From: kronbichler <kronbichler@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Fri, 9 Jan 2009 18:40:46 +0000 (+0000)
Subject: Need to change the settings in AMG setup once again.
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=25ec05a9d38b06253493eb354a084a641405d476;p=dealii-svn.git

Need to change the settings in AMG setup once again.

git-svn-id: https://svn.dealii.org/trunk@18156 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/lac/source/trilinos_precondition.cc b/deal.II/lac/source/trilinos_precondition.cc
index 54ed93661d..a665e95c4d 100755
--- a/deal.II/lac/source/trilinos_precondition.cc
+++ b/deal.II/lac/source/trilinos_precondition.cc
@@ -567,8 +567,29 @@ namespace TrilinosWrappers
       {
 	ML_Epetra::SetDefaults("SA",parameter_list);
 	parameter_list.set("smoother: type", "Chebyshev");
+
+				   // uncoupled mode gives a lot of warnings
+				   // when there are too many entries per
+				   // row and aggreggation gets complicated,
+				   // but MIS does not work if too few
+				   // elements are located on one
+				   // processor. work around these warnings
+				   // by choosing the different strategies
+				   // in different situations: for low
+				   // order, always use the standard choice
+				   // uncoupled. if higher order, use
+				   // Uncoupled with few dofs and MIS
+				   // with many dofs per processor
+				   // 
+				   // TODO: Maybe there are some better
+				   // options?
 	if (additional_data.higher_order_elements)
-	  parameter_list.set("aggregation: type", "Uncoupled-MIS");
+	  {
+	    if (matrix.local_size() < 5000)
+	      parameter_list.set("aggregation: type", "Uncoupled");
+	    else
+	      parameter_list.set("aggregation: type", "MIS");
+	  }
       }
     else
       {