Tpetra_Util.cpp

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//          Tpetra: Templated Linear Algebra Services Package
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#include <Tpetra_Util.hpp>

namespace Tpetra {
namespace Details {

bool
congruent (const Teuchos::Comm<int>& comm1,
           const Teuchos::Comm<int>& comm2)
{
#ifdef HAVE_MPI
  using Teuchos::Comm;
  using Teuchos::RCP;
  using Teuchos::rcpFromRef;
  using Teuchos::MpiComm;
  using Teuchos::rcp_dynamic_cast;

  RCP<const MpiComm<int> > mpiComm1 =
    rcp_dynamic_cast<const MpiComm<int> > (rcpFromRef (comm1));
  RCP<const MpiComm<int> > mpiComm2 =
    rcp_dynamic_cast<const MpiComm<int> > (rcpFromRef (comm2));

  if (mpiComm1.is_null ()) { // comm1 is not an MpiComm
    return comm1.getSize () == comm2.getSize (); // hope for the best
  } else { // comm1 is an MpiComm
    if (mpiComm2.is_null ()) { // comm2 is not an MpiComm
      return comm1.getSize () == comm2.getSize (); // hope for the best
    } else { // both comm1 and comm2 are MpiComm
      MPI_Comm rawMpiComm1 = * (mpiComm1->getRawMpiComm ());
      MPI_Comm rawMpiComm2 = * (mpiComm2->getRawMpiComm ());

      int result = MPI_UNEQUAL;
      const int err = MPI_Comm_compare (rawMpiComm1, rawMpiComm2, &result);
      TEUCHOS_TEST_FOR_EXCEPTION(err != MPI_SUCCESS, std::runtime_error,
                                 "congruent: MPI_Comm_compare failed");
      return result == MPI_IDENT || result == MPI_CONGRUENT;
    }
  }
#else // NOT HAVE_MPI
  return comm1.getSize () == comm2.getSize (); // hope for the best
#endif // HAVE_MPI
}

} // namespace Details
} // namespace Tpetra