def iteration_stats(self, k, r, s, epri, edua):
        """Construct iteration stats record tuple."""

        tk = self.timer.elapsed(self.opt['IterTimer'])
        tpl = (k,) + self.eval_objfn() + (r, s, epri, edua, self.rho) + \
            self.itstat_extra() + (tk,)
        return type(self).IterationStats(*tpl)
Construct iteration stats record tuple.