From: David Wells <drwells@email.unc.edu>
Date: Tue, 7 May 2019 02:18:33 +0000 (-0400)
Subject: step-28: fix a bug with the first mesh cycle.
X-Git-Tag: v9.1.0-rc1~118^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F8024%2Fhead;p=dealii.git

step-28: fix a bug with the first mesh cycle.

Previously the first cycle converged in a single iteration since the
error is calculated to be zero.
---

diff --git a/examples/step-28/step-28.cc b/examples/step-28/step-28.cc
index e2d277abe0..20ee55437f 100644
--- a/examples/step-28/step-28.cc
+++ b/examples/step-28/step-28.cc
@@ -1570,7 +1570,9 @@ namespace Step28
     boost::io::ios_flags_saver restore_flags(std::cout);
     std::cout << std::setprecision(12) << std::fixed;
 
-    double k_eff_old = k_eff;
+    // We calculate the error below by the change in k_eff (i.e., the
+    // difference between k_eff_old,
+    double k_eff_old = 0.0;
 
     for (unsigned int cycle = 0; cycle < parameters.n_refinement_cycles;
          ++cycle)