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 54ed93661d76925b9f3c961f5f99a4cff5fdf8a9..a665e95c4d855a9998d009016a974e283e67fa93 100755 (executable)
--- 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
       {