> > Here is the magic > PetscErrorCode VecGetArray2d(Vec x,PetscInt m,PetscInt n,PetscInt > mstart,PetscInt nstart,PetscScalar **a[]) > > ierr = VecGetLocalSize(x,&N);CHKERRQ(ierr); > if (m*n != N) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Local array > size %D does not match 2d array dimensions %D by %D",N,m,n); > ierr = VecGetArray(x,&aa);CHKERRQ(ierr); > > ierr = PetscMalloc(m*sizeof(PetscScalar*),a);CHKERRQ(ierr); > for (i=0; i<m; i++) (*a)[i] = aa + i*n - nstart; > *a -= mstart; > PetscFunctionReturn(0);
Ah, so you make a bunch of silly_1 pointers so you can index into them in a silly_2 way and silly_2 = silly_1^-1. That's easy :)
