From f1f9065aa3aee80ed59e8bb1c5eb40364cac1084 Mon Sep 17 00:00:00 2001
From: Daniel Arndt <daniel.arndt@iwr.uni-heidelberg.de>
Date: Sun, 7 Oct 2018 04:37:41 +0200
Subject: [PATCH] Adress Wolfgang's comments a.k.a add more documentation and
 switches

---
 include/deal.II/base/utilities.h              |  8 ++++
 .../deal.II/lac/read_write_vector.templates.h | 45 ++++++++++---------
 include/deal.II/lac/trilinos_sparse_matrix.h  | 16 +++++++
 source/base/utilities.cc                      |  2 +
 4 files changed, 50 insertions(+), 21 deletions(-)

diff --git a/include/deal.II/base/utilities.h b/include/deal.II/base/utilities.h
index 71d05faf24..dc7414587e 100644
--- a/include/deal.II/base/utilities.h
+++ b/include/deal.II/base/utilities.h
@@ -888,6 +888,14 @@ namespace Utilities
     const Epetra_Comm &
     comm_self();
 
+    /**
+     * Return a Teuchos::Comm object needed for creation of Tpetra::Maps.
+     *
+     * If deal.II has been configured to use a compiler that does not support
+     * MPI then the resulting communicator will be a serial one. Otherwise,
+     * the communicator will correspond to MPI_COMM_SELF, i.e. a communicator
+     * that comprises only this one processor.
+     */
     const Teuchos::RCP<const Teuchos::Comm<int>> &
     tpetra_comm_self();
 
diff --git a/include/deal.II/lac/read_write_vector.templates.h b/include/deal.II/lac/read_write_vector.templates.h
index 87139aedd7..9da3c32e68 100644
--- a/include/deal.II/lac/read_write_vector.templates.h
+++ b/include/deal.II/lac/read_write_vector.templates.h
@@ -565,30 +565,33 @@ namespace LinearAlgebra
     Assert(size == 0 || values != nullptr, ExcInternalError("Export failed."));
     AssertDimension(size, stored_elements.n_elements());
 
-    if (operation == VectorOperation::insert)
-      {
-        for (size_type i = 0; i < size; ++i)
-          values[i] = new_values[i];
-      }
-    else if (operation == VectorOperation::add)
-      {
-        for (size_type i = 0; i < size; ++i)
-          values[i] += new_values[i];
-      }
-    else if (operation == VectorOperation::min)
+    switch (operation)
       {
-        for (size_type i = 0; i < size; ++i)
-          if (std::real(new_values[i]) - std::real(values[i]) < 0.0)
-            values[i] = new_values[i];
-      }
-    else if (operation == VectorOperation::max)
-      {
-        for (size_type i = 0; i < size; ++i)
-          if (std::real(new_values[i]) - std::real(values[i]) > 0.0)
+        case VectorOperation::insert:
+          for (size_type i = 0; i < size; ++i)
             values[i] = new_values[i];
+          break;
+
+        case VectorOperation::add:
+          for (size_type i = 0; i < size; ++i)
+            values[i] += new_values[i];
+          break;
+
+        case VectorOperation::min:
+          for (size_type i = 0; i < size; ++i)
+            if (std::real(new_values[i]) - std::real(values[i]) < 0.0)
+              values[i] = new_values[i];
+          break;
+
+        case VectorOperation::max:
+          for (size_type i = 0; i < size; ++i)
+            if (std::real(new_values[i]) - std::real(values[i]) > 0.0)
+              values[i] = new_values[i];
+          break;
+
+        default:
+          AssertThrow(false, ExcNotImplemented());
       }
-    else
-      AssertThrow(false, ExcNotImplemented());
   }
 
 
diff --git a/include/deal.II/lac/trilinos_sparse_matrix.h b/include/deal.II/lac/trilinos_sparse_matrix.h
index 2ae42c5ef1..368fc70a12 100644
--- a/include/deal.II/lac/trilinos_sparse_matrix.h
+++ b/include/deal.II/lac/trilinos_sparse_matrix.h
@@ -1576,6 +1576,9 @@ namespace TrilinosWrappers
      * initialized with the same IndexSet that was used for the column indices
      * of the matrix.
      *
+     * This function will be called when the underlying number type for the
+     * matrix object and the one one for the vector object are the same.
+     *
      * In case of a serial vector, this function will only work when
      * running on one processor, since the matrix object is inherently
      * distributed. Otherwise, an exception will be thrown.
@@ -1585,6 +1588,11 @@ namespace TrilinosWrappers
                                          TrilinosScalar>::value>::type
     vmult(VectorType &dst, const VectorType &src) const;
 
+    /**
+     * Same as the function above for the case that the underlying number type
+     * for the matrix object and the one for the vector object do not coincide.
+     * This case is not implemented. Calling it will result in an runtime error.
+     */
     template <typename VectorType>
     typename std::enable_if<!std::is_same<typename VectorType::value_type,
                                           TrilinosScalar>::value>::type
@@ -1599,12 +1607,20 @@ namespace TrilinosWrappers
      *
      * This function can be called with several types of vector objects,
      * see the discussion about @p VectorType in vmult().
+     *
+     * This function will be called when the underlying number type for the
+     * matrix object and the one one for the vector object are the same.
      */
     template <typename VectorType>
     typename std::enable_if<std::is_same<typename VectorType::value_type,
                                          TrilinosScalar>::value>::type
     Tvmult(VectorType &dst, const VectorType &src) const;
 
+    /**
+     * Same as the function above for the case that the underlying number type
+     * for the matrix object and the one for the vector object do not coincide.
+     * This case is not implemented. Calling it will result in an runtime error.
+     */
     template <typename VectorType>
     typename std::enable_if<!std::is_same<typename VectorType::value_type,
                                           TrilinosScalar>::value>::type
diff --git a/source/base/utilities.cc b/source/base/utilities.cc
index ff4d0d9573..d5f120192b 100644
--- a/source/base/utilities.cc
+++ b/source/base/utilities.cc
@@ -993,6 +993,8 @@ namespace Utilities
       return communicator;
     }
 
+
+
     const Epetra_Comm &
     comm_self()
     {
-- 
2.39.5