Update a comment that is no longer accurate.

git-svn-id: https://svn.dealii.org/trunk@24424 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/examples/step-31/step-31.cc b/deal.II/examples/step-31/step-31.cc
index 6be583c6de3689440c50e619259c3fdd907bd148..50136034278f528a5630ef2a0a96fd15d1fd7487 100644 (file)
--- a/deal.II/examples/step-31/step-31.cc
+++ b/deal.II/examples/step-31/step-31.cc
@@ -2880,14 +2880,25 @@ namespace Step31
                                 // @sect3{The <code>main</code> function}
                                 //
                                 // The main function looks almost the same
-                                // as in all other programs. The only
-                                // difference is that Trilinos wants to get
-                                // the arguments from calling the function
-                                // (argc and argv) in order to correctly
-                                // set up the MPI system in case those
-                                // compilers are in use (even though this
-                                // program is only meant to be run on one
-                                // processor).
+                                // as in all other programs.
+                                //
+                                // There is one difference we have to be
+                                // careful about. This program uses Trilinos
+                                // and, typically, Trilinos is configured so
+                                // that it can run in %parallel using
+                                // MPI. This doesn't mean that it <i>has</i>
+                                // to run in %parallel, and in fact this
+                                // program (unlike step-32) makes no attempt
+                                // at all to do anything in %parallel using
+                                // MPI. Nevertheless, Trilinos wants the MPI
+                                // system to be initialized. We do that be
+                                // creating an object of type
+                                // Utilities::System::MPI_InitFinalize that
+                                // initializes MPI (if available) using the
+                                // arguments given to main() (i.e.,
+                                // <code>argc</code> and <code>argv</code>)
+                                // and de-initializes it again when the
+                                // object goes out of scope.
 int main (int argc, char *argv[])
 {
   try