LTS Termination Proof

by T2Cert

Input

Integer Transition System

Initial Location: 3

Transitions: (pre-variables and post-variables)

0	0	1:	0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ x_0 ≤ 0 ∧ − x_0 + x_1 ≤ 0 ∧ x_0 − x_1 ≤ 0 ∧ − x_1 + x_2 ≤ 0 ∧ x_1 − x_2 ≤ 0 ∧ − x_2 + x_3 ≤ 0 ∧ x_2 − x_3 ≤ 0 ∧ − x_3 + x_post ≤ 0 ∧ x_3 − x_post ≤ 0 ∧ x_0 − x_post ≤ 0 ∧ − x_0 + x_post ≤ 0
0	1	2:	0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 0 ≤ 0 ∧ 1 − x_0 ≤ 0 ∧ − x_0 + x_1 ≤ 0 ∧ x_0 − x_1 ≤ 0 ∧ 1 − x_1 + x_post ≤ 0 ∧ −1 + x_1 − x_post ≤ 0 ∧ x_0 − x_post ≤ 0 ∧ − x_0 + x_post ≤ 0 ∧ − x_3 + x_3 ≤ 0 ∧ x_3 − x_3 ≤ 0 ∧ − x_2 + x_2 ≤ 0 ∧ x_2 − x_2 ≤ 0
2	2	0:	0 ≤ 0 ∧ 0 ≤ 0 ∧ − x_0 + x_post ≤ 0 ∧ x_0 − x_post ≤ 0 ∧ x_0 − x_post ≤ 0 ∧ − x_0 + x_post ≤ 0 ∧ − x_3 + x_3 ≤ 0 ∧ x_3 − x_3 ≤ 0 ∧ − x_2 + x_2 ≤ 0 ∧ x_2 − x_2 ≤ 0 ∧ − x_1 + x_1 ≤ 0 ∧ x_1 − x_1 ≤ 0
3	3	2:	0 ≤ 0 ∧ 0 ≤ 0 ∧ − x_post + x_post ≤ 0 ∧ x_post − x_post ≤ 0 ∧ − x_3 + x_3 ≤ 0 ∧ x_3 − x_3 ≤ 0 ∧ − x_2 + x_2 ≤ 0 ∧ x_2 − x_2 ≤ 0 ∧ − x_1 + x_1 ≤ 0 ∧ x_1 − x_1 ≤ 0 ∧ − x_0 + x_0 ≤ 0 ∧ x_0 − x_0 ≤ 0

Proof

1 Invariant Updates

The following invariants are asserted.

0:	TRUE
1:	x_0 ≤ 0 ∧ x_post ≤ 0 ∧ x_1 ≤ 0 ∧ x_2 ≤ 0 ∧ x_3 ≤ 0
2:	TRUE
3:	TRUE

The invariants are proved as follows.

IMPACT Invariant Proof

nodes (location) invariant:

0	(0)	TRUE
1	(1)	x_0 ≤ 0 ∧ x_post ≤ 0 ∧ x_1 ≤ 0 ∧ x_2 ≤ 0 ∧ x_3 ≤ 0
2	(2)	TRUE
3	(3)	TRUE

initial node: 3
cover edges:
transition edges:

0 0 1

0 1 2

2 2 0

3 3 2

2 Switch to Cooperation Termination Proof

We consider the following cutpoint-transitions:

− x_post + x_post ≤ 0 ∧ x_post − x_post ≤ 0 ∧ − x_3 + x_3 ≤ 0 ∧ x_3 − x_3 ≤ 0 ∧ − x_2 + x_2 ≤ 0 ∧ x_2 − x_2 ≤ 0 ∧ − x_1 + x_1 ≤ 0 ∧ x_1 − x_1 ≤ 0 ∧ − x_0 + x_0 ≤ 0 ∧ x_0 − x_0 ≤ 0

and for every transition t, a duplicate t is considered.

3 Transition Removal

We remove transitions 0, 3 using the following ranking functions, which are bounded by −11.

3:	0
0:	0
2:	0
1:	0
3:	−4
0:	−5
2:	−5
2_var_snapshot:	−5
2*:	−5
1:	−6

4 Location Addition

The following skip-transition is inserted and corresponding redirections w.r.t. the old location are performed.

2* 7 2: − x_post + x_post ≤ 0 ∧ x_post − x_post ≤ 0 ∧ − x_3 + x_3 ≤ 0 ∧ x_3 − x_3 ≤ 0 ∧ − x_2 + x_2 ≤ 0 ∧ x_2 − x_2 ≤ 0 ∧ − x_1 + x_1 ≤ 0 ∧ x_1 − x_1 ≤ 0 ∧ − x_0 + x_0 ≤ 0 ∧ x_0 − x_0 ≤ 0

5 Location Addition

The following skip-transition is inserted and corresponding redirections w.r.t. the old location are performed.

2 5 2_var_snapshot: − x_post + x_post ≤ 0 ∧ x_post − x_post ≤ 0 ∧ − x_3 + x_3 ≤ 0 ∧ x_3 − x_3 ≤ 0 ∧ − x_2 + x_2 ≤ 0 ∧ x_2 − x_2 ≤ 0 ∧ − x_1 + x_1 ≤ 0 ∧ x_1 − x_1 ≤ 0 ∧ − x_0 + x_0 ≤ 0 ∧ x_0 − x_0 ≤ 0

6 SCC Decomposition

We consider subproblems for each of the 1 SCC(s) of the program graph.

6.1 SCC Subproblem 1/1

Here we consider the SCC { 0, 2, 2_var_snapshot, 2* }.

6.1.1 Transition Removal

We remove transition 1 using the following ranking functions, which are bounded by 2.

0:	−1 + 4⋅x_0
2:	1 + 4⋅x_0
2_var_snapshot:	4⋅x_0
2*:	2 + 4⋅x_0

6.1.2 Transition Removal

We remove transitions 5, 7, 2 using the following ranking functions, which are bounded by −1.

0:	−1
2:	1
2_var_snapshot:	0
2*:	2

6.1.3 Splitting Cut-Point Transitions

We consider 1 subproblems corresponding to sets of cut-point transitions as follows.

6.1.3.1 Cut-Point Subproblem 1/1

Here we consider cut-point transition 4.

6.1.3.1.1 Splitting Cut-Point Transitions

There remain no cut-point transition to consider. Hence the cooperation termination is trivial.

Tool configuration

T2Cert

version: 1.0