YES(?,O(n^2)) Problem: f(f(X)) -> f(g(f(g(f(X))))) f(g(f(X))) -> f(g(X)) Proof: RT Transformation Processor: strict: f(f(X)) -> f(g(f(g(f(X))))) f(g(f(X))) -> f(g(X)) weak: Matrix Interpretation Processor: dimension: 1 interpretation: [g](x0) = x0 + 1, [f](x0) = x0 + 1 orientation: f(f(X)) = X + 2 >= X + 5 = f(g(f(g(f(X))))) f(g(f(X))) = X + 3 >= X + 2 = f(g(X)) problem: strict: f(f(X)) -> f(g(f(g(f(X))))) weak: f(g(f(X))) -> f(g(X)) Matrix Interpretation Processor: dimension: 2 interpretation: [1 1] [1] [g](x0) = [0 0]x0 + [0], [1 4] [1] [f](x0) = [0 0]x0 + [4] orientation: [1 4] [18] [1 4] [13] f(f(X)) = [0 0]X + [4 ] >= [0 0]X + [4 ] = f(g(f(g(f(X))))) [1 4] [7] [1 1] [2] f(g(f(X))) = [0 0]X + [4] >= [0 0]X + [4] = f(g(X)) problem: strict: weak: f(f(X)) -> f(g(f(g(f(X))))) f(g(f(X))) -> f(g(X)) Qed