YES Problem: f(s(x),y) -> f(x,s(x)) f(x,s(y)) -> f(y,x) Proof: Matrix Interpretation Processor: dim=3 interpretation: [1 1 1] [1 1 0] [1] [f](x0, x1) = [0 0 0]x0 + [0 0 0]x1 + [0] [0 0 0] [0 0 0] [0], [1 1 1] [1] [s](x0) = [1 1 1]x0 + [0] [1 1 1] [0] orientation: [3 3 3] [1 1 0] [2] [3 3 3] [2] f(s(x),y) = [0 0 0]x + [0 0 0]y + [0] >= [0 0 0]x + [0] = f(x,s(x)) [0 0 0] [0 0 0] [0] [0 0 0] [0] [1 1 1] [2 2 2] [2] [1 1 0] [1 1 1] [1] f(x,s(y)) = [0 0 0]x + [0 0 0]y + [0] >= [0 0 0]x + [0 0 0]y + [0] = f(y,x) [0 0 0] [0 0 0] [0] [0 0 0] [0 0 0] [0] problem: f(s(x),y) -> f(x,s(x)) Matrix Interpretation Processor: dim=3 interpretation: [1 0 1] [1 0 0] [f](x0, x1) = [0 0 0]x0 + [0 0 0]x1 [0 0 0] [0 0 0] , [1 0 0] [0] [s](x0) = [0 0 0]x0 + [0] [1 0 1] [1] orientation: [2 0 1] [1 0 0] [1] [2 0 1] f(s(x),y) = [0 0 0]x + [0 0 0]y + [0] >= [0 0 0]x = f(x,s(x)) [0 0 0] [0 0 0] [0] [0 0 0] problem: Qed