NO Initial ITS Start location: [1] Program variables: x y 0: [1] -> [2] : x'=1, T, cost: 1 1: [2] -> [3] : y'=1, T, cost: 1 2: [3] -> [4] : x >= 0, cost: 1 6: [3] -> [7] : x < 0, cost: 1 3: [4] -> [5] : x'=2*x, T, cost: 1 4: [5] -> [6] : y'=3*y, T, cost: 1 5: [6] -> [3] : T, cost: 1 Chained Linear Paths Start location: [1] Program variables: x y 7: [1] -> [3] : x'=1, y'=1, T, cost: 1 6: [3] -> [7] : x < 0, cost: 1 10: [3] -> [3] : x'=2*x, y'=3*y, x >= 0, cost: 1 Eliminating location [2] by chaining: Applied chaining First rule: [1] -> [2] : x'=1, T, cost: 1 Second rule: [2] -> [3] : y'=1, T, cost: 1 New rule: [1] -> [3] : x'=1, y'=1, T, cost: 1 Applied deletion Removed the following rules: 0 1 Eliminating location [4] by chaining: Applied chaining First rule: [3] -> [4] : x >= 0, cost: 1 Second rule: [4] -> [5] : x'=2*x, T, cost: 1 New rule: [3] -> [5] : x'=2*x, x >= 0, cost: 1 Applied deletion Removed the following rules: 2 3 Eliminating location [5] by chaining: Applied chaining First rule: [3] -> [5] : x'=2*x, x >= 0, cost: 1 Second rule: [5] -> [6] : y'=3*y, T, cost: 1 New rule: [3] -> [6] : x'=2*x, y'=3*y, x >= 0, cost: 1 Applied deletion Removed the following rules: 4 8 Eliminating location [6] by chaining: Applied chaining First rule: [3] -> [6] : x'=2*x, y'=3*y, x >= 0, cost: 1 Second rule: [6] -> [3] : T, cost: 1 New rule: [3] -> [3] : x'=2*x, y'=3*y, x >= 0, cost: 1 Applied deletion Removed the following rules: 5 9 Step with 7 Trace 7[T] Blocked [{}, {}] Step with 10 Trace 7[T], 10[(x >= 0)] Blocked [{}, {6[T]}, {}] Nonterm Start location: [1] Program variables: x y 7: [1] -> [3] : x'=1, y'=1, T, cost: 1 6: [3] -> [7] : x < 0, cost: 1 10: [3] -> [3] : x'=2*x, y'=3*y, x >= 0, cost: 1 11: [3] -> LoAT_sink : (x >= 0 /\ -1+n >= 0), cost: NONTERM 12: [3] -> [3] : x'=2^n*x, y'=y*3^n, (x >= 0 /\ -1+n >= 0), cost: 1 Certificate of Non-Termination Original rule: [3] -> [3] : x'=2*x, y'=3*y, (x >= 0), cost: 1 New rule: [3] -> LoAT_sink : (x >= 0 /\ -1+n >= 0), cost: NONTERM x >= 0 [0]: monotonic increase yields x >= 0 Replacement map: {x >= 0 -> x >= 0} Loop Acceleration Original rule: [3] -> [3] : x'=2*x, y'=3*y, (x >= 0), cost: 1 New rule: [3] -> [3] : x'=2^n*x, y'=y*3^n, (x >= 0 /\ -1+n >= 0), cost: 1 x >= 0 [0]: monotonic increase yields x >= 0 Replacement map: {x >= 0 -> x >= 0} Step with 11 Trace 7[T], 11[(x >= 0 /\ -1+n >= 0)] Blocked [{}, {6[T]}, {11[T]}] Refute Counterexample [ x=1 y=1 ] 7 [ x=x y=y ] 11 NO Build SHA: a05f16bf13df659c382799650051f91bf6828c7b