NO

Initial ITS

Start location: [1]
Program variables: a b olda
   0: [1] -> [2] : a'=nondet, T, cost: 1
   1: [2] -> [3] : b'=nondet1, T, cost: 1
   2: [3] -> [4] : -7+a >= 0, cost: 1
   7: [3] -> [8] : -7+a < 0, cost: 1
   3: [4] -> [5] : olda'=a, T, cost: 1
   4: [5] -> [6] : a'=b, T, cost: 1
   5: [6] -> [7] : b'=1+olda, T, cost: 1
   6: [7] -> [3] : T, cost: 1

Chained Linear Paths

Start location: [1]
Program variables: a b olda
   8: [1] -> [3] : a'=nondet, b'=nondet1, T, cost: 1
   7: [3] -> [8] : -7+a < 0, cost: 1
  12: [3] -> [3] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1

	Eliminating location [2] by chaining:

	Applied chaining

	First rule:
	[1] -> [2] : a'=nondet, T, cost: 1
	Second rule:
	[2] -> [3] : b'=nondet1, T, cost: 1
	New rule:
	[1] -> [3] : a'=nondet, b'=nondet1, T, cost: 1
	
	Applied deletion

	Removed the following rules: 0 1
	
	Eliminating location [4] by chaining:

	Applied chaining

	First rule:
	[3] -> [4] : -7+a >= 0, cost: 1
	Second rule:
	[4] -> [5] : olda'=a, T, cost: 1
	New rule:
	[3] -> [5] : olda'=a, -7+a >= 0, cost: 1
	
	Applied deletion

	Removed the following rules: 2 3
	
	Eliminating location [5] by chaining:

	Applied chaining

	First rule:
	[3] -> [5] : olda'=a, -7+a >= 0, cost: 1
	Second rule:
	[5] -> [6] : a'=b, T, cost: 1
	New rule:
	[3] -> [6] : a'=b, olda'=a, -7+a >= 0, cost: 1
	
	Applied deletion

	Removed the following rules: 4 9
	
	Eliminating location [6] by chaining:

	Applied chaining

	First rule:
	[3] -> [6] : a'=b, olda'=a, -7+a >= 0, cost: 1
	Second rule:
	[6] -> [7] : b'=1+olda, T, cost: 1
	New rule:
	[3] -> [7] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1
	
	Applied deletion

	Removed the following rules: 5 10
	
	Eliminating location [7] by chaining:

	Applied chaining

	First rule:
	[3] -> [7] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1
	Second rule:
	[7] -> [3] : T, cost: 1
	New rule:
	[3] -> [3] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1
	
	Applied deletion

	Removed the following rules: 6 11

Unrolled Loops

Start location: [1]
Program variables: a b olda
   8: [1] -> [3] : a'=nondet, b'=nondet1, T, cost: 1
   7: [3] -> [8] : -7+a < 0, cost: 1
  12: [3] -> [3] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1
  13: [3] -> [3] : a'=1+a, b'=1+b, olda'=b, (-7+b >= 0 /\ -7+a >= 0), cost: 1

	Unrolling

	Original rule:
	[3] -> [3] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1
	New rule:
	[3] -> [3] : a'=1+a, b'=1+b, olda'=b, (-7+b >= 0 /\ -7+a >= 0), cost: 1

Step with 8

	Trace

	8[T]
	
	Blocked

	[{}, {}]

Step with 7

	Trace

	8[T], 7[(-7+a < 0)]
	
	Blocked

	[{}, {}, {}]

Backtrack

	Trace

	8[T]
	
	Blocked

	[{}, {7[T]}]

Step with 12

	Trace

	8[T], 12[(-7+a >= 0)]
	
	Blocked

	[{}, {7[T]}, {}]

Nonterm

Start location: [1]
Program variables: a b olda
   8: [1] -> [3] : a'=nondet, b'=nondet1, T, cost: 1
   7: [3] -> [8] : -7+a < 0, cost: 1
  12: [3] -> [3] : a'=b, b'=1+a, olda'=a, -7+a >= 0, cost: 1
  13: [3] -> [3] : a'=1+a, b'=1+b, olda'=b, (-7+b >= 0 /\ -7+a >= 0), cost: 1
  14: [3] -> LoAT_sink : (-7+b >= 0 /\ -7+a >= 0 /\ -1+n >= 0), cost: NONTERM
  15: [3] -> [3] : a'=n+a, b'=b+n, olda'=-1+b+n, (-7+b >= 0 /\ -7+a >= 0 /\ -1+n >= 0), cost: 1

	unrolling

	Original rule:
	[3] -> [3] : a'=b, b'=1+a, olda'=a, (-7+a >= 0), cost: 1
	New rule:
	[3] -> [3] : a'=1+a, b'=1+b, olda'=b, (-7+b >= 0 /\ -7+a >= 0), cost: 1
	
	Certificate of Non-Termination

	Original rule:
	[3] -> [3] : a'=1+a, b'=1+b, olda'=b, (-7+b >= 0 /\ -7+a >= 0), cost: 1
	New rule:
	[3] -> LoAT_sink : (-7+b >= 0 /\ -7+a >= 0 /\ -1+n >= 0), cost: NONTERM

		-7+b >= 0 [0]: monotonic increase yields -7+b >= 0
		
		-7+a >= 0 [0]: monotonic increase yields -7+a >= 0
		
		Replacement map: {-7+b >= 0 -> -7+b >= 0, -7+a >= 0 -> -7+a >= 0}

	Loop Acceleration

	Original rule:
	[3] -> [3] : a'=1+a, b'=1+b, olda'=b, (-7+b >= 0 /\ -7+a >= 0), cost: 1
	New rule:
	[3] -> [3] : a'=n+a, b'=b+n, olda'=-1+b+n, (-7+b >= 0 /\ -7+a >= 0 /\ -1+n >= 0), cost: 1

		-7+b >= 0 [0]: monotonic increase yields -7+b >= 0
		
		-7+a >= 0 [0]: monotonic increase yields -7+a >= 0
		
		Replacement map: {-7+b >= 0 -> -7+b >= 0, -7+a >= 0 -> -7+a >= 0}

Step with 14

	Trace

	8[T], 14[(-7+b >= 0 /\ -7+a >= 0 /\ -1+n >= 0)]
	
	Blocked

	[{}, {7[T]}, {14[T]}]

Refute

	Counterexample

	[ a=7 b=7 olda=0 ] 8 [ a=a b=b olda=0 ] 14
	
NO

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