1! 2! Demonstrates use of DMDASNESSetFunctionLocal() from Fortran 3! 4! Note: the access to the entries of the local arrays below use the Fortran 5! convention of starting at zero. However calls to MatSetValues() start at 0. 6! Also note that you will have to map the i,j,k coordinates to the local PETSc ordering 7! before calling MatSetValuesLocal(). Often you will find that using PETSc's default 8! code for computing the Jacobian works fine and you will not need to implement 9! your own FormJacobianLocal(). 10 11program ex40f90 12#include <petsc/finclude/petscsnes.h> 13#include <petsc/finclude/petscdmda.h> 14 use petscdmda 15 use petscsnes 16 implicit none 17 18 SNES snes 19 PetscErrorCode ierr 20 DM da 21 PetscInt ten, two, one 22 PetscScalar sone 23 Vec x 24 external FormFunctionLocal 25 26 PetscCallA(PetscInitialize(ierr)) 27 ten = 10 28 one = 1 29 two = 2 30 sone = 1.0 31 32 PetscCallA(DMDACreate2d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, DMDA_STENCIL_BOX, ten, ten, PETSC_DECIDE, PETSC_DECIDE, two, one, PETSC_NULL_INTEGER_ARRAY, PETSC_NULL_INTEGER_ARRAY, da, ierr)) 33 PetscCallA(DMSetFromOptions(da, ierr)) 34 PetscCallA(DMSetUp(da, ierr)) 35 36! Create solver object and associate it with the unknowns (on the grid) 37 38 PetscCallA(SNESCreate(PETSC_COMM_WORLD, snes, ierr)) 39 PetscCallA(SNESSetDM(snes, da, ierr)) 40 41 PetscCallA(DMDASNESSetFunctionLocal(da, INSERT_VALUES, FormFunctionLocal, 0, ierr)) 42 PetscCallA(SNESSetFromOptions(snes, ierr)) 43 44! Solve the nonlinear system 45! 46 PetscCallA(DMCreateGlobalVector(da, x, ierr)) 47 PetscCallA(VecSet(x, sone, ierr)) 48 PetscCallA(SNESSolve(snes, PETSC_NULL_VEC, x, ierr)) 49 50 PetscCallA(VecDestroy(x, ierr)) 51 PetscCallA(SNESDestroy(snes, ierr)) 52 PetscCallA(DMDestroy(da, ierr)) 53 PetscCallA(PetscFinalize(ierr)) 54end 55 56subroutine FormFunctionLocal(in, x, f, dummy, ierr) 57 use petscdmda 58 implicit none 59 PetscInt i, j, k, dummy 60 DMDALocalInfo in 61 PetscScalar x(in%DOF, in%GXS + 1:in%GXS + in%GXM, in%GYS + 1:in%GYS + in%GYM) 62 PetscScalar f(in%DOF, in%XS + 1:in%XS + in%XM, in%YS + 1:in%YS + in%YM) 63 PetscErrorCode ierr 64 65 do i = in%XS + 1, in%XS + in%XM 66 do j = in%YS + 1, in%YS + in%YM 67 do k = 1, in%DOF 68 f(k, i, j) = x(k, i, j)*x(k, i, j) - 2.0 69 end do 70 end do 71 end do 72 73end 74 75!/*TEST 76! 77! test: 78! args: -snes_monitor_short -snes_view -da_refine 1 -pc_type mg -pc_mg_type full -ksp_type fgmres -pc_mg_galerkin pmat 79! requires: !single 80! 81!TEST*/ 82