YES Problem: strict: f(g(f(x))) -> f(g(g(g(f(x))))) weak: g(x) -> g(g(x)) g(x) -> g(g(f(g(g(x))))) f(x) -> g(g(f(g(g(x))))) Proof: Matrix Interpretation Processor: dim=3 interpretation: [1 0 0] [g](x0) = [0 0 1]x0 [0 0 0] , [1 2 0] [0] [f](x0) = [2 2 2]x0 + [0] [0 0 0] [1] orientation: [1 2 0] [2] [1 2 0] [0] f(g(f(x))) = [2 4 0]x + [2] >= [2 4 0]x + [0] = f(g(g(g(f(x))))) [0 0 0] [1] [0 0 0] [1] [1 0 0] [1 0 0] g(x) = [0 0 1]x >= [0 0 0]x = g(g(x)) [0 0 0] [0 0 0] [1 0 0] [1 0 0] g(x) = [0 0 1]x >= [0 0 0]x = g(g(f(g(g(x))))) [0 0 0] [0 0 0] [1 2 0] [0] [1 0 0] f(x) = [2 2 2]x + [0] >= [0 0 0]x = g(g(f(g(g(x))))) [0 0 0] [1] [0 0 0] problem: strict: weak: g(x) -> g(g(x)) g(x) -> g(g(f(g(g(x))))) f(x) -> g(g(f(g(g(x))))) Qed