From ebd11be4de77df1aee13bc84c140962c4c17140d Mon Sep 17 00:00:00 2001
From: guido <guido@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Tue, 16 Apr 2002 14:24:09 +0000
Subject: [PATCH] Exception for missing prolongation matrices

git-svn-id: https://svn.dealii.org/trunk@5668 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/deal.II/include/multigrid/mg_transfer.h | 6 ++++++
 deal.II/deal.II/source/multigrid/multigrid.cc   | 4 +++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/deal.II/deal.II/include/multigrid/mg_transfer.h b/deal.II/deal.II/include/multigrid/mg_transfer.h
index 527d04b8a7..f76a4e8d65 100644
--- a/deal.II/deal.II/include/multigrid/mg_transfer.h
+++ b/deal.II/deal.II/include/multigrid/mg_transfer.h
@@ -136,6 +136,12 @@ class MGTransferPrebuilt : public Subscriptor // MGTransferBase<Vector<double> >
 		      OutVector &dst,
 		      const MGLevelObject<Vector<double> > &src) const;
 
+				     /**
+				      * Finite element does not
+				      * provide prolongation matrices.
+				      */
+    DeclException0(ExcNoProlongation);
+    
   private:
 
 				   /**
diff --git a/deal.II/deal.II/source/multigrid/multigrid.cc b/deal.II/deal.II/source/multigrid/multigrid.cc
index cc65bc9e1c..f7781ad870 100644
--- a/deal.II/deal.II/source/multigrid/multigrid.cc
+++ b/deal.II/deal.II/source/multigrid/multigrid.cc
@@ -83,7 +83,9 @@ void MGTransferPrebuilt::build_matrices (const MGDoFHandler<dim> &mg_dof)
 						 // this child
 		const FullMatrix<double> &prolongation
 		  = mg_dof.get_fe().prolongate(child);
-	    
+
+		Assert (prolongation.n() != 0, ExcNoProlongation());
+		
 		cell->child(child)->get_mg_dof_indices (dof_indices_child);
 
 						 // now tag the entries in the
-- 
2.39.5