int FormJacobian_Grid(GridCtx *grid,Mat *J)
{
Mat jac = *J;
PetscErrorCode ierr;
PetscInt i,j,row,mx,my,xs,ys,xm,ym,Xs,Ys,Xm,Ym,col[5];
PetscInt nloc,*ltog,grow;
PetscScalar two = 2.0,one = 1.0,v[5],hx,hy,hxdhy,hydhx,value;
mx = grid->mx; my = grid->my;
hx = one/(PetscReal)(mx-1); hy = one/(PetscReal)(my-1);
hxdhy = hx/hy; hydhx = hy/hx;
/* Get ghost points */
ierr = DAGetCorners(grid->da,&xs,&ys,0,&xm,&ym,0);CHKERRQ(ierr);
ierr = DAGetGhostCorners(grid->da,&Xs,&Ys,0,&Xm,&Ym,0);CHKERRQ(ierr);
ierr = DAGetGlobalIndices(grid->da,&nloc,<og);CHKERRQ(ierr);
/* Evaluate Jacobian of function */
for (j=ys; j<ys+ym; j++) {
row = (j - Ys)*Xm + xs - Xs - 1;
for (i=xs; i<xs+xm; i++) {
row++;
grow = ltog[row];
if (i > 0 && i < mx-1 && j > 0 && j < my-1) {
v[0] = -hxdhy; col[0] = ltog[row - Xm];
v[1] = -hydhx; col[1] = ltog[row - 1];
v[2] = two*(hydhx + hxdhy); col[2] = grow;
v[3] = -hydhx; col[3] = ltog[row + 1];
v[4] = -hxdhy; col[4] = ltog[row + Xm];
ierr = MatSetValues(jac,1,&grow,5,col,v,INSERT_VALUES);CHKERRQ(ierr);
} else if ((i > 0 && i < mx-1) || (j > 0 && j < my-1)){
value = .5*two*(hydhx + hxdhy);
ierr = MatSetValues(jac,1,&grow,1,&grow,&value,INSERT_VALUES);CHKERRQ(ierr);
} else {
value = .25*two*(hydhx + hxdhy);
ierr = MatSetValues(jac,1,&grow,1,&grow,&value,INSERT_VALUES);CHKERRQ(ierr);
}
}
}
ierr = MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
ierr = MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
return 0;
}
#include "petscda.h"
#include "../src/sys/f90-src/f90impl.h"
#ifdef PETSC_HAVE_FORTRAN_CAPS
#define dagetglobalindicesf90_ DAGETGLOBALINDICESF90
#elif !defined(PETSC_HAVE_FORTRAN_UNDERSCORE)
#define dagetglobalindicesf90_ dagetglobalindicesf90
#endif
EXTERN_C_BEGIN
void PETSC_STDCALL dagetglobalindicesf90_(DA *da,PetscInt *n,F90Array1d *indices,int *ierr PETSC_F90_2PTR_PROTO(ptrd))
{
PetscInt *idx;
*ierr = DAGetGlobalIndices(*da,n,&idx); if (*ierr) return;
*ierr = F90Array1dCreate(idx,PETSC_INT,1,*n,indices PETSC_F90_2PTR_PARAM(ptrd));
}
EXTERN_C_END
