1 2 static char help[] = "Demonstrates calling Trilinos and then PETSc in the same program.\n\n"; 3 4 /*T 5 Concepts: introduction to PETSc^Trilinos 6 Processors: n 7 8 Example obtained from: http://trilinos.org/docs/dev/packages/tpetra/doc/html/Tpetra_Lesson01.html 9 T*/ 10 11 #include <petscsys.h> 12 #include <Tpetra_DefaultPlatform.hpp> 13 #include <Tpetra_Version.hpp> 14 #include <Teuchos_GlobalMPISession.hpp> // used if Trilinos is the one that starts up MPI 15 16 // Do something with the given communicator. In this case, we just 17 // print Tpetra's version to stdout on Process 0 in the given 18 // communicator. 19 void 20 exampleRoutine (const Teuchos::RCP<const Teuchos::Comm<int> >& comm) 21 { 22 if (comm->getRank () == 0) { 23 // On (MPI) Process 0, print out the Tpetra software version. 24 std::cout << Tpetra::version () << std::endl << std::endl; 25 } 26 } 27 28 int main(int argc,char **argv) 29 { 30 // These "using" declarations make the code more concise, in that 31 // you don't have to write the namespace along with the class or 32 // object name. This is especially helpful with commonly used 33 // things like std::endl. 34 using std::cout; 35 using std::endl; 36 // Start up MPI, if using MPI. Trilinos doesn't have to be built 37 // with MPI; it's called a "serial" build if you build without MPI. 38 // GlobalMPISession hides this implementation detail. 39 // 40 // Note the third argument. If you pass GlobalMPISession the 41 // address of an std::ostream, it will print a one-line status 42 // message with the rank on each MPI process. This may be 43 // undesirable if running with a large number of MPI processes. 44 // You can avoid printing anything here by passing in either 45 // NULL or the address of a Teuchos::oblackholestream. 46 Teuchos::GlobalMPISession mpiSession (&argc, &argv, NULL); 47 // Get a pointer to the communicator object representing 48 // MPI_COMM_WORLD. getDefaultPlatform.getComm() doesn't create a 49 // new object every time you call it; it just returns the same 50 // communicator each time. Thus, you can call it anywhere and get 51 // the same communicator. (This is handy if you don't want to pass 52 // a communicator around everywhere, though it's always better to 53 // parameterize your algorithms on the communicator.) 54 // 55 // "Tpetra::DefaultPlatform" knows whether or not we built with MPI 56 // support. If we didn't build with MPI, we'll get a "communicator" 57 // with size 1, whose only process has rank 0. 58 Teuchos::RCP<const Teuchos::Comm<int> > comm = Tpetra::DefaultPlatform::getDefaultPlatform ().getComm (); 59 60 PetscCall(PetscInitialize(&argc,&argv,(char*)0,help)); 61 62 // Get my process' rank, and the total number of processes. 63 // Equivalent to MPI_Comm_rank resp. MPI_Comm_size. 64 const int myRank = comm->getRank (); 65 const int size = comm->getSize (); 66 if (myRank == 0) { 67 cout << "Total number of processes: " << size << endl; 68 } 69 // Do something with the new communicator. 70 exampleRoutine (comm); 71 // This tells the Trilinos test framework that the test passed. 72 if (myRank == 0) { 73 cout << "End Result: TEST PASSED" << endl; 74 } 75 // GlobalMPISession calls MPI_Finalize() in its destructor, if 76 // appropriate. You don't have to do anything here! Just return 77 // from main(). Isn't that helpful? 78 PetscCall(PetscFinalize()); 79 return 0; 80 } 81 82 /*TEST 83 84 build: 85 requires: trilinos 86 87 test: 88 nsize: 3 89 filter: grep -v "Tpetra in Trilinos" 90 91 TEST*/ 92