NO Initial ITS Start location: [1] Program variables: x 0: [1] -> [2] : x'=nondet, T, cost: 1 1: [2] -> [3] : x >= 0, cost: 1 4: [2] -> [5] : x < 0, cost: 1 2: [3] -> [4] : x'=nondet1+x, T, cost: 1 3: [4] -> [2] : T, cost: 1 Chained Linear Paths Start location: [1] Program variables: x 0: [1] -> [2] : x'=nondet, T, cost: 1 4: [2] -> [5] : x < 0, cost: 1 6: [2] -> [2] : x'=nondet1+x, x >= 0, cost: 1 Eliminating location [3] by chaining: Applied chaining First rule: [2] -> [3] : x >= 0, cost: 1 Second rule: [3] -> [4] : x'=nondet1+x, T, cost: 1 New rule: [2] -> [4] : x'=nondet1+x, x >= 0, cost: 1 Applied deletion Removed the following rules: 1 2 Eliminating location [4] by chaining: Applied chaining First rule: [2] -> [4] : x'=nondet1+x, x >= 0, cost: 1 Second rule: [4] -> [2] : T, cost: 1 New rule: [2] -> [2] : x'=nondet1+x, x >= 0, cost: 1 Applied deletion Removed the following rules: 3 5 Step with 0 Trace 0[T] Blocked [{}, {}] Step with 4 Trace 0[T], 4[(x < 0)] Blocked [{}, {}, {}] Backtrack Trace 0[T] Blocked [{}, {4[T]}] Step with 6 Trace 0[T], 6[(x >= 0)] Blocked [{}, {4[T]}, {}] Nonterm Start location: [1] Program variables: x 0: [1] -> [2] : x'=nondet, T, cost: 1 4: [2] -> [5] : x < 0, cost: 1 6: [2] -> [2] : x'=nondet1+x, x >= 0, cost: 1 7: [2] -> LoAT_sink : (-nondet1 <= 0 /\ x >= 0), cost: NONTERM 8: [2] -> [2] : x'=nondet1*n+x, (-1+n >= 0 /\ (-1+n)*nondet1+x >= 0 /\ x >= 0), cost: 1 Certificate of Non-Termination Original rule: [2] -> [2] : x'=nondet1+x, (x >= 0), cost: 1 New rule: [2] -> LoAT_sink : (-nondet1 <= 0 /\ x >= 0), cost: NONTERM x >= 0 [0]: eventual decrease yields ((-1+n)*nondet1+x >= 0 /\ x >= 0) x >= 0 [1]: eventual increase yields (-nondet1 <= 0 /\ x >= 0) Replacement map: {x >= 0 -> (-nondet1 <= 0 /\ x >= 0)} Loop Acceleration Original rule: [2] -> [2] : x'=nondet1+x, (x >= 0), cost: 1 New rule: [2] -> [2] : x'=nondet1*n+x, (-1+n >= 0 /\ (-1+n)*nondet1+x >= 0 /\ x >= 0), cost: 1 x >= 0 [0]: eventual decrease yields ((-1+n)*nondet1+x >= 0 /\ x >= 0) x >= 0 [1]: eventual increase yields (-nondet1 <= 0 /\ x >= 0) Replacement map: {x >= 0 -> ((-1+n)*nondet1+x >= 0 /\ x >= 0)} Step with 7 Trace 0[T], 7[(-nondet1 <= 0 /\ x >= 0)] Blocked [{}, {4[T]}, {7[T]}] Refute Counterexample [ x=0 ] 0 [ x=x ] 7 NO Build SHA: a05f16bf13df659c382799650051f91bf6828c7b