improve documentation of MGTransferMatrixFree::interpolate_to_mg()

diff --git a/include/deal.II/multigrid/mg_transfer_matrix_free.h b/include/deal.II/multigrid/mg_transfer_matrix_free.h
index d612a6f43a8ff720d2bda7f2d5c989e71aba0a68..ac0c9388666d35fabfead8e1490cc1cd8d8a7c35 100644 (file)
--- a/include/deal.II/multigrid/mg_transfer_matrix_free.h
+++ b/include/deal.II/multigrid/mg_transfer_matrix_free.h
@@ -156,8 +156,11 @@ public:
    * Restrict fine-mesh field @p src to each multigrid level in @p dof_handler and
    * store the result in @p dst.
    *
-   * If @p dst is empty or has incorrect locally owned size, it will be
-   * resized to locally relevant vectors on each level.
+   * The argument @p dst has to be initialized with the correct size according
+   * to the number of levels of the triangulation.
+   *
+   * If an inner vector of @p dst is empty or has incorrect locally owned size,
+   * it will be resized to locally relevant degrees of freedom on each level.
    */
   template <typename Number2, int spacedim>
   void