From 851949b646f878dd58ed3ba55976e35b24672cd9 Mon Sep 17 00:00:00 2001
From: bangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Thu, 16 Dec 2010 20:57:53 +0000
Subject: [PATCH] Use a better solver.

git-svn-id: https://svn.dealii.org/trunk@22980 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/examples/step-38/step-38.cc | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/deal.II/examples/step-38/step-38.cc b/deal.II/examples/step-38/step-38.cc
index 005b4fa875..b7e166250b 100755
--- a/deal.II/examples/step-38/step-38.cc
+++ b/deal.II/examples/step-38/step-38.cc
@@ -160,8 +160,6 @@ class LaplaceBeltrami
     DoFHandler<dim-1,dim>      dof_handler;
     MappingQ<dim-1, dim>       mapping;
 
-    ConstraintMatrix     matrix_constraints;
-
     SparsityPattern      sparsity_pattern;
     SparseMatrix<double> system_matrix;
   
@@ -228,14 +226,10 @@ void LaplaceBeltrami<dim>::setup_system ()
 	    << " degrees of freedom."
 	    << std::endl;
   
-  matrix_constraints.clear ();
-  matrix_constraints.close ();
-
   CompressedSparsityPattern csp (dof_handler.n_dofs(),
                                  dof_handler.n_dofs());
 
   DoFTools::make_sparsity_pattern (dof_handler, csp);
-  matrix_constraints.condense (csp);
 
   sparsity_pattern.copy_from (csp);
 
@@ -331,25 +325,20 @@ void LaplaceBeltrami<dim>::assemble_system ()
 				      system_matrix,
 				      solution,
 				      system_rhs,false);
-
-				   // condense matrices
-  matrix_constraints.condense (system_matrix);
-  matrix_constraints.condense (system_rhs);
 }
 
 
 template <int dim>
 void LaplaceBeltrami<dim>::solve () 
 {
-  SolverControl           solver_control (1000, 1e-7);
+  SolverControl           solver_control (solution.size(), 1e-7);
   SolverCG<>              cg (solver_control);
 
-  cg.solve (system_matrix, solution, system_rhs,
-	    PreconditionIdentity());
-
-
-  matrix_constraints.distribute (solution);
+  PreconditionSSOR<> preconditioner;
+  preconditioner.initialize(system_matrix, 1.2);
 
+  cg.solve (system_matrix, solution, system_rhs,
+	    preconditioner);
 }
 
 
-- 
2.39.5