@utils.cached_property
    def layout_vec(self):
        vec = PETSc.Vec().create()
        # Size of flattened vector is product of size and cdim of each dat
        size = sum(d.size * d.cdim for d in self)
        vec.setSizes((size, None))
        vec.setUp()
        return vec
A PETSc Vec compatible with the dof layout of this MixedDataSet.
dataset/ETHPy150Open OP2/PyOP2/pyop2/petsc_base.py/MixedDataSet.layout_vec