As per https://gitlab.com/petsc/petsc/-/issues/852 we have some fairly complex functions in MOOSE that sometimes require the matrix to be "assembled" at an intermediate stage of our Jacobian evaluation in order to perform multi-body Constraints. In an ideal world I would like to assemble with FLUSH because as per my post today in petsc-users FINAL may shrink my allocation before I'm ready for it to.
We cannot currently use FLUSH at intermediate stages, however, because there is a late call to MatZeroRows which we leverage before applying our last set of objects (which are Dirichlet boundary conditions). MatZeroRows checks the `assembled` flag which only gets set during FINAL assembly and errors out if `assembled` is not true. From my understanding, MatZeroRows should be a safe operation even if the matrix has just been FLUSHed. MatZeroRows is just one example; I would guess there are other operations that could potentially be done with a FLUSHed matrix as opposed to a fully assembled one. Consequently, I'm wondering if it makes sense to add something like a `flushed` data member to _p_Mat that would allow for some less strict checking in operations like MatZeroRows. Alex
