From: Wolfgang Bangerth <bangerth@math.tamu.edu>
Date: Thu, 12 Mar 2015 01:36:58 +0000 (-0500)
Subject: Improve what an exception says.
X-Git-Tag: v8.3.0-rc1~378^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aecc7be38cba05425d652aeab49f6c7de80fb01b;p=dealii.git

Improve what an exception says.

This happens to be a case one of my students ran into today. Again for #610.
---

diff --git a/include/deal.II/lac/sparse_ilu.h b/include/deal.II/lac/sparse_ilu.h
index d2e86ed571..aca55bf088 100644
--- a/include/deal.II/lac/sparse_ilu.h
+++ b/include/deal.II/lac/sparse_ilu.h
@@ -142,6 +142,17 @@ public:
                   double,
                   << "The strengthening parameter " << arg1
                   << " is not greater or equal than zero!");
+  /**
+   * Exception
+   */
+  DeclException1 (ExcZeroPivot,
+                  size_type,
+                  << "While computing the ILU decomposition, the algorithm "
+                  "found a zero pivot on the diagonal of row "
+                  << arg1
+                  << ". This must stop the ILU algorithm because it means "
+                  "that the matrix for which you try to compute a "
+                  "decomposition is singular.");
   //@}
 };
 
diff --git a/include/deal.II/lac/sparse_ilu.templates.h b/include/deal.II/lac/sparse_ilu.templates.h
index bb6e47871b..97113152e8 100644
--- a/include/deal.II/lac/sparse_ilu.templates.h
+++ b/include/deal.II/lac/sparse_ilu.templates.h
@@ -126,7 +126,7 @@ label_200:
       // now we have to deal with the diagonal element. in the book it is
       // located at position 'j', but here we use the convention of storing
       // the diagonal element first, so instead of j we use uptr[k]=ia[k]
-      Assert (luval[ia[k]] != 0, ExcInternalError());
+      Assert (luval[ia[k]] != 0, ExcZeroPivot(k));
 
       luval[ia[k]] = 1./luval[ia[k]];