Actual source code: ex18.c


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

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

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

 23:   PetscInitialize(&argc, &args, (char *)0, help);

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

 35:   /*
 36:      If the load matrix is larger then the vector, due to being padded
 37:      to match the blocksize then create a new padded vector
 38:   */
 39:   MatGetSize(A, &m, &n);
 40:   VecGetSize(b, &mvec);
 41:   if (m > mvec) {
 42:     Vec          tmp;
 43:     PetscScalar *bold, *bnew;
 44:     /* create a new vector b by padding the old one */
 45:     VecCreate(PETSC_COMM_WORLD, &tmp);
 46:     VecSetSizes(tmp, PETSC_DECIDE, m);
 47:     VecSetFromOptions(tmp);
 48:     VecGetArray(tmp, &bnew);
 49:     VecGetArray(b, &bold);
 50:     PetscArraycpy(bnew, bold, mvec);
 51:     VecDestroy(&b);
 52:     b = tmp;
 53:   }

 55:   /* Set up solution */
 56:   VecDuplicate(b, &x);
 57:   VecDuplicate(b, &u);
 58:   VecSet(x, 0.0);

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

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

 77:   /* Cleanup */
 78:   KSPDestroy(&ksp);
 79:   VecDestroy(&x);
 80:   VecDestroy(&b);
 81:   VecDestroy(&u);
 82:   MatDestroy(&A);

 84:   PetscFinalize();
 85:   return 0;
 86: }

 88: /*TEST

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

 94: TEST*/