NO Initial ITS Start location: [1] Program variables: i j 0: [1] -> [2] : i'=0, T, cost: 1 1: [2] -> [3] : -100+i < 0, cost: 1 9: [2] -> [9] : -100+i >= 0, cost: 1 2: [3] -> [4] : j'=0, T, cost: 1 3: [4] -> [5] : -1+j < 0, cost: 1 6: [4] -> [7] : -1+j >= 0, cost: 1 4: [5] -> [6] : j'=1+j, T, cost: 1 5: [6] -> [4] : T, cost: 1 7: [7] -> [8] : i'=i, T, cost: 1 8: [8] -> [2] : T, cost: 1 Chained Linear Paths Start location: [1] Program variables: i j 0: [1] -> [2] : i'=0, T, cost: 1 9: [2] -> [9] : -100+i >= 0, cost: 1 10: [2] -> [4] : j'=0, -100+i < 0, cost: 1 13: [4] -> [4] : j'=1+j, -1+j < 0, cost: 1 14: [4] -> [2] : i'=i, -1+j >= 0, cost: 1 Eliminating location [3] by chaining: Applied chaining First rule: [2] -> [3] : -100+i < 0, cost: 1 Second rule: [3] -> [4] : j'=0, T, cost: 1 New rule: [2] -> [4] : j'=0, -100+i < 0, cost: 1 Applied deletion Removed the following rules: 1 2 Eliminating location [5] by chaining: Applied chaining First rule: [4] -> [5] : -1+j < 0, cost: 1 Second rule: [5] -> [6] : j'=1+j, T, cost: 1 New rule: [4] -> [6] : j'=1+j, -1+j < 0, cost: 1 Applied deletion Removed the following rules: 3 4 Eliminating location [7] by chaining: Applied chaining First rule: [4] -> [7] : -1+j >= 0, cost: 1 Second rule: [7] -> [8] : i'=i, T, cost: 1 New rule: [4] -> [8] : i'=i, -1+j >= 0, cost: 1 Applied deletion Removed the following rules: 6 7 Eliminating location [6] by chaining: Applied chaining First rule: [4] -> [6] : j'=1+j, -1+j < 0, cost: 1 Second rule: [6] -> [4] : T, cost: 1 New rule: [4] -> [4] : j'=1+j, -1+j < 0, cost: 1 Applied deletion Removed the following rules: 5 11 Eliminating location [8] by chaining: Applied chaining First rule: [4] -> [8] : i'=i, -1+j >= 0, cost: 1 Second rule: [8] -> [2] : T, cost: 1 New rule: [4] -> [2] : i'=i, -1+j >= 0, cost: 1 Applied deletion Removed the following rules: 8 12 Simplified Transitions Start location: [1] Program variables: i j 0: [1] -> [2] : i'=0, T, cost: 1 9: [2] -> [9] : -100+i >= 0, cost: 1 10: [2] -> [4] : j'=0, -100+i < 0, cost: 1 13: [4] -> [4] : j'=1+j, -1+j < 0, cost: 1 15: [4] -> [2] : -1+j >= 0, cost: 1 Removed Trivial Updates Original rule: [4] -> [2] : i'=i, -1+j >= 0, cost: 1 New rule: [4] -> [2] : -1+j >= 0, cost: 1 Step with 0 Trace 0[T] Blocked [{}, {}] Step with 10 Trace 0[T], 10[(-100+i < 0)] Blocked [{}, {9[T]}, {}] Step with 13 Trace 0[T], 10[(-100+i < 0)], 13[(-1+j < 0)] Blocked [{}, {9[T]}, {}, {}] Accelerate Start location: [1] Program variables: i j 0: [1] -> [2] : i'=0, T, cost: 1 9: [2] -> [9] : -100+i >= 0, cost: 1 10: [2] -> [4] : j'=0, -100+i < 0, cost: 1 13: [4] -> [4] : j'=1+j, -1+j < 0, cost: 1 15: [4] -> [2] : -1+j >= 0, cost: 1 16: [4] -> [4] : j'=n+j, (-1+n >= 0 /\ 2-n-j > 0), cost: 1 Loop Acceleration Original rule: [4] -> [4] : j'=1+j, (-1+j < 0), cost: 1 New rule: [4] -> [4] : j'=n+j, (-1+n >= 0 /\ 2-n-j > 0), cost: 1 1-j > 0 [0]: montonic decrease yields 2-n-j > 0 1-j > 0 [1]: eventual increase yields (1 <= 0 /\ 1-j > 0) Replacement map: {1-j > 0 -> 2-n-j > 0} Trace 0[T], 10[(-100+i < 0)], 16[(-1+n >= 0 /\ 2-n-j > 0)] Blocked [{}, {9[T]}, {}, {13[T], 16[T]}] Step with 15 Trace 0[T], 10[(-100+i < 0)], 16[(-1+n >= 0 /\ 2-n-j > 0)], 15[(-1+j >= 0)] Blocked [{}, {9[T]}, {}, {13[T], 16[T]}, {}] Nonterm Start location: [1] Program variables: i j 0: [1] -> [2] : i'=0, T, cost: 1 9: [2] -> [9] : -100+i >= 0, cost: 1 10: [2] -> [4] : j'=0, -100+i < 0, cost: 1 17: [2] -> LoAT_sink : (100-i > 0 /\ -1+n2 >= 0), cost: NONTERM 13: [4] -> [4] : j'=1+j, -1+j < 0, cost: 1 15: [4] -> [2] : -1+j >= 0, cost: 1 16: [4] -> [4] : j'=n+j, (-1+n >= 0 /\ 2-n-j > 0), cost: 1 Certificate of Non-Termination Original rule: [2] -> [2] : j'=1, -100+i < 0, cost: 1 New rule: [2] -> LoAT_sink : (100-i > 0 /\ -1+n2 >= 0), cost: NONTERM 100-i > 0 [0]: monotonic increase yields 100-i > 0 Replacement map: {100-i > 0 -> 100-i > 0} Step with 17 Trace 0[T], 17[(100-i > 0 /\ -1+n2 >= 0)] Blocked [{}, {9[T]}, {17[T]}] Refute Counterexample [ i=0 j=0 ] 0 [ i=i j=0 ] 17 NO Build SHA: a05f16bf13df659c382799650051f91bf6828c7b