From: Wolfgang Bangerth Date: Mon, 6 Jan 2020 19:48:49 +0000 (-0700) Subject: Augment the UMFPACK error message. X-Git-Tag: v9.2.0-rc1~722^2 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F9235%2Fhead;p=dealii.git Augment the UMFPACK error message. --- diff --git a/include/deal.II/lac/sparse_direct.h b/include/deal.II/lac/sparse_direct.h index a354636531..ee20a40124 100644 --- a/include/deal.II/lac/sparse_direct.h +++ b/include/deal.II/lac/sparse_direct.h @@ -304,9 +304,12 @@ public: "want to check your assembly procedure. Similarly, a " "matrix can be rank deficient if you forgot to apply the " "appropriate boundary conditions. For example, the " - "Laplace equation without boundary conditions has a " - "single zero eigenvalue and its rank is therefore " - "deficient by one." + "Laplace equation for a problem where only Neumann boundary " + "conditions are posed (or where you forget to apply Dirichlet " + "boundary conditions) has exactly one eigenvalue equal to zero " + "and its rank is therefore deficient by one. Finally, the matrix " + "may be rank deficient because you are using a quadrature " + "formula with too few quadrature points." "\n\n" "The other common situation is that you run out of memory. " "On a typical laptop or desktop, it should easily be possible "