Actual source code: ex18.c

  1: static char help[] = "Reads a PETSc matrix and vector from a file and solves a linear system.\n\
  2: Input arguments are:\n\
  3:   -f <input_file> : file to load.  For example see $PETSC_DIR/share/petsc/datafiles/matrices\n\n";

  5: #include <petscmat.h>
  6: #include <petscksp.h>

  8: int main(int argc, char **args)
  9: {
 10:   PetscInt      its, m, n, mvec;
 11:   PetscReal     norm;
 12:   Vec           x, b, u;
 13:   Mat           A;
 14:   KSP           ksp;
 15:   char          file[PETSC_MAX_PATH_LEN];
 16:   PetscViewer   fd;
 17:   PetscLogStage stage1;

 19:   PetscFunctionBeginUser;
 20:   PetscCall(PetscInitialize(&argc, &args, NULL, help));

 22:   /* Read matrix and RHS */
 23:   PetscCall(PetscOptionsGetString(NULL, NULL, "-f", file, sizeof(file), NULL));
 24:   PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file, FILE_MODE_READ, &fd));
 25:   PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
 26:   PetscCall(MatSetType(A, MATSEQAIJ));
 27:   PetscCall(MatLoad(A, fd));
 28:   PetscCall(VecCreate(PETSC_COMM_WORLD, &b));
 29:   PetscCall(VecLoad(b, fd));
 30:   PetscCall(PetscViewerDestroy(&fd));

 32:   /*
 33:      If the load matrix is larger then the vector, due to being padded
 34:      to match the blocksize then create a new padded vector
 35:   */
 36:   PetscCall(MatGetSize(A, &m, &n));
 37:   PetscCall(VecGetSize(b, &mvec));
 38:   if (m > mvec) {
 39:     Vec          tmp;
 40:     PetscScalar *bold, *bnew;
 41:     /* create a new vector b by padding the old one */
 42:     PetscCall(VecCreate(PETSC_COMM_WORLD, &tmp));
 43:     PetscCall(VecSetSizes(tmp, PETSC_DECIDE, m));
 44:     PetscCall(VecSetFromOptions(tmp));
 45:     PetscCall(VecGetArray(tmp, &bnew));
 46:     PetscCall(VecGetArray(b, &bold));
 47:     PetscCall(PetscArraycpy(bnew, bold, mvec));
 48:     PetscCall(VecDestroy(&b));
 49:     b = tmp;
 50:   }

 52:   /* Set up solution */
 53:   PetscCall(VecDuplicate(b, &x));
 54:   PetscCall(VecDuplicate(b, &u));
 55:   PetscCall(VecSet(x, 0.0));

 57:   /* Solve system */
 58:   PetscCall(PetscLogStageRegister("Stage 1", &stage1));
 59:   PetscCall(PetscLogStagePush(stage1));
 60:   PetscCall(KSPCreate(PETSC_COMM_WORLD, &ksp));
 61:   PetscCall(KSPSetOperators(ksp, A, A));
 62:   PetscCall(KSPSetFromOptions(ksp));
 63:   PetscCall(KSPSolve(ksp, b, x));
 64:   PetscCall(PetscLogStagePop());

 66:   /* Show result */
 67:   PetscCall(MatMult(A, x, u));
 68:   PetscCall(VecAXPY(u, -1.0, b));
 69:   PetscCall(VecNorm(u, NORM_2, &norm));
 70:   PetscCall(KSPGetIterationNumber(ksp, &its));
 71:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Number of iterations = %3" PetscInt_FMT "\n", its));
 72:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Residual norm %g\n", (double)norm));

 74:   /* Cleanup */
 75:   PetscCall(KSPDestroy(&ksp));
 76:   PetscCall(VecDestroy(&x));
 77:   PetscCall(VecDestroy(&b));
 78:   PetscCall(VecDestroy(&u));
 79:   PetscCall(MatDestroy(&A));

 81:   PetscCall(PetscFinalize());
 82:   return 0;
 83: }

 85: /*TEST

 87:     test:
 88:       args: -ksp_gmres_cgs_refinement_type refine_always -f ${DATAFILESPATH}/matrices/arco1 -ksp_monitor_short
 89:       requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)

 91: TEST*/