MAYBE Initial complexity problem: 1: T: (Comp: ?, Cost: 1) f10(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f16(Ar_0, 0, Fresh_2, Ar_3, Ar_4)) [ 0 >= Ar_0 /\ Fresh_2 >= 1 ] (Comp: ?, Cost: 1) f16(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f16(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ Ar_2 >= 1 ] (Comp: ?, Cost: 1) f25(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f25(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) (Comp: ?, Cost: 1) f27(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f30(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) (Comp: ?, Cost: 1) f16(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f10(Fresh_1, Ar_1, Ar_2, 0, Fresh_1)) [ 0 >= Ar_2 ] (Comp: ?, Cost: 1) f10(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f25(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ Ar_0 >= 1 ] (Comp: ?, Cost: 1) f0(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f10(Fresh_0, 0, Ar_2, 0, Fresh_0)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4) -> Com_1(f0(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Slicing away variables that do not contribute to conditions from problem 1 leaves variables [Ar_0, Ar_2]. We thus obtain the following problem: 2: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_2) -> Com_1(f0(Ar_0, Ar_2)) [ 0 <= 0 ] (Comp: ?, Cost: 1) f0(Ar_0, Ar_2) -> Com_1(f10(Fresh_0, Ar_2)) (Comp: ?, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) [ Ar_0 >= 1 ] (Comp: ?, Cost: 1) f16(Ar_0, Ar_2) -> Com_1(f10(Fresh_1, Ar_2)) [ 0 >= Ar_2 ] (Comp: ?, Cost: 1) f27(Ar_0, Ar_2) -> Com_1(f30(Ar_0, Ar_2)) (Comp: ?, Cost: 1) f25(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) (Comp: ?, Cost: 1) f16(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Ar_2)) [ Ar_2 >= 1 ] (Comp: ?, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Fresh_2)) [ 0 >= Ar_0 /\ Fresh_2 >= 1 ] start location: koat_start leaf cost: 0 Testing for reachability in the complexity graph removes the following transitions from problem 2: f16(Ar_0, Ar_2) -> Com_1(f10(Fresh_1, Ar_2)) [ 0 >= Ar_2 ] f27(Ar_0, Ar_2) -> Com_1(f30(Ar_0, Ar_2)) We thus obtain the following problem: 3: T: (Comp: ?, Cost: 1) f16(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Ar_2)) [ Ar_2 >= 1 ] (Comp: ?, Cost: 1) f25(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) (Comp: ?, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Fresh_2)) [ 0 >= Ar_0 /\ Fresh_2 >= 1 ] (Comp: ?, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) [ Ar_0 >= 1 ] (Comp: ?, Cost: 1) f0(Ar_0, Ar_2) -> Com_1(f10(Fresh_0, Ar_2)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_2) -> Com_1(f0(Ar_0, Ar_2)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Repeatedly propagating knowledge in problem 3 produces the following problem: 4: T: (Comp: ?, Cost: 1) f16(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Ar_2)) [ Ar_2 >= 1 ] (Comp: ?, Cost: 1) f25(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) (Comp: 1, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Fresh_2)) [ 0 >= Ar_0 /\ Fresh_2 >= 1 ] (Comp: 1, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) [ Ar_0 >= 1 ] (Comp: 1, Cost: 1) f0(Ar_0, Ar_2) -> Com_1(f10(Fresh_0, Ar_2)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_2) -> Com_1(f0(Ar_0, Ar_2)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Applied AI with 'oct' on problem 4 to obtain the following invariants: For symbol f16: X_2 - 1 >= 0 /\ -X_1 + X_2 - 1 >= 0 /\ -X_1 >= 0 For symbol f25: X_1 - 1 >= 0 This yielded the following problem: 5: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_2) -> Com_1(f0(Ar_0, Ar_2)) [ 0 <= 0 ] (Comp: 1, Cost: 1) f0(Ar_0, Ar_2) -> Com_1(f10(Fresh_0, Ar_2)) (Comp: 1, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) [ Ar_0 >= 1 ] (Comp: 1, Cost: 1) f10(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Fresh_2)) [ 0 >= Ar_0 /\ Fresh_2 >= 1 ] (Comp: ?, Cost: 1) f25(Ar_0, Ar_2) -> Com_1(f25(Ar_0, Ar_2)) [ Ar_0 - 1 >= 0 ] (Comp: ?, Cost: 1) f16(Ar_0, Ar_2) -> Com_1(f16(Ar_0, Ar_2)) [ Ar_2 - 1 >= 0 /\ -Ar_0 + Ar_2 - 1 >= 0 /\ -Ar_0 >= 0 /\ Ar_2 >= 1 ] start location: koat_start leaf cost: 0 Complexity upper bound ? Time: 0.992 sec (SMT: 0.950 sec)