From: Peter Munch <peterrmuench@gmail.com>
Date: Tue, 1 Feb 2022 09:19:42 +0000 (+0100)
Subject: MatrixFreeTools::compute_diagonal(): do not initialize vector
X-Git-Tag: v9.4.0-rc1~541^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3145931a4387adc54b0e40f3ed70fbb588140b8;p=dealii.git

MatrixFreeTools::compute_diagonal(): do not initialize vector
---

diff --git a/doc/news/changes/incompatibilities/20220201SchreterMunch b/doc/news/changes/incompatibilities/20220201SchreterMunch
new file mode 100644
index 0000000000..1069f242a8
--- /dev/null
+++ b/doc/news/changes/incompatibilities/20220201SchreterMunch
@@ -0,0 +1,7 @@
+Changed: The function MatrixFreeTools::compute_diagonal()
+does not initialize the output vector anymore. Users
+need to call MatrixFree:initialize_dof_vector() themselves.
+This change is required to be able to also support block
+vectors.
+<br>
+(Magdalena Schreter, Peter Munch, 2022/02/01)
diff --git a/include/deal.II/matrix_free/tools.h b/include/deal.II/matrix_free/tools.h
index ef1a1c5e1a..b8e608b083 100644
--- a/include/deal.II/matrix_free/tools.h
+++ b/include/deal.II/matrix_free/tools.h
@@ -795,9 +795,6 @@ namespace MatrixFreeTools
   {
     using VectorType = LinearAlgebra::distributed::Vector<Number>;
 
-    // initialize vector
-    matrix_free.initialize_dof_vector(diagonal_global, dof_no);
-
     int dummy = 0;
 
     matrix_free.template cell_loop<VectorType, int>(
diff --git a/tests/matrix_free/compute_diagonal_util.h b/tests/matrix_free/compute_diagonal_util.h
index 9f64e13871..e0da7eb793 100644
--- a/tests/matrix_free/compute_diagonal_util.h
+++ b/tests/matrix_free/compute_diagonal_util.h
@@ -101,6 +101,7 @@ public:
     double error_local_1, error_local_2, error_global;
 
     {
+      matrix_free.initialize_dof_vector(diagonal_global);
       MatrixFreeTools::compute_diagonal<dim,
                                         fe_degree,
                                         n_points,
@@ -118,6 +119,7 @@ public:
 
     {
       VectorType diagonal_global;
+      matrix_free.initialize_dof_vector(diagonal_global);
       MatrixFreeTools::compute_diagonal(matrix_free,
                                         diagonal_global,
                                         &Test::cell_function,