WorkStream: add a note on hp-FEM

diff --git a/include/deal.II/base/work_stream.h b/include/deal.II/base/work_stream.h
index a9249612448ef4c795adf5154f7ed80da7c35dd1..9345b433cb9558e01c6872b899374d3c46f3fca3 100644 (file)
--- a/include/deal.II/base/work_stream.h
+++ b/include/deal.II/base/work_stream.h
@@ -126,6 +126,17 @@ DEAL_II_NAMESPACE_OPEN
  * unused and may be re-used for the next invocation of the worker function,
  * on this or another thread.
  *
+ * The member variables in ScratchData and CopyData can be accessed
+ * independently of other concurrent uses of copies of these data structures.
+ * Therefore, it is perfectly fine to resize auxiliary data structures
+ * associated with ScratchData and CopyData to different lengths on each cell.
+ * For example, a vector holding densities at each quadrature point which is used with
+ * LocalIntegrators::L2::weighted_mass_matrix() to assemble the local matrix
+ * could be resized to the corresponding number of quadrature points of the
+ * current cell in hp::DoFHandler. Similarly, local stiffness matrix in
+ * CopyData can be resized in accordance with the number of local DoFs on the
+ * current cell.
+ *
  * The functions in this namespace only really work in parallel when
  * multithread mode was selected during deal.II configuration. Otherwise they
  * simply work on each item sequentially.