> On Sep 4, 2017, at 4:09 PM, zakaryah . <[email protected]> wrote: > > OK that is super helpful. Just to be sure - for MxNxP, the row r in the > Jacobian is at r.i*P*N*3 + r.j*P*3 + r.k*3 + r.c?
It is that way, or the other way around r.k*M*N*3 + r.j*N*3 + r.k*3 + r.c > > > On Mon, Sep 4, 2017 at 4:58 PM, Barry Smith <[email protected]> wrote: > > > On Sep 4, 2017, at 3:48 PM, zakaryah . <[email protected]> wrote: > > > > One piece of information that would be useful is what ordering PETSc uses > > for the Jacobian in the snes_test_display. Is it a natural ordering, or > > the PETSc ordering? For debugging the Jacobian manually, the natural > > ordering is much easier to work with. > > What is displayed is always the natural ordering (internally it is not the > natural ordering). > > > For -n 1, are the orderings the same? > > yes > > > > > > > If I use a MatStencil r to represent a field with 3 degrees of freedom, and > > the dimensions of my 3D DMDA are MxNxP, which row of the Jacobian > > corresponds to r.i=x, r.j=y, r.k=z, r.c=f? > > Internally it is complicated but for any viewing it is just the natural > ordering and all the degrees of freedom for a single point are next to each > other in the vector/matrix. > >
