Date: 2026-06-01T23:13:54+00:00

Actual source code: ex5.c

      1: static char help[] = "Tests binary I/O of vectors and illustrates the use of user-defined event logging.\n\n";

      3: #include <petscvec.h>

      5: /* Note:  Most applications would not read and write a vector within
      6:   the same program.  This example is intended only to demonstrate
      7:   both input and output. */

      9: int main(int argc, char **args)
     10: {
     11:   PetscMPIInt   rank, size;
     12:   PetscInt      i, m = 10, low, high, ldim, iglobal;
     13:   PetscScalar   v;
     14:   Vec           u;
     15:   PetscViewer   viewer;
     16:   PetscLogEvent VECTOR_GENERATE, VECTOR_READ;

     18:   PetscFunctionBeginUser;
     19:   PetscCall(PetscInitialize(&argc, &args, NULL, help));
     20:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
     21:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
     22:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));

     24:   /* PART 1:  Generate vector, then write it in binary format */

     26:   PetscCall(PetscLogEventRegister("Generate Vector", VEC_CLASSID, &VECTOR_GENERATE));
     27:   PetscCall(PetscLogEventBegin(VECTOR_GENERATE, 0, 0, 0, 0));
     28:   /* Generate vector */
     29:   PetscCall(VecCreate(PETSC_COMM_WORLD, &u));
     30:   PetscCall(VecSetSizes(u, PETSC_DECIDE, m));
     31:   PetscCall(VecSetFromOptions(u));
     32:   PetscCall(VecGetOwnershipRange(u, &low, &high));
     33:   PetscCall(VecGetLocalSize(u, &ldim));
     34:   for (i = 0; i < ldim; i++) {
     35:     iglobal = i + low;
     36:     v       = (PetscScalar)(i + 100 * rank);
     37:     PetscCall(VecSetValues(u, 1, &iglobal, &v, INSERT_VALUES));
     38:   }
     39:   PetscCall(VecAssemblyBegin(u));
     40:   PetscCall(VecAssemblyEnd(u));
     41:   PetscCall(VecView(u, PETSC_VIEWER_STDOUT_WORLD));

     43:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "writing vector in binary to vector.dat ...\n"));
     44:   PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, "vector.dat", FILE_MODE_WRITE, &viewer));
     45:   PetscCall(VecView(u, viewer));
     46:   PetscCall(PetscViewerDestroy(&viewer));
     47:   PetscCall(VecDestroy(&u));
     48:   PetscCall(PetscOptionsSetValue(NULL, "-viewer_binary_mpiio", ""));

     50:   PetscCall(PetscLogEventEnd(VECTOR_GENERATE, 0, 0, 0, 0));

     52:   /* PART 2:  Read in vector in binary format */

     54:   /* Read new vector in binary format */
     55:   PetscCall(PetscLogEventRegister("Read Vector", VEC_CLASSID, &VECTOR_READ));
     56:   PetscCall(PetscLogEventBegin(VECTOR_READ, 0, 0, 0, 0));
     57:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "reading vector in binary from vector.dat ...\n"));
     58:   PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, "vector.dat", FILE_MODE_READ, &viewer));
     59:   PetscCall(VecCreate(PETSC_COMM_WORLD, &u));
     60:   PetscCall(VecLoad(u, viewer));
     61:   PetscCall(PetscViewerDestroy(&viewer));
     62:   PetscCall(PetscLogEventEnd(VECTOR_READ, 0, 0, 0, 0));
     63:   PetscCall(VecView(u, PETSC_VIEWER_STDOUT_WORLD));

     65:   /* Free data structures */
     66:   PetscCall(VecDestroy(&u));
     67:   PetscCall(PetscFinalize());
     68:   return 0;
     69: }

     71: /*TEST

     73:      test:
     74:        nsize: 1
     75:        requires: mpiio

     77:      test:
     78:        suffix: 2
     79:        nsize: 2
     80:        requires: mpiio

     82: TEST*/