From 32c6af9f3ec067eb8ea969b1778044592658db2b Mon Sep 17 00:00:00 2001
From: oliver <oliver@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Tue, 27 Jul 2004 14:08:49 +0000
Subject: [PATCH] Added some of the probably more important parameters to the
 class PreconditionLU.

git-svn-id: https://svn.dealii.org/trunk@9521 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/lac/include/lac/petsc_precondition.h | 36 ++++++++++++++++++--
 deal.II/lac/source/petsc_precondition.cc     | 18 +++++++++-
 2 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/deal.II/lac/include/lac/petsc_precondition.h b/deal.II/lac/include/lac/petsc_precondition.h
index 510fad9603..24a41a32db 100644
--- a/deal.II/lac/include/lac/petsc_precondition.h
+++ b/deal.II/lac/include/lac/petsc_precondition.h
@@ -533,9 +533,38 @@ namespace PETScWrappers
       struct AdditionalData
       {
                                            /**
-                                            * Constructor. 
+                                            * Constructor. (Default values
+					    * taken from function PCCreate_LU
+					    * of the PetSC lib.)
                                             */
-          AdditionalData ();
+          AdditionalData (const double pivoting = 1.e-6,
+			  const double zero_pivot = 1.e-12,
+			  const double damping = 0.0);
+
+                                           /**
+                                            * Determines, when Pivoting is
+					    * done during LU decomposition.
+					    * 0.0 indicates no pivoting,
+					    * and 1.0 complete pivoting.
+					    * Confer PetSC manual for more
+					    * details.
+                                            */
+          double pivoting;
+
+                                           /**
+                                            * Size at which smaller pivots
+					    * are declared to be zero.
+					    * Confer PetSC manual for more
+					    * details.
+					    */
+	  double zero_pivot;					    
+
+                                           /**
+                                            * This quantity is added to the
+					    * diagonal of the matrix during
+					    * factorisation.
+					    */
+	  double damping;
       };
 
                                        /**
@@ -550,7 +579,8 @@ namespace PETScWrappers
                                         * generates a compiler fault.
                                         */
       PreconditionLU (const MatrixBase     &matrix,
-		      const AdditionalData &additional_data = AdditionalData());
+		      const AdditionalData &additional_data = 
+		      AdditionalData(1.e-6, 1.e-12, 0.0));
       
     protected:
                                        /**
diff --git a/deal.II/lac/source/petsc_precondition.cc b/deal.II/lac/source/petsc_precondition.cc
index 836d439622..542257393b 100644
--- a/deal.II/lac/source/petsc_precondition.cc
+++ b/deal.II/lac/source/petsc_precondition.cc
@@ -259,7 +259,13 @@ namespace PETScWrappers
 /* ----------------- PreconditionLU -------------------- */
 
   PreconditionLU::AdditionalData::
-  AdditionalData ()
+  AdditionalData (const double pivoting,
+		  const double zero_pivot,
+		  const double damping)
+                  :
+                  pivoting (pivoting),
+                  zero_pivot (zero_pivot),
+		  damping (damping)
   {}
 
   
@@ -279,6 +285,16 @@ namespace PETScWrappers
                                      // preconditioner
     int ierr;
     ierr = PCSetType (pc, const_cast<char *>(PCLU));
+    AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+                                     // set flags as given
+    ierr = PCLUSetPivoting (pc, additional_data.pivoting);
+    AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+    ierr = PCLUSetZeroPivot (pc, additional_data.zero_pivot);
+    AssertThrow (ierr == 0, ExcPETScError(ierr));
+
+    ierr = PCLUSetDamping (pc, additional_data.damping);
     AssertThrow (ierr == 0, ExcPETScError(ierr));
   }
   
-- 
2.39.5