NO Initial ITS Start location: l4 Program variables: x_5^0 0: l0 -> l1 : x_5^0'=x_5^post1, -x_5^post1+x_5^0 == 0, cost: 1 1: l1 -> l2 : x_5^0'=x_5^post2, (1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 3: l1 -> l3 : x_5^0'=x_5^post4, (1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0), cost: 1 2: l2 -> l1 : x_5^0'=x_5^post3, -x_5^post3+x_5^0 == 0, cost: 1 4: l3 -> l1 : x_5^0'=x_5^post5, x_5^0-x_5^post5 == 0, cost: 1 5: l4 -> l0 : x_5^0'=x_5^post6, -x_5^post6+x_5^0 == 0, cost: 1 Chained Linear Paths Start location: l4 Program variables: x_5^0 7: l1 -> l1 : x_5^0'=x_5^post3, (-x_5^post3+x_5^post2 == 0 /\ 1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 8: l1 -> l1 : x_5^0'=x_5^post5, (1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0 /\ x_5^post4-x_5^post5 == 0), cost: 1 6: l4 -> l1 : x_5^0'=x_5^post1, (x_5^post6-x_5^post1 == 0 /\ -x_5^post6+x_5^0 == 0), cost: 1 Eliminating location l0 by chaining: Applied chaining First rule: l4 -> l0 : x_5^0'=x_5^post6, -x_5^post6+x_5^0 == 0, cost: 1 Second rule: l0 -> l1 : x_5^0'=x_5^post1, -x_5^post1+x_5^0 == 0, cost: 1 New rule: l4 -> l1 : x_5^0'=x_5^post1, (x_5^post6-x_5^post1 == 0 /\ -x_5^post6+x_5^0 == 0), cost: 1 Applied deletion Removed the following rules: 0 5 Eliminating location l2 by chaining: Applied chaining First rule: l1 -> l2 : x_5^0'=x_5^post2, (1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 Second rule: l2 -> l1 : x_5^0'=x_5^post3, -x_5^post3+x_5^0 == 0, cost: 1 New rule: l1 -> l1 : x_5^0'=x_5^post3, (-x_5^post3+x_5^post2 == 0 /\ 1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 Applied deletion Removed the following rules: 1 2 Eliminating location l3 by chaining: Applied chaining First rule: l1 -> l3 : x_5^0'=x_5^post4, (1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0), cost: 1 Second rule: l3 -> l1 : x_5^0'=x_5^post5, x_5^0-x_5^post5 == 0, cost: 1 New rule: l1 -> l1 : x_5^0'=x_5^post5, (1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0 /\ x_5^post4-x_5^post5 == 0), cost: 1 Applied deletion Removed the following rules: 3 4 Simplified Transitions Start location: l4 Program variables: x_5^0 10: l1 -> l1 : x_5^0'=-1+x_5^0, -1+x_5^0 <= 0, cost: 1 11: l1 -> l1 : x_5^0'=-1+x_5^0, 2-x_5^0 <= 0, cost: 1 9: l4 -> l1 : T, cost: 1 Propagated Equalities Original rule: l4 -> l1 : x_5^0'=x_5^post1, (x_5^post6-x_5^post1 == 0 /\ -x_5^post6+x_5^0 == 0), cost: 1 New rule: l4 -> l1 : x_5^0'=x_5^post6, (0 == 0 /\ -x_5^post6+x_5^0 == 0), cost: 1 propagated equality x_5^post1 = x_5^post6 Propagated Equalities Original rule: l4 -> l1 : x_5^0'=x_5^post6, (0 == 0 /\ -x_5^post6+x_5^0 == 0), cost: 1 New rule: l4 -> l1 : x_5^0'=x_5^0, 0 == 0, cost: 1 propagated equality x_5^post6 = x_5^0 Simplified Guard Original rule: l4 -> l1 : x_5^0'=x_5^0, 0 == 0, cost: 1 New rule: l4 -> l1 : x_5^0'=x_5^0, T, cost: 1 Removed Trivial Updates Original rule: l4 -> l1 : x_5^0'=x_5^0, T, cost: 1 New rule: l4 -> l1 : T, cost: 1 Propagated Equalities Original rule: l1 -> l1 : x_5^0'=x_5^post3, (-x_5^post3+x_5^post2 == 0 /\ 1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 New rule: l1 -> l1 : x_5^0'=x_5^post2, (0 == 0 /\ 1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 propagated equality x_5^post3 = x_5^post2 Propagated Equalities Original rule: l1 -> l1 : x_5^0'=x_5^post2, (0 == 0 /\ 1-x_5^0+x_5^post2 == 0 /\ x_5^post2 <= 0), cost: 1 New rule: l1 -> l1 : x_5^0'=-1+x_5^0, (0 == 0 /\ -1+x_5^0 <= 0), cost: 1 propagated equality x_5^post2 = -1+x_5^0 Simplified Guard Original rule: l1 -> l1 : x_5^0'=-1+x_5^0, (0 == 0 /\ -1+x_5^0 <= 0), cost: 1 New rule: l1 -> l1 : x_5^0'=-1+x_5^0, -1+x_5^0 <= 0, cost: 1 Propagated Equalities Original rule: l1 -> l1 : x_5^0'=x_5^post5, (1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0 /\ x_5^post4-x_5^post5 == 0), cost: 1 New rule: l1 -> l1 : x_5^0'=x_5^post4, (0 == 0 /\ 1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0), cost: 1 propagated equality x_5^post5 = x_5^post4 Propagated Equalities Original rule: l1 -> l1 : x_5^0'=x_5^post4, (0 == 0 /\ 1-x_5^post4 <= 0 /\ 1+x_5^post4-x_5^0 == 0), cost: 1 New rule: l1 -> l1 : x_5^0'=-1+x_5^0, (0 == 0 /\ 2-x_5^0 <= 0), cost: 1 propagated equality x_5^post4 = -1+x_5^0 Simplified Guard Original rule: l1 -> l1 : x_5^0'=-1+x_5^0, (0 == 0 /\ 2-x_5^0 <= 0), cost: 1 New rule: l1 -> l1 : x_5^0'=-1+x_5^0, 2-x_5^0 <= 0, cost: 1 Step with 9 Trace 9[T] Blocked [{}, {}] Step with 10 Trace 9[T], 10[(-1+x_5^0 <= 0)] Blocked [{}, {}, {}] Nonterm Start location: l4 Program variables: x_5^0 10: l1 -> l1 : x_5^0'=-1+x_5^0, -1+x_5^0 <= 0, cost: 1 11: l1 -> l1 : x_5^0'=-1+x_5^0, 2-x_5^0 <= 0, cost: 1 12: l1 -> LoAT_sink : (1-x_5^0 >= 0 /\ -1+n >= 0), cost: NONTERM 13: l1 -> l1 : x_5^0'=-n+x_5^0, (1-x_5^0 >= 0 /\ -1+n >= 0), cost: 1 9: l4 -> l1 : T, cost: 1 Certificate of Non-Termination Original rule: l1 -> l1 : x_5^0'=-1+x_5^0, (-1+x_5^0 <= 0), cost: 1 New rule: l1 -> LoAT_sink : (1-x_5^0 >= 0 /\ -1+n >= 0), cost: NONTERM 1-x_5^0 >= 0 [0]: monotonic increase yields 1-x_5^0 >= 0 Replacement map: {1-x_5^0 >= 0 -> 1-x_5^0 >= 0} Loop Acceleration Original rule: l1 -> l1 : x_5^0'=-1+x_5^0, (-1+x_5^0 <= 0), cost: 1 New rule: l1 -> l1 : x_5^0'=-n+x_5^0, (1-x_5^0 >= 0 /\ -1+n >= 0), cost: 1 1-x_5^0 >= 0 [0]: monotonic increase yields 1-x_5^0 >= 0 Replacement map: {1-x_5^0 >= 0 -> 1-x_5^0 >= 0} Step with 12 Trace 9[T], 12[(1-x_5^0 >= 0 /\ -1+n >= 0)] Blocked [{}, {}, {12[T]}] Refute Counterexample [ x_5^0=0 ] 9 [ x_5^0=0 ] 12 NO Build SHA: a05f16bf13df659c382799650051f91bf6828c7b