From: Martin Kronbichler <kronbichler@lnm.mw.tum.de>
Date: Tue, 24 Nov 2020 16:50:56 +0000 (+0100)
Subject: Multigrid: Only call MGLevelObject::resize() if necessary
X-Git-Tag: v9.3.0-rc1~852^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e3745799974cab80ff95a09958477456e1b93f24;p=dealii.git

Multigrid: Only call MGLevelObject::resize() if necessary
---

diff --git a/include/deal.II/multigrid/multigrid.templates.h b/include/deal.II/multigrid/multigrid.templates.h
index 5459468171..b8a7f3ba6e 100644
--- a/include/deal.II/multigrid/multigrid.templates.h
+++ b/include/deal.II/multigrid/multigrid.templates.h
@@ -251,12 +251,17 @@ void
 Multigrid<VectorType>::cycle()
 {
   // The defect vector has been initialized by copy_to_mg. Now adjust the
-  // other vectors.
-  solution.resize(minlevel, maxlevel);
-  t.resize(minlevel, maxlevel);
-  if (cycle_type != v_cycle)
+  // other vectors. First out a check if we have the right number of levels.
+  if (solution.min_level() != minlevel || solution.max_level() != maxlevel)
+    {
+      solution.resize(minlevel, maxlevel);
+      t.resize(minlevel, maxlevel);
+    }
+  if (cycle_type != v_cycle &&
+      (defect2.min_level() != minlevel || defect2.max_level() != maxlevel))
     defect2.resize(minlevel, maxlevel);
 
+  // And now we go and reinit the vectors on the levels.
   for (unsigned int level = minlevel; level <= maxlevel; ++level)
     {
       // the vectors for level>minlevel will be overwritten by the apply()
@@ -280,10 +285,14 @@ void
 Multigrid<VectorType>::vcycle()
 {
   // The defect vector has been initialized by copy_to_mg. Now adjust the
-  // other vectors.
-  solution.resize(minlevel, maxlevel);
-  t.resize(minlevel, maxlevel);
+  // other vectors. First out a check if we have the right number of levels.
+  if (solution.min_level() != minlevel || solution.max_level() != maxlevel)
+    {
+      solution.resize(minlevel, maxlevel);
+      t.resize(minlevel, maxlevel);
+    }
 
+  // And now we go and reinit the vectors on the levels.
   for (unsigned int level = minlevel; level <= maxlevel; ++level)
     {
       solution[level].reinit(defect[level], level > minlevel);