From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Fri, 13 Jan 2017 22:29:50 +0000 (-0700)
Subject: Fix the polynomial degree the ABF element reports about itself.
X-Git-Tag: v8.5.0-rc1~242^2~2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e8180bc7c6e57bd241153fd8d0fb3b16b4784eb7;p=dealii.git

Fix the polynomial degree the ABF element reports about itself.

As stated in the original paper (http://www-users.math.umn.edu/~arnold/papers/vecquad.pdf),
section 5, and as also stated in our discussion of the PolynomialsABF element, the
ABF space of order 'r' actually contains polynomials of degree 'r+2'. Report this
accurately.

Without this, the computation of embedding matrices fails in 3d because we integrate
the least squares matrix terms with a quadrature formula of too low order.
---

diff --git a/source/fe/fe_abf.cc b/source/fe/fe_abf.cc
index 843310367d..1598d99317 100644
--- a/source/fe/fe_abf.cc
+++ b/source/fe/fe_abf.cc
@@ -45,7 +45,9 @@ FE_ABF<dim>::FE_ABF (const unsigned int deg)
   FE_PolyTensor<PolynomialsABF<dim>, dim> (
     deg,
     FiniteElementData<dim>(get_dpo_vector(deg),
-                           dim, deg+1, FiniteElementData<dim>::Hdiv),
+                           dim,
+                           deg+2,
+                           FiniteElementData<dim>::Hdiv),
     std::vector<bool>(PolynomialsABF<dim>::compute_n_pols(deg), true),
     std::vector<ComponentMask>(PolynomialsABF<dim>::compute_n_pols(deg),
                                std::vector<bool>(dim,true))),