YES # Parallel rule labeling (Zankl et al. 2015). Consider the left-linear TRS R: foo(0(x)) -> 0(s(p(p(p(s(s(s(p(s(x)))))))))) foo(s(x)) -> p(s(p(p(p(s(s(p(s(s(p(s(foo(p(p(s(s(p(s(bar(p(p(s(s(p(s(x)))))))))))))))))))))))))) bar(0(x)) -> 0(p(s(s(s(x))))) bar(s(x)) -> p(s(p(p(s(s(foo(s(p(p(s(s(x)))))))))))) p(p(s(x))) -> p(x) p(s(x)) -> x p(0(x)) -> 0(s(s(s(s(x))))) All parallel critical peaks (except C's) are decreasing wrt rule labeling: phi(foo(0(x)) -> 0(s(p(p(p(s(s(s(p(s(x))))))))))) = 1 phi(foo(s(x)) -> p(s(p(p(p(s(s(p(s(s(p(s(foo(p(p(s(s(p(s(bar(p(p(s(s(p(s(x))))))))))))))))))))))))))) = 1 phi(bar(0(x)) -> 0(p(s(s(s(x)))))) = 1 phi(bar(s(x)) -> p(s(p(p(s(s(foo(s(p(p(s(s(x))))))))))))) = 1 phi(p(p(s(x))) -> p(x)) = 1 phi(p(s(x)) -> x) = 1 phi(p(0(x)) -> 0(s(s(s(s(x)))))) = 1 psi(foo(0(x)) -> 0(s(p(p(p(s(s(s(p(s(x))))))))))) = 1 psi(foo(s(x)) -> p(s(p(p(p(s(s(p(s(s(p(s(foo(p(p(s(s(p(s(bar(p(p(s(s(p(s(x))))))))))))))))))))))))))) = 1 psi(bar(0(x)) -> 0(p(s(s(s(x)))))) = 1 psi(bar(s(x)) -> p(s(p(p(s(s(foo(s(p(p(s(s(x))))))))))))) = 1 psi(p(p(s(x))) -> p(x)) = 1 psi(p(s(x)) -> x) = 1 psi(p(0(x)) -> 0(s(s(s(s(x)))))) = 1