From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Tue, 15 Feb 2022 03:40:58 +0000 (-0700)
Subject: Improve an error message.
X-Git-Tag: v9.4.0-rc1~494^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=42b0cd61e37d659cef39eb2303d406be5c86e245;p=dealii.git

Improve an error message.
---

diff --git a/include/deal.II/lac/petsc_vector_base.h b/include/deal.II/lac/petsc_vector_base.h
index cdc19ab169..b253095eb3 100644
--- a/include/deal.II/lac/petsc_vector_base.h
+++ b/include/deal.II/lac/petsc_vector_base.h
@@ -1254,7 +1254,14 @@ namespace PETScWrappers
 
             Assert(index >= static_cast<unsigned int>(begin) &&
                      index < static_cast<unsigned int>(end),
-                   ExcInternalError());
+                   ExcMessage("You are accessing elements of a vector without "
+                              "ghost elements that are not actually owned by "
+                              "this vector. A typical case where this may "
+                              "happen is if you are passing a non-ghosted "
+                              "(completely distributed) vector to a function "
+                              "that expects a vector that stores ghost "
+                              "elements for all locally relevant or locally "
+                              "active vector entries."));
 
             *(values_begin + i) = *(ptr + index - begin);
           }