MAYBE Initial complexity problem: 1: T: (Comp: ?, Cost: 1) f0(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1, Ar_2)) [ Ar_0 >= 0 /\ Ar_1 >= Ar_2 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0 - 1, Ar_1, Ar_2 - 1)) [ Ar_0 >= 1 /\ Ar_1 + 1 >= Ar_2 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1 + Ar_2 - 1, Ar_2 - 1)) [ Ar_0 >= 0 /\ Ar_1 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2) -> Com_1(f0(Ar_0, Ar_1, Ar_2)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Repeatedly propagating knowledge in problem 1 produces the following problem: 2: T: (Comp: 1, Cost: 1) f0(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1, Ar_2)) [ Ar_0 >= 0 /\ Ar_1 >= Ar_2 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0 - 1, Ar_1, Ar_2 - 1)) [ Ar_0 >= 1 /\ Ar_1 + 1 >= Ar_2 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1 + Ar_2 - 1, Ar_2 - 1)) [ Ar_0 >= 0 /\ Ar_1 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2) -> Com_1(f0(Ar_0, Ar_1, Ar_2)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f0) = V_1 Pol(f2) = V_1 Pol(koat_start) = V_1 orients all transitions weakly and the transition f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0 - 1, Ar_1, Ar_2 - 1)) [ Ar_0 >= 1 /\ Ar_1 + 1 >= Ar_2 ] strictly and produces the following problem: 3: T: (Comp: 1, Cost: 1) f0(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1, Ar_2)) [ Ar_0 >= 0 /\ Ar_1 >= Ar_2 ] (Comp: Ar_0, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0 - 1, Ar_1, Ar_2 - 1)) [ Ar_0 >= 1 /\ Ar_1 + 1 >= Ar_2 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1 + Ar_2 - 1, Ar_2 - 1)) [ Ar_0 >= 0 /\ Ar_1 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2) -> Com_1(f0(Ar_0, Ar_1, Ar_2)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Applied AI with 'oct' on problem 3 to obtain the following invariants: For symbol f2: X_2 - X_3 >= 0 /\ X_1 >= 0 This yielded the following problem: 4: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2) -> Com_1(f0(Ar_0, Ar_1, Ar_2)) [ 0 <= 0 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1 + Ar_2 - 1, Ar_2 - 1)) [ Ar_1 - Ar_2 >= 0 /\ Ar_0 >= 0 /\ Ar_1 >= 0 ] (Comp: Ar_0, Cost: 1) f2(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0 - 1, Ar_1, Ar_2 - 1)) [ Ar_1 - Ar_2 >= 0 /\ Ar_0 >= 0 /\ Ar_0 >= 1 /\ Ar_1 + 1 >= Ar_2 ] (Comp: 1, Cost: 1) f0(Ar_0, Ar_1, Ar_2) -> Com_1(f2(Ar_0, Ar_1, Ar_2)) [ Ar_0 >= 0 /\ Ar_1 >= Ar_2 ] start location: koat_start leaf cost: 0 Complexity upper bound ? Time: 1.855 sec (SMT: 1.800 sec)