From: Toby D. Young <tyoung@ippt.pan.pl>
Date: Wed, 21 Aug 2013 10:39:34 +0000 (+0000)
Subject: Can not compute residual norms if no eigenvectors have converged.
X-Git-Tag: v8.1.0~1026
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=426489da7cf5de0ff2875a01d188bf8c15e41aca;p=dealii.git

Can not compute residual norms if no eigenvectors have converged.

git-svn-id: https://svn.dealii.org/trunk@30369 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/source/lac/slepc_solver.cc b/deal.II/source/lac/slepc_solver.cc
index 4c2576646d..fe91deb0b0 100644
--- a/deal.II/source/lac/slepc_solver.cc
+++ b/deal.II/source/lac/slepc_solver.cc
@@ -187,11 +187,11 @@ namespace SLEPcWrappers
 
     // get number of converged eigenstates
     ierr = EPSGetConverged (solver_data->eps,
-                            reinterpret_cast<PetscInt *>(n_converged));
+                            reinterpret_cast<PetscInt*>(n_converged));
     AssertThrow (ierr == 0, ExcSLEPcError(ierr));
 
-    PetscInt n_iterations = 0;
-    double residual_norm = 1e300;
+    PetscInt n_iterations   = 0;
+    PetscReal residual_norm = 1.e300;
 
     // @todo Investigate elaborating on some of this to act on the
     // complete eigenspectrum
@@ -200,9 +200,13 @@ namespace SLEPcWrappers
       ierr = EPSGetIterationNumber (solver_data->eps, &n_iterations);
       AssertThrow (ierr == 0, ExcSLEPcError(ierr));
 
-      // get the residual norm of the most extreme eigenvalue
-      ierr = EPSComputeResidualNorm (solver_data->eps, 0, &residual_norm);
-      AssertThrow (ierr == 0, ExcSLEPcError(ierr));
+      // get the residual norm of the most extreme eigenvalue if and
+      // only if at least one eigenvector has converged.
+      if ((*n_converged)>0)
+	{
+	  ierr = EPSComputeResidualNorm (solver_data->eps, 0, &residual_norm);
+	  AssertThrow (ierr == 0, ExcSLEPcError(ierr));
+	}
 
       // check the solver state
       const SolverControl::State state