MAYBE Initial complexity problem: 1: T: (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ Ar_0 >= 2 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ 1 >= Ar_0 ] (Comp: ?, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 - 1, Ar_1, Ar_2, Fresh_1, Ar_4)) [ 0 >= Fresh_1 /\ Fresh_1 >= 1 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ Fresh_0 >= 1 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ 0 >= Ar_1 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Testing for reachability in the complexity graph removes the following transition from problem 1: f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 - 1, Ar_1, Ar_2, Fresh_1, Ar_4)) [ 0 >= Fresh_1 /\ Fresh_1 >= 1 ] We thus obtain the following problem: 2: T: (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ 0 >= Ar_1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ 1 >= Ar_0 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ Fresh_0 >= 1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ Ar_0 >= 2 ] (Comp: ?, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Repeatedly propagating knowledge in problem 2 produces the following problem: 3: T: (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ 0 >= Ar_1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ 1 >= Ar_0 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ Fresh_0 >= 1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ Ar_0 >= 2 ] (Comp: 1, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f5) = 1 Pol(f3) = 0 Pol(f4) = 1 Pol(f30) = 1 Pol(koat_start) = 1 orients all transitions weakly and the transition f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ 0 >= Ar_1 ] strictly and produces the following problem: 4: T: (Comp: 1, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ 0 >= Ar_1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ 1 >= Ar_0 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ Fresh_0 >= 1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ Ar_0 >= 2 ] (Comp: 1, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f5) = -3*V_1 + 2 Pol(f3) = -3*V_1 + 2 Pol(f4) = -3*V_1 + 4 Pol(f30) = 0 Pol(koat_start) = 0 orients all transitions weakly and the transition f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ 1 >= Ar_0 ] strictly and produces the following problem: 5: T: (Comp: 1, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ 0 >= Ar_1 ] (Comp: 0, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ 1 >= Ar_0 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ Fresh_0 >= 1 ] (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ Ar_0 >= 2 ] (Comp: 1, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Applied AI with 'oct' on problem 5 to obtain the following invariants: For symbol f4: -X_3 + 2 >= 0 /\ X_1 - X_3 >= 0 /\ X_3 - 2 >= 0 /\ X_1 + X_3 - 4 >= 0 /\ X_1 - 2 >= 0 For symbol f5: -X_3 + 2 >= 0 /\ X_2 - X_3 + 1 >= 0 /\ -X_2 - X_3 + 3 >= 0 /\ X_1 - X_3 >= 0 /\ X_3 - 2 >= 0 /\ X_2 + X_3 - 3 >= 0 /\ -X_2 + X_3 - 1 >= 0 /\ X_1 + X_3 - 4 >= 0 /\ -X_2 + 1 >= 0 /\ X_1 - X_2 - 1 >= 0 /\ X_2 - 1 >= 0 /\ X_1 + X_2 - 3 >= 0 /\ X_1 - 2 >= 0 This yielded the following problem: 6: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] (Comp: 1, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ -Ar_2 + 2 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ Ar_0 - 2 >= 0 /\ Ar_0 >= 2 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ -Ar_2 + 2 >= 0 /\ Ar_1 - Ar_2 + 1 >= 0 /\ -Ar_1 - Ar_2 + 3 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_1 + Ar_2 - 3 >= 0 /\ -Ar_1 + Ar_2 - 1 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ -Ar_1 + 1 >= 0 /\ Ar_0 - Ar_1 - 1 >= 0 /\ Ar_1 - 1 >= 0 /\ Ar_0 + Ar_1 - 3 >= 0 /\ Ar_0 - 2 >= 0 /\ Fresh_0 >= 1 ] (Comp: 0, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ -Ar_2 + 2 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ Ar_0 - 2 >= 0 /\ 1 >= Ar_0 ] (Comp: 1, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ -Ar_2 + 2 >= 0 /\ Ar_1 - Ar_2 + 1 >= 0 /\ -Ar_1 - Ar_2 + 3 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_1 + Ar_2 - 3 >= 0 /\ -Ar_1 + Ar_2 - 1 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ -Ar_1 + 1 >= 0 /\ Ar_0 - Ar_1 - 1 >= 0 /\ Ar_1 - 1 >= 0 /\ Ar_0 + Ar_1 - 3 >= 0 /\ Ar_0 - 2 >= 0 /\ 0 >= Ar_1 ] start location: koat_start leaf cost: 0 Testing for unsatisfiable constraints removes the following transitions from problem 6: f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 0, Ar_2, Ar_3, Ar_4)) [ -Ar_2 + 2 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ Ar_0 - 2 >= 0 /\ 1 >= Ar_0 ] f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f3(Ar_0, Ar_1, Ar_2, Ar_3, 0)) [ -Ar_2 + 2 >= 0 /\ Ar_1 - Ar_2 + 1 >= 0 /\ -Ar_1 - Ar_2 + 3 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_1 + Ar_2 - 3 >= 0 /\ -Ar_1 + Ar_2 - 1 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ -Ar_1 + 1 >= 0 /\ Ar_0 - Ar_1 - 1 >= 0 /\ Ar_1 - 1 >= 0 /\ Ar_0 + Ar_1 - 3 >= 0 /\ Ar_0 - 2 >= 0 /\ 0 >= Ar_1 ] We thus obtain the following problem: 7: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] (Comp: 1, Cost: 1) f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(2, Ar_1, 2, Fresh_2, Ar_4)) (Comp: ?, Cost: 1) f4(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f5(Ar_0, 1, Ar_2, Ar_3, Ar_4)) [ -Ar_2 + 2 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ Ar_0 - 2 >= 0 /\ Ar_0 >= 2 ] (Comp: ?, Cost: 1) f5(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f4(Ar_0 + 1, Ar_1, Ar_2, Fresh_0, Ar_4)) [ -Ar_2 + 2 >= 0 /\ Ar_1 - Ar_2 + 1 >= 0 /\ -Ar_1 - Ar_2 + 3 >= 0 /\ Ar_0 - Ar_2 >= 0 /\ Ar_2 - 2 >= 0 /\ Ar_1 + Ar_2 - 3 >= 0 /\ -Ar_1 + Ar_2 - 1 >= 0 /\ Ar_0 + Ar_2 - 4 >= 0 /\ -Ar_1 + 1 >= 0 /\ Ar_0 - Ar_1 - 1 >= 0 /\ Ar_1 - 1 >= 0 /\ Ar_0 + Ar_1 - 3 >= 0 /\ Ar_0 - 2 >= 0 /\ Fresh_0 >= 1 ] start location: koat_start leaf cost: 0 Complexity upper bound ? Time: 1.804 sec (SMT: 1.738 sec)