50   UserContext ctxt;  in main()  local
56   ctxt.a            = 0.1;  in main()
57   ctxt.xmin         = 0.0;  in main()
58   ctxt.xmax         = 1.0;  in main()
59   ctxt.imax         = 40;  in main()
60   ctxt.physics_type = PHYSICS_DIFFUSION;  in main()
63   PetscCall(PetscOptionsReal("-a", "diffusion coefficient", "<1.0>", ctxt.a, &ctxt.a, NULL));  in main()
64   PetscCall(PetscOptionsInt("-imax", "grid size", "<20>", ctxt.imax, &ctxt.imax, NULL));  in main()
65   PetscCall(PetscOptionsReal("-xmin", "xmin", "<0.0>", ctxt.xmin, &ctxt.xmin, NULL));  in main()
66   PetscCall(PetscOptionsReal("-xmax", "xmax", "<1.0>", ctxt.xmax, &ctxt.xmax, NULL));  in main()
67 …e of process to discretize", "", PhysicsTypes, (PetscEnum)ctxt.physics_type, (PetscEnum *)&ctxt.ph…  in main()
72   PetscCall(VecSetSizes(u, PETSC_DECIDE, ctxt.imax));  in main()
76   PetscCall(ExactSolution(u, &ctxt, 0.0));  in main()
80   PetscCall(MatSetSizes(A, PETSC_DECIDE, PETSC_DECIDE, ctxt.imax, ctxt.imax));  in main()
91   PetscCall(TSSetRHSFunction(ts, NULL, TSComputeRHSFunctionLinear, &ctxt));  in main()
92   PetscCall(RHSJacobian(ts, 0, u, A, A, &ctxt));  in main()
93   PetscCall(TSSetRHSJacobian(ts, A, A, TSComputeRHSJacobianConstant, &ctxt));  in main()
99   PetscCall(ExactSolution(uex, &ctxt, ftime));  in main()
104   err = PetscSqrtReal(err * err / ((PetscReal)ctxt.imax));  in main()
118   UserContext *ctxt = (UserContext *)c;  in ExactSolution()  local
121   PetscReal    x, dx, a = ctxt->a, pi = PETSC_PI;  in ExactSolution()
124   dx = (ctxt->xmax - ctxt->xmin) / ((PetscReal)ctxt->imax);  in ExactSolution()
129     switch (ctxt->physics_type) {  in ExactSolution()
137 …SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "No support for physics type %s", PhysicsTypes[ctxt->physi…  in ExactSolution()