YES # Parallel rule labeling (Zankl et al. 2015). Consider the left-linear TRS R: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) dbl(x) -> +(x,x) +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) All parallel critical peaks (except C's) are decreasing wrt rule labeling: phi(+(x,0()) -> x) = 4 phi(+(x,s(y)) -> s(+(x,y))) = 4 phi(+(0(),y) -> y) = 4 phi(+(s(x),y) -> s(+(x,y))) = 4 phi(dbl(x) -> +(x,x)) = 1 phi(+(+(x,y),z) -> +(x,+(y,z))) = 6 phi(+(x,y) -> +(y,x)) = 3 psi(+(x,0()) -> x) = 2 psi(+(x,s(y)) -> s(+(x,y))) = 7 psi(+(0(),y) -> y) = 4 psi(+(s(x),y) -> s(+(x,y))) = 2 psi(dbl(x) -> +(x,x)) = 1 psi(+(+(x,y),z) -> +(x,+(y,z))) = 5 psi(+(x,y) -> +(y,x)) = 1