Does MatrixFree::initialize_dof_vector() set vector entries to zero?

[nfehn]

If I see it correctly, I could not find this information in the documentation, see
https://www.dealii.org/developer/doxygen/deal.II/classMatrixFree.html#a6389c1e91648d277bdd81af095b5296c

[kronbichler]

Yes, it does, because the function calls

dealii/include/deal.II/matrix_free/matrix_free.h

Lines 2266 to 2267 in baf78cb

	AssertIndexRange(comp, n_components());
	vec.reinit(dof_info[comp].vector_partitioner, task_info.communicator_sm);

which in turn does

dealii/include/deal.II/lac/la_parallel_vector.templates.h

Lines 661 to 662 in baf78cb

	// initialize to zero
	*this = Number();

Do you want to add this information to the documentation here:

dealii/include/deal.II/matrix_free/matrix_free.h

Lines 1525 to 1547 in baf78cb

	* Initialize function for a general vector. The length of the vector is
	* equal to the total number of degrees in the DoFHandler. If the vector is
	* of class LinearAlgebra::distributed::Vector@<Number@>, the ghost entries
	* are set accordingly. For vector-valued problems with several DoFHandlers
	* underlying this class, the parameter @p vector_component defines which
	* component is to be used.
	*
	* For the vectors used with MatrixFree and in FEEvaluation, a vector needs
	* to hold all
	* @ref GlossLocallyActiveDof "locally active DoFs"
	* and also some of the
	* @ref GlossLocallyRelevantDof "locally relevant DoFs".
	* The selection of DoFs is such that one can read all degrees of freedom on
	* all locally relevant elements (locally active) plus the degrees of freedom
	* that constraints expand into from the locally owned cells. However, not
	* all locally relevant DoFs are stored because most of them would never be
	* accessed in matrix-vector products and result in too much data sent
	* around which impacts the performance.
	*/
	template <typename VectorType>
	void
	initialize_dof_vector(VectorType & vec,
	const unsigned int dof_handler_index = 0) const;