_buffer;
+ if (my_rank==root_process)
+ received_unrolled_buffer.resize(rdispls.back() + size_all_data.back());
+
+ ierr = MPI_Gatherv(buffer.data(), n_local_data, MPI_CHAR,
+ received_unrolled_buffer.data(), size_all_data.data(),
+ rdispls.data(), MPI_CHAR,
+ root_process, comm);
+ AssertThrowMPI(ierr);
+
+ std::vector<T> received_objects;
+
+ if (my_rank==root_process)
+ {
+ received_objects.resize(n_procs);
+
+ for (unsigned int i=0; i<n_procs; ++i)
+ {
+ const std::vector<char> local_buffer(received_unrolled_buffer.begin()+rdispls[i],
+ received_unrolled_buffer.begin()+rdispls[i]+size_all_data[i]);
+ received_objects[i] = Utilities::unpack<T>(local_buffer);
+ }
+ }
+ return received_objects;
+#endif
+ }
+
#endif
} // end of namespace MPI
} // end of namespace Utilities
: numbers::invalid_dof_index ;
const unsigned int my_rank = Utilities::MPI::this_mpi_process(communicator);
- const unsigned int n_ranks = Utilities::MPI::n_mpi_processes(communicator);
- // first gather all information on process 0
- const unsigned int gather_size = (my_rank==0)?n_ranks:1;
- std::vector<types::global_dof_index> global_dofs(gather_size);
-
- int ierr = MPI_Gather(&first_local_dof, 1, DEAL_II_DOF_INDEX_MPI_TYPE,
- &(global_dofs[0]), 1, DEAL_II_DOF_INDEX_MPI_TYPE, 0,
- communicator);
- AssertThrowMPI(ierr);
+ const std::vector<types::global_dof_index> global_dofs = Utilities::MPI::gather(communicator,first_local_dof,0);
if (my_rank == 0)
{
// now broadcast the result
int is_ascending = is_globally_ascending ? 1 : 0;
- ierr = MPI_Bcast(&is_ascending, 1, MPI_INT, 0, communicator);
+ int ierr = MPI_Bcast(&is_ascending, 1, MPI_INT, 0, communicator);
AssertThrowMPI(ierr);
return (is_ascending==1);
--- /dev/null
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2017 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 at
+// the top level of the deal.II distribution.
+//
+// ---------------------------------------------------------------------
+
+// Test for Utilities::MPI::gather
+
+#include "../tests.h"
+#include <deal.II/base/point.h>
+#include <deal.II/base/mpi.h>
+#include <vector>
+
+int main(int argc, char *argv[])
+{
+ Utilities::MPI::MPI_InitFinalize mpi_initialization(argc, argv, 1);
+
+ initlog();
+
+ unsigned int root_process=0;
+ auto n_procs = Utilities::MPI::n_mpi_processes(MPI_COMM_WORLD);
+ 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);
+
+ auto gathered_points = Utilities::MPI::gather(MPI_COMM_WORLD, local_points, root_process);
+
+ if (my_proc==root_process)
+ {
+ bool test_passed = true;
+ for (unsigned int i=0; i<n_procs; ++i)
+ {
+ if (gathered_points[i].size() != i+1)
+ {
+ test_passed = false;
+ deallog << "Error: Points received from rank " << i << " have wrong size. " << std::endl;
+ }
+ for (unsigned int p=0; p< gathered_points[i].size(); ++p)
+ if ( gathered_points[i][p][0] != (double) i ||
+ gathered_points[i][p][1] != (double) -i ||
+ gathered_points[i][p][2] != (double) p)
+ {
+ test_passed = false;
+ deallog << "Error with point " << p << " from rank " << i << std::endl;
+ }
+ }
+ if (test_passed)
+ deallog << "Test: ok" << std::endl;
+ else
+ deallog << "Test: FAILED" << std::endl;
+ }
+}
projects / dealii.git / commitdiff