From afe7dbb4e237d8623f6aee4b85f5d6c62e416fb0 Mon Sep 17 00:00:00 2001
From: Bruno Blais <blais.bruno@gmail.com>
Date: Tue, 20 Aug 2024 17:12:12 -0400
Subject: [PATCH] Remove all clang tidy warnings from the core library of Lethe
 (#1243)

Description
Since I have deployed the new CI action, we are able to identify many more alerts using clang sanitizer. This PR aims at removing the alerts from the core library of Lethe. We still have warnings when we compile with clang, but this will need an additional CI instance check.

Testing
All units tests and application tests should pass before this is merged.
---
 include/core/bdf.h                            | 10 ++--
 include/core/manifolds.h                      | 12 ++--
 include/core/parameters.h                     | 12 ++--
 include/core/parsed_function_custom.h         |  6 +-
 include/core/pvd_handler.h                    |  6 +-
 include/core/serial_solid.h                   |  7 ++-
 include/core/shape.h                          |  2 +-
 include/core/shape_parsing.h                  | 16 +++---
 include/core/simulation_control.h             | 29 ++++++----
 include/core/solid_base.h                     |  8 +--
 include/core/solutions_output.h               |  8 +--
 include/core/utilities.h                      | 14 ++---
 source/core/bdf.cc                            | 16 +++---
 source/core/lethe_grid_tools.cc               |  8 +--
 source/core/manifolds.cc                      | 16 +++---
 source/core/parameters.cc                     | 20 +++----
 source/core/parsed_function_custom.cc         |  7 ++-
 source/core/pvd_handler.cc                    |  9 ++-
 source/core/serial_solid.cc                   |  6 +-
 source/core/shape.cc                          |  2 +-
 source/core/shape_parsing.cc                  | 56 +++++++++----------
 source/core/simulation_control.cc             | 24 ++++----
 source/core/solid_base.cc                     |  8 +--
 source/core/solutions_output.cc               | 40 ++++++-------
 source/core/utilities.cc                      | 46 ++++++++-------
 tests/core/bdf_01.cc                          | 10 ++--
 tests/core/bdf_extrapolation_01.cc            | 20 ++++---
 .../lethe_grid_tool_mesh_cut_by_flat_2.cc     | 11 ++--
 .../lethe_grid_tool_mesh_cut_by_flat_3.cc     | 13 ++---
 tests/core/shape_composites.cc                | 10 ++--
 tests/core/table_read.cc                      | 13 ++---
 tests/core/vector_problem.cc                  | 15 ++---
 32 files changed, 242 insertions(+), 238 deletions(-)

diff --git a/include/core/bdf.h b/include/core/bdf.h
index 10f935761a..e8fb5ff6c3 100644
--- a/include/core/bdf.h
+++ b/include/core/bdf.h
@@ -50,7 +50,7 @@ using namespace dealii;
 Vector<double>
 calculate_bdf_coefficients(
   const Parameters::SimulationControl::TimeSteppingMethod method,
-  const std::vector<double>                               time_steps);
+  const std::vector<double>                              &time_steps);
 
 
 /**
@@ -78,10 +78,10 @@ calculate_bdf_coefficients(
  * calculation of BDF coefficients.
  */
 Vector<double>
-delta(const unsigned int   order,
-      const unsigned int   n,
-      const unsigned int   j,
-      const Vector<double> times);
+delta(const unsigned int    order,
+      const unsigned int    n,
+      const unsigned int    j,
+      const Vector<double> &times);
 
 
 
diff --git a/include/core/manifolds.h b/include/core/manifolds.h
index beeb57d6d1..fedf3fb701 100644
--- a/include/core/manifolds.h
+++ b/include/core/manifolds.h
@@ -186,19 +186,19 @@ attach_manifolds_to_triangulation(
  */
 void
 attach_cad_to_manifold(parallel::DistributedTriangulationBase<2> &triangulation,
-                       std::string                                cad_name,
-                       unsigned int                               manifold_id);
+                       const std::string                         &cad_name,
+                       const unsigned int                         manifold_id);
 
 void
 attach_cad_to_manifold(
   parallel::DistributedTriangulationBase<2, 3> &triangulation,
-  std::string                                   cad_name,
-  unsigned int                                  manifold_id);
+  const std::string                            &cad_name,
+  const unsigned int                            manifold_id);
 
 void
 attach_cad_to_manifold(parallel::DistributedTriangulationBase<3> &triangulation,
-                       std::string                                cad_name,
-                       unsigned int                               manifold_id);
+                       const std::string                         &cad_name,
+                       const unsigned int                         manifold_id);
 
 
 
diff --git a/include/core/parameters.h b/include/core/parameters.h
index a9423789c4..f9970e66df 100644
--- a/include/core/parameters.h
+++ b/include/core/parameters.h
@@ -384,12 +384,12 @@ namespace Parameters
     {}
 
     void
-    declare_parameters(ParameterHandler &prm,
-                       std::string       material_prefix,
-                       unsigned int      id);
+    declare_parameters(ParameterHandler  &prm,
+                       const std::string &material_prefix,
+                       unsigned int       id);
     void
     parse_parameters(ParameterHandler    &prm,
-                     std::string          material_prefix,
+                     const std::string   &material_prefix,
                      const unsigned int   id,
                      const Dimensionality dimensions);
 
@@ -815,8 +815,8 @@ namespace Parameters
     // z =2) value of the beam_orientation parameter
     unsigned int beam_orientation_coordinate;
 
-    // beam_direction shows the direction of laser beam (either in positive (1)
-    // or negative (0) direction
+    // beam_direction shows the direction of laser beam (either in positive
+    // (true) or negative (false) direction
     bool beam_direction;
 
     // Based on the laser beam orientation, the integer values of a
diff --git a/include/core/parsed_function_custom.h b/include/core/parsed_function_custom.h
index b175d0732e..35570b20c8 100644
--- a/include/core/parsed_function_custom.h
+++ b/include/core/parsed_function_custom.h
@@ -81,9 +81,9 @@ class ParsedFunctionCustom
    * @param[in] constants_list Constants used by the expressions
    */
   void
-  initialize(const std::string vnames,
-             const std::string expression,
-             const std::string constants_list);
+  initialize(const std::string &vnames,
+             const std::string &expression,
+             const std::string &constants_list);
 
   /**
    * @brief Evaluate all components at the evaluation point
diff --git a/include/core/pvd_handler.h b/include/core/pvd_handler.h
index 25b8663f22..141caa6aa3 100644
--- a/include/core/pvd_handler.h
+++ b/include/core/pvd_handler.h
@@ -35,7 +35,7 @@ class PVDHandler
    * @param filename Name of the file to which the PVDHandler content is save
    */
   void
-  save(std::string filename);
+  save(const std::string &filename);
 
   /**
    * @brief read Reads the content of a pvd times_and_names checpoint
@@ -43,10 +43,10 @@ class PVDHandler
    * @param filename Name of the file frin which the PVDHandler content is read
    */
   void
-  read(std::string filename);
+  read(const std::string &filename);
 
   void
-  append(double time, std::string pvtu_filename)
+  append(double time, const std::string &pvtu_filename)
   {
     times_and_names.push_back(
       std::pair<double, std::string>(time, pvtu_filename));
diff --git a/include/core/serial_solid.h b/include/core/serial_solid.h
index 757c0d7768..27d4f4a6b7 100644
--- a/include/core/serial_solid.h
+++ b/include/core/serial_solid.h
@@ -201,7 +201,8 @@ class SerialSolid
    * @param simulation_control The simulation control object
    */
   void
-  write_output_results(std::shared_ptr<SimulationControl> simulation_control);
+  write_output_results(
+    const std::shared_ptr<SimulationControl> &simulation_control);
 
   /**
    * @brief read solid base triangulation checkpoint and replaces the
@@ -211,7 +212,7 @@ class SerialSolid
    *
    */
   void
-  read_checkpoint(std::string prefix_name);
+  read_checkpoint(const std::string &prefix_name);
 
   /**
    * @brief write solid base triangulation checkpoint
@@ -219,7 +220,7 @@ class SerialSolid
    * @param prefix_name The prefix of the checkpoint of the simulation
    */
   void
-  write_checkpoint(std::string prefix_name);
+  write_checkpoint(const std::string &prefix_name);
 
 
 private:
diff --git a/include/core/shape.h b/include/core/shape.h
index 0a3ba533b3..a71dd71cdb 100644
--- a/include/core/shape.h
+++ b/include/core/shape.h
@@ -2680,7 +2680,7 @@ class RBFShape : public Shape<dim>
    * @param orientation the orientation of the shape with respect to each main
    * axis
    */
-  RBFShape(const std::string   shape_arguments_str,
+  RBFShape(const std::string  &shape_arguments_str,
            const Point<dim>   &position,
            const Tensor<1, 3> &orientation);
 
diff --git a/include/core/shape_parsing.h b/include/core/shape_parsing.h
index 0ae01de080..5fd019726d 100644
--- a/include/core/shape_parsing.h
+++ b/include/core/shape_parsing.h
@@ -33,8 +33,8 @@ namespace ShapeGenerator
    */
   template <int dim>
   std::shared_ptr<Shape<dim>>
-  initialize_shape(const std::string   type,
-                   const std::string   shape_arguments_str,
+  initialize_shape(const std::string  &type,
+                   const std::string  &shape_arguments_str,
                    const Point<dim>   &position,
                    const Tensor<1, 3> &orientation);
 
@@ -47,10 +47,10 @@ namespace ShapeGenerator
    */
   template <int dim>
   std::shared_ptr<Shape<dim>>
-  initialize_shape_from_vector(const std::string         type,
-                               const std::vector<double> shape_arguments,
-                               const Point<dim>         &position,
-                               const Tensor<1, 3>       &orientation);
+  initialize_shape_from_vector(const std::string         &type,
+                               const std::vector<double> &shape_arguments,
+                               const Point<dim>          &position,
+                               const Tensor<1, 3>        &orientation);
 
   /**
    * Initializes the shape from its type and a text file that contains the real
@@ -62,8 +62,8 @@ namespace ShapeGenerator
    */
   template <int dim>
   std::shared_ptr<Shape<dim>>
-  initialize_shape_from_file(const std::string   type,
-                             const std::string   file_name,
+  initialize_shape_from_file(const std::string  &type,
+                             const std::string  &file_name,
                              const Point<dim>   &position,
                              const Tensor<1, 3> &orientation);
 } // namespace ShapeGenerator
diff --git a/include/core/simulation_control.h b/include/core/simulation_control.h
index 757ac99005..08dd840459 100644
--- a/include/core/simulation_control.h
+++ b/include/core/simulation_control.h
@@ -165,7 +165,7 @@ class SimulationControl
    *
    **/
 
-  SimulationControl(const Parameters::SimulationControl param);
+  SimulationControl(const Parameters::SimulationControl &param);
 
   /**
    * @brief Pure virtual function to control the progression of the simulation.
@@ -472,23 +472,31 @@ class SimulationControl
     return bdf_coefs;
   }
 
-
+  /**
+   * @brief Save the simulation control information from the checkpoint file and updates the time step vector, the CFL value, the time and the iteration number.
+   *
+   * @param prefix The prefix of the checkpoint of the simulation
+   */
   void
-  save(std::string filename);
+  save(const std::string &prefix);
 
   /**
    * @brief Reads the simulation control information from the checkpoint file and updates the time step vector, the CFL value, the time and the iteration number.
+   *
+   * @param prefix The prefix of the checkpoint of the simulation
    */
   void
-  read(std::string filename);
+  read(const std::string &prefix);
 
   /**
    * @brief Reads and returns the simulation control information from the checkpoint file filename without updating the simulation control information.
    *
+   * @param prefix The prefix of the checkpoint of the simulation
+   *
    * @return A vector containing the last checkpointed file and time step.
    */
   std::vector<double>
-  get_checkpointed_simulation_control_info(std::string filename);
+  get_checkpointed_simulation_control_info(const std::string &prefix);
 };
 
 
@@ -518,7 +526,7 @@ class SimulationControlTransient : public SimulationControl
 
 
 public:
-  SimulationControlTransient(Parameters::SimulationControl param);
+  SimulationControlTransient(const Parameters::SimulationControl &param);
 
   virtual void
   print_progression(const ConditionalOStream &pcout) override;
@@ -543,7 +551,7 @@ class SimulationControlTransient : public SimulationControl
 class SimulationControlTransientDEM : public SimulationControlTransient
 {
 public:
-  SimulationControlTransientDEM(Parameters::SimulationControl param);
+  SimulationControlTransientDEM(const Parameters::SimulationControl &param);
 
   virtual void
   print_progression(const ConditionalOStream &pcout) override;
@@ -571,7 +579,8 @@ class SimulationControlTransientDynamicOutput
   calculate_time_step() override;
 
 public:
-  SimulationControlTransientDynamicOutput(Parameters::SimulationControl param);
+  SimulationControlTransientDynamicOutput(
+    const Parameters::SimulationControl &param);
 
 
   /**
@@ -585,7 +594,7 @@ class SimulationControlTransientDynamicOutput
 class SimulationControlSteady : public SimulationControl
 {
 public:
-  SimulationControlSteady(Parameters::SimulationControl param);
+  SimulationControlSteady(const Parameters::SimulationControl &param);
 
   virtual void
   print_progression(const ConditionalOStream &pcout) override;
@@ -606,7 +615,7 @@ class SimulationControlSteady : public SimulationControl
 class SimulationControlAdjointSteady : public SimulationControlTransient
 {
 public:
-  SimulationControlAdjointSteady(Parameters::SimulationControl param);
+  SimulationControlAdjointSteady(const Parameters::SimulationControl &param);
 
   virtual void
   print_progression(const ConditionalOStream &pcout) override;
diff --git a/include/core/solid_base.h b/include/core/solid_base.h
index 5cd4af9378..5bf12c55ca 100644
--- a/include/core/solid_base.h
+++ b/include/core/solid_base.h
@@ -101,14 +101,14 @@ class SolidBase
    * @brief Loads a solid triangulation from a restart file
    */
   void
-  load_triangulation(const std::string filename_tria);
+  load_triangulation(const std::string &filename_tria);
 
   /**
    * @brief Loads a particle handler in the fluid triangulation domain that holds the particles of the solid
    * according to a specific quadrature, and sets up dofs
    */
   void
-  load_particles(const std::string filename_part);
+  load_particles(const std::string &filename_part);
 
   /**
    * @return the reference to the std::shared_ptr of a Particles::ParticleHandler<spacedim> that contains the solid particle handler
@@ -220,13 +220,13 @@ class SolidBase
    * @brief read solid base triangulation checkpoint
    */
   void
-  read_checkpoint(std::string prefix_name);
+  read_checkpoint(const std::string &prefix_name);
 
   /**
    * @brief write solid base triangulation checkpoint
    */
   void
-  write_checkpoint(std::string prefix_name);
+  write_checkpoint(const std::string &prefix_name);
 
 
 private:
diff --git a/include/core/solutions_output.h b/include/core/solutions_output.h
index 27f5eb6667..ff4e08b93e 100644
--- a/include/core/solutions_output.h
+++ b/include/core/solutions_output.h
@@ -55,8 +55,8 @@ template <int dim, int spacedim = dim>
 void
 write_vtu_and_pvd(PVDHandler                            &pvd_handler,
                   const DataOutInterface<dim, spacedim> &data_out,
-                  const std::string                      folder,
-                  const std::string                      file_prefix,
+                  const std::string                     &folder,
+                  const std::string                     &file_prefix,
                   const double                           time,
                   const unsigned int                     iter,
                   const unsigned int                     group_files,
@@ -80,10 +80,10 @@ write_vtu_and_pvd(PVDHandler                            &pvd_handler,
 template <int dim>
 void
 write_boundaries_vtu(const DataOutFaces<dim> &data_out,
-                     const std::string        folder,
+                     const std::string       &folder,
                      const double             time,
                      const unsigned int       iter,
                      const MPI_Comm          &mpi_communicator,
-                     const std::string  file_prefix = std::string("boundaries"),
+                     const std::string &file_prefix = std::string("boundaries"),
                      const unsigned int digits      = 5);
 #endif
diff --git a/include/core/utilities.h b/include/core/utilities.h
index f890e9e3e6..1aeeb515b3 100644
--- a/include/core/utilities.h
+++ b/include/core/utilities.h
@@ -363,9 +363,9 @@ calculate_point_property_cahn_hilliard(const double phase_cahn_hilliard,
  * @param delimiter The delimiter used to read the table.
  */
 void
-fill_table_from_file(TableHandler     &table,
-                     const std::string file_name,
-                     const std::string delimiter = " ");
+fill_table_from_file(TableHandler      &table,
+                     const std::string &file_name,
+                     const std::string &delimiter = " ");
 
 /**
  * @brief function that read a file that was build from a dealii table and fill 2 vectors.
@@ -379,8 +379,8 @@ fill_table_from_file(TableHandler     &table,
  */
 void
 fill_vectors_from_file(std::map<std::string, std::vector<double>> &map,
-                       const std::string                           file_name,
-                       const std::string delimiter = " ");
+                       const std::string                          &file_name,
+                       const std::string &delimiter = " ");
 
 /**
  * @brief Function that read a file that was build from a dealii table and create a map with the key being the column name and the variable the vectors of data.
@@ -393,8 +393,8 @@ fill_vectors_from_file(std::map<std::string, std::vector<double>> &map,
 void
 fill_string_vectors_from_file(
   std::map<std::string, std::vector<std::string>> &map,
-  const std::string                                file_name,
-  const std::string                                delimiter = " ");
+  const std::string                               &file_name,
+  const std::string                               &delimiter = " ");
 
 /**
  * @brief Creates the simulation output folder
diff --git a/source/core/bdf.cc b/source/core/bdf.cc
index c974e39584..3f55d29a4e 100644
--- a/source/core/bdf.cc
+++ b/source/core/bdf.cc
@@ -20,10 +20,10 @@
 
 
 Vector<double>
-bdf_coefficients(const unsigned int p, const std::vector<double> dt)
+bdf_coefficients(const unsigned int p, const std::vector<double> &time_steps)
 {
   // There should be at least p time steps
-  assert(dt.size() >= p);
+  assert(time_steps.size() >= p);
 
   // Create a time table for the bdf formula
   Vector<double> times(p + 1);
@@ -31,7 +31,7 @@ bdf_coefficients(const unsigned int p, const std::vector<double> dt)
     {
       times[i] = 0.;
       for (unsigned int j = 0; j < i; ++j)
-        times[i] -= dt[j];
+        times[i] -= time_steps[j];
     }
 
   // The alphas are the bdf coefficients
@@ -54,7 +54,7 @@ bdf_coefficients(const unsigned int p, const std::vector<double> dt)
 Vector<double>
 calculate_bdf_coefficients(
   const Parameters::SimulationControl::TimeSteppingMethod method,
-  const std::vector<double>                               time_steps)
+  const std::vector<double>                              &time_steps)
 {
   switch (method)
     {
@@ -74,10 +74,10 @@ calculate_bdf_coefficients(
 }
 
 Vector<double>
-delta(const unsigned int   p,
-      const unsigned int   n,
-      const unsigned int   j,
-      const Vector<double> times)
+delta(const unsigned int    p,
+      const unsigned int    n,
+      const unsigned int    j,
+      const Vector<double> &times)
 {
   if (j == 0)
     {
diff --git a/source/core/lethe_grid_tools.cc b/source/core/lethe_grid_tools.cc
index 964849d66f..7a299c480b 100644
--- a/source/core/lethe_grid_tools.cc
+++ b/source/core/lethe_grid_tools.cc
@@ -913,7 +913,7 @@ LetheGridTools::find_cells_around_flat_cell(
            std::set<typename DoFHandler<dim>::active_cell_iterator>>
     &vertices_cell_map)
 {
-  TriaActiveIterator<DoFCellAccessor<dim, dim, 0>> starting_cell =
+  TriaActiveIterator<DoFCellAccessor<dim, dim, false>> starting_cell =
     find_cell_around_point_with_tree(dof_handler, cell->vertex(0));
 
   std::unordered_set<typename DoFHandler<dim>::active_cell_iterator,
@@ -1257,13 +1257,13 @@ LetheGridTools::find_particle_triangle_projection(
       vector_to_plane              = p_0 - particle_position;
 
       // A bool variable for region 0
-      bool region_zero = 0;
+      bool region_zero = false;
 
       // Check to see if the particle is located on the correct side (with
       // respect to the normal vector) of the triangle
       if (vector_to_plane * unit_normal > 0)
         {
-          unit_normal = -1.0 * unit_normal;
+          unit_normal *= -1.0;
         }
 
       double distance_squared = scalar_product(vector_to_plane, unit_normal);
@@ -1349,7 +1349,7 @@ LetheGridTools::find_particle_triangle_projection(
               if constexpr (dim == 2)
                 unit_normal_3d = tensor_nd_to_3d(unit_normal);
 
-              region_zero = 1;
+              region_zero = true;
             }
         }
       else
diff --git a/source/core/manifolds.cc b/source/core/manifolds.cc
index a3a61cb3fd..e3434e2310 100644
--- a/source/core/manifolds.cc
+++ b/source/core/manifolds.cc
@@ -160,16 +160,16 @@ attach_manifolds_to_triangulation(
 
 void
 attach_cad_to_manifold(parallel::DistributedTriangulationBase<2> &,
-                       std::string,
-                       unsigned int)
+                       const std::string &,
+                       const unsigned int)
 {
   throw std::runtime_error("IGES manifolds are not supported in 2D");
 }
 
 void
 attach_cad_to_manifold(parallel::DistributedTriangulationBase<2, 3> &,
-                       std::string,
-                       unsigned int)
+                       const std::string &,
+                       const unsigned int)
 {
   throw std::runtime_error("IGES manifolds are not supported in 2D/3D");
 }
@@ -177,8 +177,8 @@ attach_cad_to_manifold(parallel::DistributedTriangulationBase<2, 3> &,
 #ifdef DEAL_II_WITH_OPENCASCADE
 void
 attach_cad_to_manifold(parallel::DistributedTriangulationBase<3> &triangulation,
-                       std::string                                cad_name,
-                       unsigned int                               manifold_id)
+                       const std::string                         &cad_name,
+                       const unsigned int                         manifold_id)
 {
   TopoDS_Shape cad_surface = OpenCASCADE::read_IGES(cad_name, 1e-3);
 
@@ -207,8 +207,8 @@ attach_cad_to_manifold(parallel::DistributedTriangulationBase<3> &triangulation,
 #else
 void
 attach_cad_to_manifold(parallel::DistributedTriangulationBase<3> &,
-                       std::string,
-                       unsigned int)
+                       const std::string &,
+                       const unsigned int)
 {
   throw std::runtime_error(
     "IGES manifolds require DEAL_II to be compiled with OPENCASCADE");
diff --git a/source/core/parameters.cc b/source/core/parameters.cc
index 8368f6fbc2..2412e0dbe2 100644
--- a/source/core/parameters.cc
+++ b/source/core/parameters.cc
@@ -973,9 +973,9 @@ namespace Parameters
   }
 
   void
-  Material::declare_parameters(ParameterHandler &prm,
-                               std::string       material_prefix,
-                               unsigned int      id)
+  Material::declare_parameters(ParameterHandler  &prm,
+                               const std::string &material_prefix,
+                               unsigned int       id)
   {
     prm.enter_subsection(material_prefix + " " +
                          Utilities::int_to_string(id, 1));
@@ -1081,7 +1081,7 @@ namespace Parameters
 
   void
   Material::parse_parameters(ParameterHandler                &prm,
-                             std::string                      material_prefix,
+                             const std::string               &material_prefix,
                              const unsigned int               id,
                              const Parameters::Dimensionality dimensions)
   {
@@ -1671,7 +1671,7 @@ namespace Parameters
       op = prm.get("beam orientation");
       if (op == "x+")
         {
-          beam_direction                     = 1;
+          beam_direction                     = true;
           beam_orientation                   = BeamOrientation::x_plus;
           beam_orientation_coordinate        = 0;
           perpendicular_plane_coordinate_one = 1;
@@ -1680,7 +1680,7 @@ namespace Parameters
         }
       else if (op == "x-")
         {
-          beam_direction                     = 0;
+          beam_direction                     = false;
           beam_orientation                   = BeamOrientation::x_minus;
           beam_orientation_coordinate        = 0;
           perpendicular_plane_coordinate_one = 1;
@@ -1689,7 +1689,7 @@ namespace Parameters
         }
       else if (op == "y+")
         {
-          beam_direction                     = 1;
+          beam_direction                     = true;
           beam_orientation                   = BeamOrientation::y_plus;
           perpendicular_plane_coordinate_one = 0;
           beam_orientation_coordinate        = 1;
@@ -1698,7 +1698,7 @@ namespace Parameters
         }
       else if (op == "y-")
         {
-          beam_direction                     = 0;
+          beam_direction                     = false;
           beam_orientation                   = BeamOrientation::y_minus;
           perpendicular_plane_coordinate_one = 0;
           beam_orientation_coordinate        = 1;
@@ -1709,7 +1709,7 @@ namespace Parameters
         {
           if constexpr (dim == 3)
             {
-              beam_direction                     = 1;
+              beam_direction                     = true;
               beam_orientation                   = BeamOrientation::z_plus;
               perpendicular_plane_coordinate_one = 0;
               perpendicular_plane_coordinate_two = 1;
@@ -1722,7 +1722,7 @@ namespace Parameters
         {
           if constexpr (dim == 3)
             {
-              beam_direction                     = 0;
+              beam_direction                     = false;
               beam_orientation                   = BeamOrientation::z_minus;
               perpendicular_plane_coordinate_one = 0;
               perpendicular_plane_coordinate_two = 1;
diff --git a/source/core/parsed_function_custom.cc b/source/core/parsed_function_custom.cc
index 6d2570c00d..830dc75454 100644
--- a/source/core/parsed_function_custom.cc
+++ b/source/core/parsed_function_custom.cc
@@ -148,9 +148,10 @@ ParsedFunctionCustom<n_components>::parse_parameters(ParameterHandler &prm)
 
 template <int n_components>
 void
-ParsedFunctionCustom<n_components>::initialize(const std::string vnames,
-                                               const std::string expression,
-                                               const std::string constants_list)
+ParsedFunctionCustom<n_components>::initialize(
+  const std::string &vnames,
+  const std::string &expression,
+  const std::string &constants_list)
 {
   this->vnames         = vnames;
   this->expression     = expression;
diff --git a/source/core/pvd_handler.cc b/source/core/pvd_handler.cc
index f4128982c6..9969850bc0 100644
--- a/source/core/pvd_handler.cc
+++ b/source/core/pvd_handler.cc
@@ -6,21 +6,20 @@
 using namespace dealii;
 
 void
-PVDHandler::save(std::string prefix)
+PVDHandler::save(const std::string &prefix)
 {
   std::string   filename = prefix + ".pvdhandler";
   std::ofstream output(filename.c_str());
   output << times_and_names.size() << std::endl;
   output << "Time File" << std::endl;
-  for (unsigned int i = 0; i < times_and_names.size(); ++i)
+  for (const auto &time_name : times_and_names)
     {
-      output << times_and_names[i].first << " " << times_and_names[i].second
-             << std::endl;
+      output << time_name.first << " " << time_name.second << std::endl;
     }
 }
 
 void
-PVDHandler::read(std::string prefix)
+PVDHandler::read(const std::string &prefix)
 {
   times_and_names.clear();
   std::string   filename = prefix + ".pvdhandler";
diff --git a/source/core/serial_solid.cc b/source/core/serial_solid.cc
index da749b4a97..ea90160e41 100644
--- a/source/core/serial_solid.cc
+++ b/source/core/serial_solid.cc
@@ -472,7 +472,7 @@ SerialSolid<dim, spacedim>::move_solid_triangulation_with_displacement()
 template <int dim, int spacedim>
 void
 SerialSolid<dim, spacedim>::write_output_results(
-  std::shared_ptr<SimulationControl> simulation_control)
+  const std::shared_ptr<SimulationControl> &simulation_control)
 {
   if (!output_bool)
     return;
@@ -541,7 +541,7 @@ SerialSolid<dim, spacedim>::write_output_results(
 
 template <int dim, int spacedim>
 void
-SerialSolid<dim, spacedim>::write_checkpoint(std::string prefix)
+SerialSolid<dim, spacedim>::write_checkpoint(const std::string &prefix)
 {
   // Checkpoint the DOF Handler
   {
@@ -567,7 +567,7 @@ SerialSolid<dim, spacedim>::write_checkpoint(std::string prefix)
 
 template <int dim, int spacedim>
 void
-SerialSolid<dim, spacedim>::read_checkpoint(std::string prefix)
+SerialSolid<dim, spacedim>::read_checkpoint(const std::string &prefix)
 {
   // Import dof handler
   {
diff --git a/source/core/shape.cc b/source/core/shape.cc
index 33ee45ea9e..10494222dd 100644
--- a/source/core/shape.cc
+++ b/source/core/shape.cc
@@ -1638,7 +1638,7 @@ CompositeShape<dim>::set_layer_thickening(const double layer_thickening)
 }
 
 template <int dim>
-RBFShape<dim>::RBFShape(const std::string   shape_arguments_str,
+RBFShape<dim>::RBFShape(const std::string  &shape_arguments_str,
                         const Point<dim>   &position,
                         const Tensor<1, 3> &orientation)
   : Shape<dim>(1, position, orientation)
diff --git a/source/core/shape_parsing.cc b/source/core/shape_parsing.cc
index 489de687ef..af6c846be4 100644
--- a/source/core/shape_parsing.cc
+++ b/source/core/shape_parsing.cc
@@ -2,8 +2,8 @@
 
 template <int dim>
 std::shared_ptr<Shape<dim>>
-ShapeGenerator::initialize_shape(const std::string   type,
-                                 const std::string   shape_arguments_str,
+ShapeGenerator::initialize_shape(const std::string  &type,
+                                 const std::string  &shape_arguments_str,
                                  const Point<dim>   &position,
                                  const Tensor<1, 3> &orientation)
 {
@@ -32,10 +32,10 @@ ShapeGenerator::initialize_shape(const std::string   type,
 template <int dim>
 std::shared_ptr<Shape<dim>>
 ShapeGenerator::initialize_shape_from_vector(
-  const std::string         type,
-  const std::vector<double> shape_arguments,
-  const Point<dim>         &position,
-  const Tensor<1, 3>       &orientation)
+  const std::string         &type,
+  const std::vector<double> &shape_arguments,
+  const Point<dim>          &position,
+  const Tensor<1, 3>        &orientation)
 {
   std::shared_ptr<Shape<dim>> shape;
   if (type == "sphere")
@@ -153,8 +153,8 @@ ShapeGenerator::initialize_shape_from_vector(
 
 template <int dim>
 std::shared_ptr<Shape<dim>>
-ShapeGenerator::initialize_shape_from_file(const std::string   type,
-                                           const std::string   file_name,
+ShapeGenerator::initialize_shape_from_file(const std::string  &type,
+                                           const std::string  &file_name,
                                            const Point<dim>   &position,
                                            const Tensor<1, 3> &orientation)
 {
@@ -212,12 +212,10 @@ ShapeGenerator::initialize_shape_from_file(const std::string   type,
                   std::vector<std::string> list_of_words_base =
                     Utilities::split_string_list(line, ";");
                   std::vector<std::string> list_of_words_clean;
-                  for (unsigned int j = 0; j < list_of_words_base.size(); ++j)
+                  for (const auto &word : list_of_words_base)
                     {
-                      if (list_of_words_base[j] != "")
-                        {
-                          list_of_words_clean.push_back(list_of_words_base[j]);
-                        }
+                      if (word != "")
+                        list_of_words_clean.emplace_back(word);
                     }
                   if (parsing_shapes)
                     {
@@ -313,34 +311,34 @@ ShapeGenerator::initialize_shape_from_file(const std::string   type,
 }
 
 template std::shared_ptr<Shape<2>>
-ShapeGenerator::initialize_shape(const std::string   type,
-                                 const std::string   arguments,
+ShapeGenerator::initialize_shape(const std::string  &type,
+                                 const std::string  &arguments,
                                  const Point<2>     &position,
                                  const Tensor<1, 3> &orientation);
 template std::shared_ptr<Shape<3>>
-ShapeGenerator::initialize_shape(const std::string   type,
-                                 const std::string   arguments,
+ShapeGenerator::initialize_shape(const std::string  &type,
+                                 const std::string  &arguments,
                                  const Point<3>     &position,
                                  const Tensor<1, 3> &orientation);
 template std::shared_ptr<Shape<2>>
 ShapeGenerator::initialize_shape_from_vector(
-  const std::string         type,
-  const std::vector<double> shape_arguments,
-  const Point<2>           &position,
-  const Tensor<1, 3>       &orientation);
+  const std::string         &type,
+  const std::vector<double> &shape_arguments,
+  const Point<2>            &position,
+  const Tensor<1, 3>        &orientation);
 template std::shared_ptr<Shape<3>>
 ShapeGenerator::initialize_shape_from_vector(
-  const std::string         type,
-  const std::vector<double> shape_arguments,
-  const Point<3>           &position,
-  const Tensor<1, 3>       &orientation);
+  const std::string         &type,
+  const std::vector<double> &shape_arguments,
+  const Point<3>            &position,
+  const Tensor<1, 3>        &orientation);
 template std::shared_ptr<Shape<2>>
-ShapeGenerator::initialize_shape_from_file(const std::string   type,
-                                           const std::string   file_name,
+ShapeGenerator::initialize_shape_from_file(const std::string  &type,
+                                           const std::string  &file_name,
                                            const Point<2>     &position,
                                            const Tensor<1, 3> &orientation);
 template std::shared_ptr<Shape<3>>
-ShapeGenerator::initialize_shape_from_file(const std::string   type,
-                                           const std::string   file_name,
+ShapeGenerator::initialize_shape_from_file(const std::string  &type,
+                                           const std::string  &file_name,
                                            const Point<3>     &position,
                                            const Tensor<1, 3> &orientation);
diff --git a/source/core/simulation_control.cc b/source/core/simulation_control.cc
index 22ee3f0a24..facb934bfd 100644
--- a/source/core/simulation_control.cc
+++ b/source/core/simulation_control.cc
@@ -6,7 +6,7 @@
 #include <sstream>
 
 
-SimulationControl::SimulationControl(const Parameters::SimulationControl param)
+SimulationControl::SimulationControl(const Parameters::SimulationControl &param)
   : method(param.method)
   , assembly_method(param.method)
   , current_time(0)
@@ -146,7 +146,7 @@ SimulationControl::is_verbose_iteration()
 }
 
 void
-SimulationControl::save(std::string prefix)
+SimulationControl::save(const std::string &prefix)
 {
   std::string   filename = prefix + ".simulationcontrol";
   std::ofstream output(filename.c_str());
@@ -159,7 +159,7 @@ SimulationControl::save(std::string prefix)
 }
 
 void
-SimulationControl::read(std::string prefix)
+SimulationControl::read(const std::string &prefix)
 {
   std::string   filename = prefix + ".simulationcontrol";
   std::ifstream input(filename.c_str());
@@ -167,8 +167,8 @@ SimulationControl::read(std::string prefix)
 
   std::string buffer;
   std::getline(input, buffer);
-  for (unsigned int i = 0; i < time_step_vector.size(); ++i)
-    input >> buffer >> time_step_vector[i];
+  for (auto &time_step_value : time_step_vector)
+    input >> buffer >> time_step_value;
   input >> buffer >> CFL;
   input >> buffer >> current_time;
   input >> buffer >> iteration_number;
@@ -178,7 +178,8 @@ SimulationControl::read(std::string prefix)
 }
 
 std::vector<double>
-SimulationControl::get_checkpointed_simulation_control_info(std::string prefix)
+SimulationControl::get_checkpointed_simulation_control_info(
+  const std::string &prefix)
 {
   std::string   filename = prefix + ".simulationcontrol";
   std::ifstream input(filename.c_str());
@@ -210,7 +211,7 @@ SimulationControl::get_checkpointed_simulation_control_info(std::string prefix)
 }
 
 SimulationControlTransient::SimulationControlTransient(
-  Parameters::SimulationControl param)
+  const Parameters::SimulationControl &param)
   : SimulationControl(param)
   , adapt(param.adapt)
   , adaptative_time_step_scaling(param.adaptative_time_step_scaling)
@@ -287,7 +288,7 @@ SimulationControlTransient::calculate_time_step()
 }
 
 SimulationControlTransientDEM::SimulationControlTransientDEM(
-  Parameters::SimulationControl param)
+  const Parameters::SimulationControl &param)
   : SimulationControlTransient(param)
 {}
 
@@ -312,7 +313,8 @@ SimulationControlTransientDEM::print_progression(
 
 
 SimulationControlTransientDynamicOutput::
-  SimulationControlTransientDynamicOutput(Parameters::SimulationControl param)
+  SimulationControlTransientDynamicOutput(
+    const Parameters::SimulationControl &param)
   : SimulationControlTransient(param)
   , time_step_forced_output(false)
   // To be fixed for restarts
@@ -367,7 +369,7 @@ SimulationControlTransientDynamicOutput::is_output_iteration()
 
 
 SimulationControlSteady::SimulationControlSteady(
-  Parameters::SimulationControl param)
+  const Parameters::SimulationControl &param)
   : SimulationControl(param)
 {}
 
@@ -438,7 +440,7 @@ SimulationControlAdjointSteady::is_at_end()
 }
 
 SimulationControlAdjointSteady::SimulationControlAdjointSteady(
-  Parameters::SimulationControl param)
+  const Parameters::SimulationControl &param)
   : SimulationControlTransient(param)
 {}
 
diff --git a/source/core/solid_base.cc b/source/core/solid_base.cc
index ae36fe8fb1..7aa8e6fc1a 100644
--- a/source/core/solid_base.cc
+++ b/source/core/solid_base.cc
@@ -276,7 +276,7 @@ SolidBase<3, 3>::translate_grid(const Tensor<1, 3> translation)
 
 template <int dim, int spacedim>
 void
-SolidBase<dim, spacedim>::load_triangulation(const std::string filename_tria)
+SolidBase<dim, spacedim>::load_triangulation(const std::string &filename_tria)
 {
   // Load solid triangulation from given file
   // Currently we only load the triangulation without loading the particles,
@@ -393,7 +393,7 @@ SolidBase<dim, spacedim>::setup_particles()
 
 template <int dim, int spacedim>
 void
-SolidBase<dim, spacedim>::load_particles(const std::string filename_part)
+SolidBase<dim, spacedim>::load_particles(const std::string &filename_part)
 {
   // Setup particles handler
   setup_particles_handler();
@@ -717,7 +717,7 @@ SolidBase<dim, spacedim>::print_particle_positions()
 
 template <int dim, int spacedim>
 void
-SolidBase<dim, spacedim>::write_checkpoint(std::string prefix)
+SolidBase<dim, spacedim>::write_checkpoint(const std::string &prefix)
 {
   // First, manage the serialization of the particle information.
   // The particles are attached to the background triangulation and not
@@ -754,7 +754,7 @@ SolidBase<dim, spacedim>::write_checkpoint(std::string prefix)
 
 template <int dim, int spacedim>
 void
-SolidBase<dim, spacedim>::read_checkpoint(std::string prefix)
+SolidBase<dim, spacedim>::read_checkpoint(const std::string &prefix)
 {
   // Setup an un-refined triangulation before loading if we have a fully
   // distributed triangulation. If we have a fully distributed triangulation,
diff --git a/source/core/solutions_output.cc b/source/core/solutions_output.cc
index 9bd18eea6c..30458a4653 100644
--- a/source/core/solutions_output.cc
+++ b/source/core/solutions_output.cc
@@ -16,8 +16,8 @@ template <int dim, int spacedim>
 void
 write_vtu_and_pvd(PVDHandler                            &pvd_handler,
                   const DataOutInterface<dim, spacedim> &data_out,
-                  const std::string                      folder,
-                  const std::string                      file_prefix,
+                  const std::string                     &folder,
+                  const std::string                     &file_prefix,
                   const double                           time,
                   const unsigned int                     iter,
                   const unsigned int                     group_files,
@@ -73,11 +73,11 @@ write_vtu_and_pvd(PVDHandler                            &pvd_handler,
 template <int dim>
 void
 write_boundaries_vtu(const DataOutFaces<dim> &data_out_faces,
-                     const std::string        folder,
+                     const std::string       &folder,
                      const double,
                      const unsigned int iter,
                      const MPI_Comm    &mpi_communicator,
-                     const std::string  file_prefix,
+                     const std::string &file_prefix,
                      const unsigned int digits)
 {
   const int my_id = Utilities::MPI::this_mpi_process(mpi_communicator);
@@ -97,8 +97,8 @@ write_boundaries_vtu(const DataOutFaces<dim> &data_out_faces,
 template void
 write_vtu_and_pvd(PVDHandler                   &pvd_handler,
                   const DataOutInterface<1, 2> &data_out,
-                  const std::string             folder,
-                  const std::string             file_prefix,
+                  const std::string            &folder,
+                  const std::string            &file_prefix,
                   const double                  time,
                   const unsigned int            iter,
                   const unsigned int            group_files,
@@ -108,8 +108,8 @@ write_vtu_and_pvd(PVDHandler                   &pvd_handler,
 template void
 write_vtu_and_pvd(PVDHandler                   &pvd_handler,
                   const DataOutInterface<2, 2> &data_out,
-                  const std::string             folder,
-                  const std::string             file_prefix,
+                  const std::string            &folder,
+                  const std::string            &file_prefix,
                   const double                  time,
                   const unsigned int            iter,
                   const unsigned int            group_files,
@@ -119,8 +119,8 @@ write_vtu_and_pvd(PVDHandler                   &pvd_handler,
 template void
 write_vtu_and_pvd(PVDHandler                   &pvd_handler,
                   const DataOutInterface<2, 3> &data_out,
-                  const std::string             folder,
-                  const std::string             file_prefix,
+                  const std::string            &folder,
+                  const std::string            &file_prefix,
                   const double                  time,
                   const unsigned int            iter,
                   const unsigned int            group_files,
@@ -130,8 +130,8 @@ write_vtu_and_pvd(PVDHandler                   &pvd_handler,
 template void
 write_vtu_and_pvd(PVDHandler                   &pvd_handler,
                   const DataOutInterface<3, 3> &data_out,
-                  const std::string             folder,
-                  const std::string             file_prefix,
+                  const std::string            &folder,
+                  const std::string            &file_prefix,
                   const double                  time,
                   const unsigned int            iter,
                   const unsigned int            group_files,
@@ -141,8 +141,8 @@ write_vtu_and_pvd(PVDHandler                   &pvd_handler,
 template void
 write_vtu_and_pvd(PVDHandler                   &pvd_handler,
                   const DataOutInterface<0, 2> &data_out,
-                  const std::string             folder,
-                  const std::string             file_prefix,
+                  const std::string            &folder,
+                  const std::string            &file_prefix,
                   const double                  time,
                   const unsigned int            iter,
                   const unsigned int            group_files,
@@ -152,8 +152,8 @@ write_vtu_and_pvd(PVDHandler                   &pvd_handler,
 template void
 write_vtu_and_pvd(PVDHandler                   &pvd_handler,
                   const DataOutInterface<0, 3> &data_out,
-                  const std::string             folder,
-                  const std::string             file_prefix,
+                  const std::string            &folder,
+                  const std::string            &file_prefix,
                   const double                  time,
                   const unsigned int            iter,
                   const unsigned int            group_files,
@@ -163,18 +163,18 @@ write_vtu_and_pvd(PVDHandler                   &pvd_handler,
 
 template void
 write_boundaries_vtu(const DataOutFaces<2> &data_out_faces,
-                     const std::string      folder,
+                     const std::string     &folder,
                      const double           time,
                      const unsigned int     iter,
                      const MPI_Comm        &mpi_communicator,
-                     const std::string      file_prefix,
+                     const std::string     &file_prefix,
                      const unsigned int     digits);
 
 template void
 write_boundaries_vtu(const DataOutFaces<3> &data_out_faces,
-                     const std::string      folder,
+                     const std::string     &folder,
                      const double           time,
                      const unsigned int     iter,
                      const MPI_Comm        &mpi_communicator,
-                     const std::string      file_prefix,
+                     const std::string     &file_prefix,
                      const unsigned int     digits);
diff --git a/source/core/utilities.cc b/source/core/utilities.cc
index e2165c8e22..827d4eb4fd 100644
--- a/source/core/utilities.cc
+++ b/source/core/utilities.cc
@@ -29,14 +29,14 @@ make_table_scalars_vectors(
   if (display_scientific_notation)
     {
       table.set_scientific(independent_column_name, true);
-      for (unsigned int d = 0; d < dependent_column_names.size(); ++d)
-        table.set_scientific(dependent_column_names[d], true);
+      for (const auto &name : dependent_column_names)
+        table.set_scientific(name, true);
     }
   else
     {
       table.set_precision(independent_column_name, display_precision);
-      for (unsigned int d = 0; d < dependent_column_names.size(); ++d)
-        table.set_precision(dependent_column_names[d], display_precision);
+      for (const auto &name : dependent_column_names)
+        table.set_precision(name, display_precision);
     }
 
   return table;
@@ -212,9 +212,9 @@ make_table_tensors_scalars(
 }
 
 void
-fill_table_from_file(TableHandler     &table,
-                     const std::string file_name,
-                     const std::string delimiter)
+fill_table_from_file(TableHandler      &table,
+                     const std::string &file_name,
+                     const std::string &delimiter)
 {
   table.clear();
   std::ifstream myfile(file_name);
@@ -231,11 +231,11 @@ fill_table_from_file(TableHandler     &table,
       std::vector<std::string> list_of_words_base =
         Utilities::split_string_list(line, delimiter);
       std::vector<std::string> list_of_words_clean;
-      for (unsigned int i = 0; i < list_of_words_base.size(); ++i)
+      for (const auto &word : list_of_words_base)
         {
-          if (list_of_words_base[i] != "")
+          if (word != "")
             {
-              list_of_words_clean.push_back(list_of_words_base[i]);
+              list_of_words_clean.emplace_back(word);
             }
         }
       //  If it's the first line, we only initialize the variable names.
@@ -259,8 +259,8 @@ fill_table_from_file(TableHandler     &table,
 
 void
 fill_vectors_from_file(std::map<std::string, std::vector<double>> &map,
-                       std::string                                 file,
-                       const std::string                           delimiter)
+                       const std::string                          &file,
+                       const std::string                          &delimiter)
 {
   // fill a pair, first being a vector of vector name and the second being the
   // vector of vector associated with the vector name.
@@ -278,11 +278,11 @@ fill_vectors_from_file(std::map<std::string, std::vector<double>> &map,
       std::vector<std::string> list_of_words_base =
         Utilities::split_string_list(line, delimiter);
       std::vector<std::string> list_of_words_clean;
-      for (unsigned int i = 0; i < list_of_words_base.size(); ++i)
+      for (const auto &word : list_of_words_base)
         {
-          if (list_of_words_base[i] != "")
+          if (word != "")
             {
-              list_of_words_clean.push_back(list_of_words_base[i]);
+              list_of_words_clean.emplace_back(word);
             }
         }
       // check if the line is contained words or numbers.
@@ -291,7 +291,7 @@ fill_vectors_from_file(std::map<std::string, std::vector<double>> &map,
           line_of_data = Utilities::string_to_double(list_of_words_clean);
           for (unsigned int i = 0; i < line_of_data.size(); ++i)
             {
-              map[column_names[i]].push_back(line_of_data[i]);
+              map[column_names[i]].emplace_back(line_of_data[i]);
             }
         }
       else
@@ -313,8 +313,8 @@ fill_vectors_from_file(std::map<std::string, std::vector<double>> &map,
 void
 fill_string_vectors_from_file(
   std::map<std::string, std::vector<std::string>> &map,
-  std::string                                      file,
-  const std::string                                delimiter)
+  const std::string                               &file,
+  const std::string                               &delimiter)
 {
   std::ifstream myfile(file);
   AssertThrow(myfile, ExcFileNotOpen(file));
@@ -330,12 +330,10 @@ fill_string_vectors_from_file(
       std::vector<std::string> list_of_words_base =
         Utilities::split_string_list(line, delimiter);
       std::vector<std::string> list_of_words_clean;
-      for (unsigned int i = 0; i < list_of_words_base.size(); ++i)
+      for (const auto &word : list_of_words_base)
         {
-          if (list_of_words_base[i] != "")
-            {
-              list_of_words_clean.push_back(list_of_words_base[i]);
-            }
+          if (word != "")
+            list_of_words_clean.emplace_back(word);
         }
       // Check if it is the first line. If it is we assume it is the
       // column name.
@@ -344,7 +342,7 @@ fill_string_vectors_from_file(
           line_of_data = list_of_words_clean;
           for (unsigned int i = 0; i < line_of_data.size(); ++i)
             {
-              map[column_names[i]].push_back(line_of_data[i]);
+              map[column_names[i]].emplace_back(line_of_data[i]);
             }
         }
       else
diff --git a/tests/core/bdf_01.cc b/tests/core/bdf_01.cc
index e5b144c89d..6ce7104dc4 100644
--- a/tests/core/bdf_01.cc
+++ b/tests/core/bdf_01.cc
@@ -20,10 +20,11 @@ test()
   dt[3] = 0.4;
   dt[4] = 0.5;
   deallog << "Time steps ";
-  for (unsigned int i = 0; i < dt.size(); ++i)
+  for (const auto &dt_val : dt)
     {
-      deallog << dt[i] << " ";
+      deallog << dt_val << " ";
     }
+
   deallog << std::endl;
 
   Vector<double> order1_coefficients = calculate_bdf_coefficients(
@@ -40,10 +41,11 @@ test()
   Vector<double> order3_coefficients = calculate_bdf_coefficients(
     Parameters::SimulationControl::TimeSteppingMethod::bdf3, dt);
   deallog << "Order 3 : ";
-  for (unsigned int i = 0; i < order3_coefficients.size(); ++i)
+  for (const auto &coefficient : order3_coefficients)
     {
-      deallog << order3_coefficients[i] << " ";
+      deallog << coefficient << " ";
     }
+
   deallog << std::endl;
 }
 
diff --git a/tests/core/bdf_extrapolation_01.cc b/tests/core/bdf_extrapolation_01.cc
index 82062cdb09..6b11dd72be 100644
--- a/tests/core/bdf_extrapolation_01.cc
+++ b/tests/core/bdf_extrapolation_01.cc
@@ -56,10 +56,11 @@ test()
     deallog << "Order 1: ";
 
 
-    for (unsigned int v = 0; v < out_values.size(); ++v)
+    for (const auto &val : out_values)
       {
-        deallog << out_values[v] << " ";
+        deallog << val << " ";
       }
+
     deallog << std::endl;
   }
 
@@ -71,10 +72,11 @@ test()
     deallog << "Order 2 constant time steps: ";
 
 
-    for (unsigned int v = 0; v < out_values.size(); ++v)
+    for (const auto &val : out_values)
       {
-        deallog << out_values[v] << " ";
+        deallog << val << " ";
       }
+
     deallog << std::endl;
   }
 
@@ -86,10 +88,11 @@ test()
     deallog << "Order 2 variable time steps: ";
 
 
-    for (unsigned int v = 0; v < out_values.size(); ++v)
+    for (const auto &val : out_values)
       {
-        deallog << out_values[v] << " ";
+        deallog << val << " ";
       }
+
     deallog << std::endl;
   }
 
@@ -101,10 +104,11 @@ test()
     deallog << "Order 3 constant time steps: ";
 
 
-    for (unsigned int v = 0; v < out_values.size(); ++v)
+    for (const auto &val : out_values)
       {
-        deallog << out_values[v] << " ";
+        deallog << val << " ";
       }
+
     deallog << std::endl;
   }
 }
diff --git a/tests/core/lethe_grid_tool_mesh_cut_by_flat_2.cc b/tests/core/lethe_grid_tool_mesh_cut_by_flat_2.cc
index 84ded63d2d..2e6bb37b63 100644
--- a/tests/core/lethe_grid_tool_mesh_cut_by_flat_2.cc
+++ b/tests/core/lethe_grid_tool_mesh_cut_by_flat_2.cc
@@ -102,13 +102,12 @@ test()
             });
 
   Vector<double> subdomain(triangulation.n_active_cells());
-  for (unsigned int i = 0; i < cells_cut.size(); ++i)
+  for (auto &cell : cells_cut)
     {
-      cells_cut[i]->set_subdomain_id(1);
-      subdomain(cells_cut[i]->global_active_cell_index()) = 1;
-      deallog << "The cell with ID : "
-              << cells_cut[i]->global_active_cell_index() << " is cut "
-              << std::endl;
+      cell->set_subdomain_id(1);
+      subdomain(cell->global_active_cell_index()) = 1;
+      deallog << "The cell with ID : " << cell->global_active_cell_index()
+              << " is cut " << std::endl;
     }
 
   // Printing the final position for all the vertices
diff --git a/tests/core/lethe_grid_tool_mesh_cut_by_flat_3.cc b/tests/core/lethe_grid_tool_mesh_cut_by_flat_3.cc
index a3fcd88300..e265d4241e 100644
--- a/tests/core/lethe_grid_tool_mesh_cut_by_flat_3.cc
+++ b/tests/core/lethe_grid_tool_mesh_cut_by_flat_3.cc
@@ -100,14 +100,13 @@ test()
             });
 
 
-  for (unsigned int i = 0; i < cells_cut.size(); ++i)
+  for (auto &cell : cells_cut)
     {
-      cells_cut[i]->set_subdomain_id(1);
-      subdomain(cells_cut[i]->global_active_cell_index()) =
-        cells_cut[i]->global_active_cell_index();
-      deallog << "The cell with ID : "
-              << cells_cut[i]->global_active_cell_index() << " is cut "
-              << std::endl;
+      cell->set_subdomain_id(1);
+      subdomain(cell->global_active_cell_index()) =
+        cell->global_active_cell_index();
+      deallog << "The cell with ID : " << cell->global_active_cell_index()
+              << " is cut " << std::endl;
     }
 
     // Printing the final position for all the vertices
diff --git a/tests/core/shape_composites.cc b/tests/core/shape_composites.cc
index a1892dc8b1..d9ae15295e 100644
--- a/tests/core/shape_composites.cc
+++ b/tests/core/shape_composites.cc
@@ -30,11 +30,11 @@ test()
   shapes[1] = rectangle;
 
   // Creation of maps of operations
-  typedef std::map<
-    unsigned int,
-    std::tuple<CompositeShape<3>::BooleanOperation, unsigned int, unsigned int>>
-                                              operation_map;
-  typedef CompositeShape<3>::BooleanOperation boolean_operation;
+  using operation_map     = std::map<unsigned int,
+                                 std::tuple<CompositeShape<3>::BooleanOperation,
+                                            unsigned int,
+                                            unsigned int>>;
+  using boolean_operation = CompositeShape<3>::BooleanOperation;
 
   operation_map operation_union;
   operation_union[2] = std::make_tuple(boolean_operation::Union, 0, 1);
diff --git a/tests/core/table_read.cc b/tests/core/table_read.cc
index 7161c9696b..aa8886c1e8 100644
--- a/tests/core/table_read.cc
+++ b/tests/core/table_read.cc
@@ -52,16 +52,11 @@ test()
   std::map<std::string, std::vector<double>> vectors;
   fill_vectors_from_file(vectors, table_file_name);
 
-  for (std::map<std::string, std::vector<double>>::iterator it =
-         vectors.begin();
-       it != vectors.end();
-       ++it)
+  for (const auto &it : vectors)
     {
-      deallog << it->first << std::endl;
-      for (unsigned int j = 0; j < it->second.size(); ++j)
-        {
-          deallog << it->second[j] << std::endl;
-        }
+      deallog << it.first << std::endl;
+      for (const auto &j : it.second)
+        deallog << j << std::endl;
     }
 }
 
diff --git a/tests/core/vector_problem.cc b/tests/core/vector_problem.cc
index bcaedee2e3..8574225016 100644
--- a/tests/core/vector_problem.cc
+++ b/tests/core/vector_problem.cc
@@ -99,14 +99,12 @@ test()
 
   for (unsigned int d = 0; d < 3; ++d)
     {
-      for (auto j = index_set_velocity[d].begin();
-           j != index_set_velocity[d].end();
-           j++)
+      for (const auto &j : index_set_velocity[d])
         {
-          correction_norm += dummy_solution[*j] * dummy_solution[*j];
+          correction_norm += dummy_solution[j] * dummy_solution[j];
 
           max_correction =
-            std::max(max_correction, std::abs(dummy_solution[*j]));
+            std::max(max_correction, std::abs(dummy_solution[j]));
         }
     }
 
@@ -116,12 +114,11 @@ test()
   correction_norm = 0.0;
   max_correction  = DBL_MIN;
 
-  for (auto j = index_set_pressure[3].begin(); j != index_set_pressure[3].end();
-       j++)
+  for (const auto &j : index_set_pressure[3])
     {
-      correction_norm += dummy_solution[*j] * dummy_solution[*j];
+      correction_norm += dummy_solution[j] * dummy_solution[j];
 
-      max_correction = std::max(max_correction, std::abs(dummy_solution[*j]));
+      max_correction = std::max(max_correction, std::abs(dummy_solution[j]));
     }
 
   deallog << "||p||_L2 : " << std::sqrt(correction_norm) << std::endl;