From 56cb89850f196d5d92b6a098dd6531614c2ed5c3 Mon Sep 17 00:00:00 2001
From: Sebastian Kinnewig <kinnewig@ifam.uni-hannover.de>
Date: Fri, 2 Feb 2024 11:35:56 +0100
Subject: [PATCH] Make TpetraWrapps::Vector compatible with BlockVectorBase.

---
 include/deal.II/lac/trilinos_tpetra_vector.h  | 30 +++++++++++++++++++
 .../lac/trilinos_tpetra_vector.templates.h    |  2 ++
 .../trilinos_tpetra_block_sparse_matrix.cc    | 12 --------
 3 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/include/deal.II/lac/trilinos_tpetra_vector.h b/include/deal.II/lac/trilinos_tpetra_vector.h
index 0b9a2d3c16..6018ff6fa0 100644
--- a/include/deal.II/lac/trilinos_tpetra_vector.h
+++ b/include/deal.II/lac/trilinos_tpetra_vector.h
@@ -208,6 +208,34 @@ namespace LinearAlgebra
                        << "An error with error number " << arg1
                        << " occurred while calling a Trilinos function");
 
+        /*
+         * Access to a an element that is not (locally-)owned.
+         *
+         * @ingroup Exceptions
+         */
+        DeclException4(
+          ExcAccessToNonLocalElement,
+          size_type,
+          size_type,
+          size_type,
+          size_type,
+          << "You are trying to access element " << arg1
+          << " of a distributed vector, but this element is not stored "
+          << "on the current processor. Note: There are " << arg2
+          << " elements stored "
+          << "on the current processor from within the range [" << arg3 << ','
+          << arg4 << "] but Trilinos vectors need not store contiguous "
+          << "ranges on each processor, and not every element in "
+          << "this range may in fact be stored locally."
+          << "\n\n"
+          << "A common source for this kind of problem is that you "
+          << "are passing a 'fully distributed' vector into a function "
+          << "that needs read access to vector elements that correspond "
+          << "to degrees of freedom on ghost cells (or at least to "
+          << "'locally active' degrees of freedom that are not also "
+          << "'locally owned'). You need to pass a vector that has these "
+          << "elements as ghost entries.");
+
       private:
         /**
          * Point to the vector we are referencing.
@@ -261,6 +289,8 @@ namespace LinearAlgebra
       using real_type  = typename numbers::NumberTraits<Number>::real_type;
       using size_type  = types::global_dof_index;
       using reference  = internal::VectorReference<Number, MemorySpace>;
+      using const_reference =
+        const internal::VectorReference<Number, MemorySpace>;
       using MapType =
         Tpetra::Map<int, dealii::types::signed_global_dof_index, NodeType>;
       using VectorType = Tpetra::
diff --git a/include/deal.II/lac/trilinos_tpetra_vector.templates.h b/include/deal.II/lac/trilinos_tpetra_vector.templates.h
index db6cc93ed5..c48c17e7de 100644
--- a/include/deal.II/lac/trilinos_tpetra_vector.templates.h
+++ b/include/deal.II/lac/trilinos_tpetra_vector.templates.h
@@ -182,6 +182,7 @@ namespace LinearAlgebra
           0, 0, Utilities::Trilinos::tpetra_comm_self()));
       has_ghost  = false;
       compressed = true;
+      nonlocal_vector.reset();
     }
 
 
@@ -1066,6 +1067,7 @@ namespace LinearAlgebra
     }
 
 
+
     template <typename Number, typename MemorySpace>
     MPI_Comm
     Vector<Number, MemorySpace>::mpi_comm() const
diff --git a/source/lac/trilinos_tpetra_block_sparse_matrix.cc b/source/lac/trilinos_tpetra_block_sparse_matrix.cc
index fafcebe325..283dad3bda 100644
--- a/source/lac/trilinos_tpetra_block_sparse_matrix.cc
+++ b/source/lac/trilinos_tpetra_block_sparse_matrix.cc
@@ -52,18 +52,6 @@ namespace LinearAlgebra
     BlockSparseMatrix<double>::Tvmult(
       TpetraWrappers::BlockVector<double> &,
       const TpetraWrappers::BlockVector<double> &) const;
-
-    template void
-    BlockSparseMatrix<double>::vmult(
-      ::dealii::BlockVector<double> &,
-      const ::dealii::BlockVector<double> &) const;
-
-    template void
-    BlockSparseMatrix<double>::Tvmult(
-      ::dealii::BlockVector<double> &,
-      const ::dealii::BlockVector<double> &) const;
-
-
   } // namespace TpetraWrappers
 } // namespace LinearAlgebra
 #  endif // DOXYGEN
-- 
2.39.5