YES # Parallel rule labeling (Zankl et al. 2015). Consider the left-linear TRS R: +(x,+(y,z)) -> +(+(x,y),z) +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) +(s(x),y) -> +(x,s(y)) +(x,s(y)) -> +(s(x),y) *(x,s(y)) -> +(x,*(x,y)) *(s(x),y) -> +(*(x,y),y) *(x,y) -> *(y,x) sq(x) -> *(x,x) sq(s(x)) -> +(*(x,x),s(+(x,x))) All parallel critical peaks (except C's) are decreasing wrt rule labeling: phi(+(x,+(y,z)) -> +(+(x,y),z)) = 6 phi(+(+(x,y),z) -> +(x,+(y,z))) = 7 phi(+(x,y) -> +(y,x)) = 2 phi(+(s(x),y) -> +(x,s(y))) = 1 phi(+(x,s(y)) -> +(s(x),y)) = 10 phi(*(x,s(y)) -> +(x,*(x,y))) = 11 phi(*(s(x),y) -> +(*(x,y),y)) = 12 phi(*(x,y) -> *(y,x)) = 14 phi(sq(x) -> *(x,x)) = 17 phi(sq(s(x)) -> +(*(x,x),s(+(x,x)))) = 15 psi(+(x,+(y,z)) -> +(+(x,y),z)) = 9 psi(+(+(x,y),z) -> +(x,+(y,z))) = 8 psi(+(x,y) -> +(y,x)) = 5 psi(+(s(x),y) -> +(x,s(y))) = 4 psi(+(x,s(y)) -> +(s(x),y)) = 3 psi(*(x,s(y)) -> +(x,*(x,y))) = 16 psi(*(s(x),y) -> +(*(x,y),y)) = 15 psi(*(x,y) -> *(y,x)) = 13 psi(sq(x) -> *(x,x)) = 15 psi(sq(s(x)) -> +(*(x,x),s(+(x,x)))) = 17