From: Peter Munch <peterrmuench@gmail.com>
Date: Wed, 21 Oct 2020 14:26:00 +0000 (+0200)
Subject: Partitioner + L:d:V: new constructor
X-Git-Tag: v9.3.0-rc1~982^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F11071%2Fhead;p=dealii.git

Partitioner + L:d:V: new constructor
---

diff --git a/include/deal.II/base/partitioner.h b/include/deal.II/base/partitioner.h
index 68a814b21c..b28f635ff8 100644
--- a/include/deal.II/base/partitioner.h
+++ b/include/deal.II/base/partitioner.h
@@ -204,6 +204,24 @@ namespace Utilities
        */
       Partitioner(const unsigned int size);
 
+      /**
+       * Constructor that takes the number of locally-owned degrees of freedom
+       * @p local_size and the number of ghost degrees of freedom @p ghost_size.
+       *
+       * The local index range is translated to global indices in an ascending
+       * and one-to-one fashion, i.e., the indices of process $p$ sit exactly
+       * between the indices of the processes $p-1$ and $p+1$, respectively.
+       *
+       * @note Setting the @p ghost_size variable to an appropriate value
+       *   provides memory space for the ghost data in a vector's memory
+       *   allocation as and allows access to it via local_element(). However,
+       *   the associated global indices must be handled externally in this
+       *   case.
+       */
+      Partitioner(const types::global_dof_index local_size,
+                  const types::global_dof_index ghost_size,
+                  const MPI_Comm                communicator);
+
       /**
        * Constructor with index set arguments. This constructor creates a
        * distributed layout based on a given communicators, an IndexSet
diff --git a/include/deal.II/lac/la_parallel_vector.h b/include/deal.II/lac/la_parallel_vector.h
index 16e1251a2d..904d337628 100644
--- a/include/deal.II/lac/la_parallel_vector.h
+++ b/include/deal.II/lac/la_parallel_vector.h
@@ -362,6 +362,24 @@ namespace LinearAlgebra
       reinit(
         const std::shared_ptr<const Utilities::MPI::Partitioner> &partitioner);
 
+      /**
+       * Initialize vector with @p local_size locally-owned and @p ghost_size
+       * ghost degrees of freedoms.
+       *
+       * @note In the created underlying partitioner, the local index range is
+       *   translated to global indices in an ascending and one-to-one fashion,
+       *   i.e., the indices of process $p$ sit exactly between the indices of
+       *   the processes $p-1$ and $p+1$, respectively. Setting the
+       *   @p ghost_size variable to an appropriate value provides memory space
+       *   for the ghost data in a vector's memory allocation as and allows
+       *   access to it via local_element(). However, the associated global
+       *   indices must be handled externally in this case.
+       */
+      void
+      reinit(const types::global_dof_index local_size,
+             const types::global_dof_index ghost_size,
+             const MPI_Comm                comm);
+
       /**
        * Swap the contents of this vector and the other vector @p v. One could
        * do this operation with a temporary variable and copying over the data
diff --git a/include/deal.II/lac/la_parallel_vector.templates.h b/include/deal.II/lac/la_parallel_vector.templates.h
index d406a1610a..6eed0cbbe8 100644
--- a/include/deal.II/lac/la_parallel_vector.templates.h
+++ b/include/deal.II/lac/la_parallel_vector.templates.h
@@ -439,6 +439,32 @@ namespace LinearAlgebra
 
 
 
+    template <typename Number, typename MemorySpaceType>
+    void
+    Vector<Number, MemorySpaceType>::reinit(
+      const types::global_dof_index local_size,
+      const types::global_dof_index ghost_size,
+      const MPI_Comm                comm)
+    {
+      clear_mpi_requests();
+
+      // check whether we need to reallocate
+      resize_val(local_size + ghost_size);
+
+      // delete previous content in import data
+      import_data.values.reset();
+      import_data.values_dev.reset();
+
+      // create partitioner
+      partitioner = std::make_shared<Utilities::MPI::Partitioner>(local_size,
+                                                                  ghost_size,
+                                                                  comm);
+
+      this->operator=(Number());
+    }
+
+
+
     template <typename Number, typename MemorySpaceType>
     template <typename Number2>
     void
diff --git a/source/base/partitioner.cc b/source/base/partitioner.cc
index 0af2c3fddb..aec6633bf7 100644
--- a/source/base/partitioner.cc
+++ b/source/base/partitioner.cc
@@ -58,6 +58,40 @@ namespace Utilities
 
 
 
+    Partitioner::Partitioner(const types::global_dof_index local_size,
+                             const types::global_dof_index ghost_size,
+                             const MPI_Comm                communicator)
+      : global_size(Utilities::MPI::sum<types::global_dof_index>(local_size,
+                                                                 communicator))
+      , locally_owned_range_data(global_size)
+      , local_range_data{0, local_size}
+      , n_ghost_indices_data(ghost_size)
+      , n_import_indices_data(0)
+      , n_ghost_indices_in_larger_set(0)
+      , my_pid(Utilities::MPI::this_mpi_process(communicator))
+      , n_procs(Utilities::MPI::n_mpi_processes(communicator))
+      , communicator(communicator)
+      , have_ghost_indices(true)
+    {
+      types::global_dof_index prefix_sum = 0;
+
+#ifdef DEAL_II_WITH_MPI
+      MPI_Exscan(&local_size,
+                 &prefix_sum,
+                 1,
+                 Utilities::MPI::internal::mpi_type_id(&prefix_sum),
+                 MPI_SUM,
+                 communicator);
+#endif
+
+      local_range_data = {prefix_sum, prefix_sum + local_size};
+
+      locally_owned_range_data.add_range(prefix_sum, prefix_sum + local_size);
+      locally_owned_range_data.compress();
+    }
+
+
+
     Partitioner::Partitioner(const IndexSet &locally_owned_indices,
                              const IndexSet &ghost_indices_in,
                              const MPI_Comm  communicator_in)