def set_centralized_assembled_rows_cols(self, irn, jcn):
        """Set assembled matrix indices on processor 0.

        The row and column indices (irn & jcn) should be one based.
        """
        if self.myid != 0:
            return
        assert irn.size == jcn.size
        self._refs.update(irn=irn, jcn=jcn)
        self.id.nz = irn.size
        self.id.irn = self.cast_array(irn)
        self.id.jcn = self.cast_array(jcn)