From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Fri, 25 Feb 2022 21:31:08 +0000 (-0700)
Subject: Provide a second error for Trilinos sparsity pattern problems.
X-Git-Tag: v9.4.0-rc1~427^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F13452%2Fhead;p=dealii.git

Provide a second error for Trilinos sparsity pattern problems.
---

diff --git a/source/lac/trilinos_sparsity_pattern.cc b/source/lac/trilinos_sparsity_pattern.cc
index 71111b2b6e..692c623d7b 100644
--- a/source/lac/trilinos_sparsity_pattern.cc
+++ b/source/lac/trilinos_sparsity_pattern.cc
@@ -710,7 +710,25 @@ namespace TrilinosWrappers
         AssertThrow(ierr == 0, ExcTrilinosError(ierr));
       }
 
-    ierr = graph->OptimizeStorage();
+    try
+      {
+        ierr = graph->OptimizeStorage();
+      }
+    catch (const int error_code)
+      {
+        AssertThrow(
+          false,
+          ExcMessage(
+            "The Epetra_CrsGraph::OptimizeStorage() function "
+            "has thrown an error with code " +
+            std::to_string(error_code) +
+            ". You will have to look up the exact meaning of this error "
+            "in the Trilinos source code, but oftentimes, this function "
+            "throwing an error indicates that you are trying to allocate "
+            "more than 2,147,483,647 nonzero entries in the sparsity "
+            "pattern on the local process; this will not work because "
+            "Epetra indexes entries with a simple 'signed int'."));
+      }
     AssertThrow(ierr == 0, ExcTrilinosError(ierr));
   }