Actual source code: ex46.cxx


  2: static char help[] = "Demonstrates calling Trilinos and then PETSc in the same program.\n\n";

  4: /*
  5:    Example obtained from: http://trilinos.org/docs/dev/packages/tpetra/doc/html/Tpetra_Lesson01.html
  6: */

  8: #include <petscsys.h>
  9: #include <Tpetra_DefaultPlatform.hpp>
 10: #include <Tpetra_Version.hpp>
 11: #include <Teuchos_GlobalMPISession.hpp> // used if Trilinos is the one that starts up MPI

 13: // Do something with the given communicator.  In this case, we just
 14: // print Tpetra's version to stdout on Process 0 in the given
 15: // communicator.
 16: void exampleRoutine(const Teuchos::RCP<const Teuchos::Comm<int>> &comm)
 17: {
 18:   if (comm->getRank() == 0) {
 19:     // On (MPI) Process 0, print out the Tpetra software version.
 20:     std::cout << Tpetra::version() << std::endl << std::endl;
 21:   }
 22: }

 24: int main(int argc, char **argv)
 25: {
 26:   // These "using" declarations make the code more concise, in that
 27:   // you don't have to write the namespace along with the class or
 28:   // object name.  This is especially helpful with commonly used
 29:   // things like std::endl.
 30:   using std::cout;
 31:   using std::endl;
 32:   // Start up MPI, if using MPI.  Trilinos doesn't have to be built
 33:   // with MPI; it's called a "serial" build if you build without MPI.
 34:   // GlobalMPISession hides this implementation detail.
 35:   //
 36:   // Note the third argument.  If you pass GlobalMPISession the
 37:   // address of an std::ostream, it will print a one-line status
 38:   // message with the rank on each MPI process.  This may be
 39:   // undesirable if running with a large number of MPI ranks.
 40:   // You can avoid printing anything here by passing in either
 41:   // NULL or the address of a Teuchos::oblackholestream.
 42:   Teuchos::GlobalMPISession mpiSession(&argc, &argv, NULL);
 43:   // Get a pointer to the communicator object representing
 44:   // MPI_COMM_WORLD.  getDefaultPlatform.getComm() doesn't create a
 45:   // new object every time you call it; it just returns the same
 46:   // communicator each time.  Thus, you can call it anywhere and get
 47:   // the same communicator.  (This is handy if you don't want to pass
 48:   // a communicator around everywhere, though it's always better to
 49:   // parameterize your algorithms on the communicator.)
 50:   //
 51:   // "Tpetra::DefaultPlatform" knows whether or not we built with MPI
 52:   // support.  If we didn't build with MPI, we'll get a "communicator"
 53:   // with size 1, whose only process has rank 0.
 54:   Teuchos::RCP<const Teuchos::Comm<int>> comm = Tpetra::DefaultPlatform::getDefaultPlatform().getComm();

 56:   PetscFunctionBeginUser;
 57:   PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));

 59:   // Get my process' rank, and the total number of processes.
 60:   // Equivalent to MPI_Comm_rank resp. MPI_Comm_size.
 61:   const int myRank = comm->getRank();
 62:   const int size   = comm->getSize();
 63:   if (myRank == 0) cout << "Total number of processes: " << size << endl;
 64:   // Do something with the new communicator.
 65:   exampleRoutine(comm);
 66:   // This tells the Trilinos test framework that the test passed.
 67:   if (myRank == 0) cout << "End Result: TEST PASSED" << endl;
 68:   // GlobalMPISession calls MPI_Finalize() in its destructor, if
 69:   // appropriate.  You don't have to do anything here!  Just return
 70:   // from main().  Isn't that helpful?
 71:   PetscCall(PetscFinalize());
 72:   return 0;
 73: }

 75: /*TEST

 77:    build:
 78:      requires: trilinos

 80:    test:
 81:       nsize: 3
 82:       filter: grep -v "Tpetra in Trilinos"

 84: TEST*/