From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 21 Dec 2023 22:42:18 +0000 (-0700)
Subject: Prohibit calling compress() on vectors with ghost elements.
X-Git-Tag: relicensing~222^2~1
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=56815c9e9151b9dbce1550c7e7e732be402140a0;p=dealii.git

Prohibit calling compress() on vectors with ghost elements.
---

diff --git a/source/lac/petsc_vector_base.cc b/source/lac/petsc_vector_base.cc
index d3db0022dd..052af43735 100644
--- a/source/lac/petsc_vector_base.cc
+++ b/source/lac/petsc_vector_base.cc
@@ -540,6 +540,13 @@ namespace PETScWrappers
   void
   VectorBase::compress(const VectorOperation::values operation)
   {
+    Assert(has_ghost_elements() == false,
+           ExcMessage("Calling compress() is only useful if a vector "
+                      "has been written into, but this is a vector with ghost "
+                      "elements and consequently is read-only. It does "
+                      "not make sense to call compress() for such "
+                      "vectors."));
+
     {
 #  ifdef DEBUG
       // Check that all processors agree that last_action is the same (or none!)
diff --git a/source/lac/trilinos_vector.cc b/source/lac/trilinos_vector.cc
index 0431f266b9..8d26487152 100644
--- a/source/lac/trilinos_vector.cc
+++ b/source/lac/trilinos_vector.cc
@@ -599,6 +599,14 @@ namespace TrilinosWrappers
     void
     Vector::compress(VectorOperation::values given_last_action)
     {
+      Assert(has_ghost_elements() == false,
+             ExcMessage(
+               "Calling compress() is only useful if a vector "
+               "has been written into, but this is a vector with ghost "
+               "elements and consequently is read-only. It does "
+               "not make sense to call compress() for such "
+               "vectors."));
+
       // Select which mode to send to Trilinos. Note that we use last_action if
       // available and ignore what the user tells us to detect wrongly mixed
       // operations. Typically given_last_action is only used on machines that