MAYBE Initial complexity problem: 1: T: (Comp: ?, Cost: 1) f2(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0, Ar_1, Ar_2, Ar_3)) (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0 + 1, Ar_1, Fresh_5, Ar_3)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0 + 1, Ar_1, Fresh_4, Ar_3)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0, Ar_1, 0, Ar_3)) [ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0 + 1, Ar_0, Fresh_3, Ar_3)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0 + 1, Ar_0, Fresh_2, Ar_3)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f1(Ar_0, Ar_0, 0, Ar_3)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f300(Ar_0, Ar_1, Ar_2, Fresh_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f300(Ar_0, Ar_1, Ar_2, Fresh_0)) [ Ar_0 >= Ar_1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3) -> Com_1(f2(Ar_0, Ar_1, Ar_2, Ar_3)) [ 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_1]. We thus obtain the following problem: 2: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f2(Ar_0, Ar_1)) [ 0 <= 0 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_0)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) [ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) start location: koat_start leaf cost: 0 Testing for reachability in the complexity graph removes the following transition from problem 2: f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_1 >= Ar_0 + 1 ] We thus obtain the following problem: 3: T: (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) [ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_0)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f2(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f2(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Repeatedly propagating knowledge in problem 3 produces the following problem: 4: T: (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) [ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_0)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: 1, Cost: 1) f2(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f2(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f1) = 1 Pol(f300) = 0 Pol(f2) = 1 Pol(koat_start) = 1 orients all transitions weakly and the transition f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] strictly and produces the following problem: 5: T: (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) [ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_0)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: 1, Cost: 1) f2(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f2(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f1) = -V_1 + V_2 + 1 Pol(f300) = -V_1 + V_2 + 1 Pol(f2) = -V_1 + V_2 + 1 Pol(koat_start) = -V_1 + V_2 + 1 orients all transitions weakly and the transitions f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] strictly and produces the following problem: 6: T: (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: Ar_0 + Ar_1 + 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) [ Ar_1 >= Ar_0 + 1 ] (Comp: Ar_0 + Ar_1 + 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: Ar_0 + Ar_1 + 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_0)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: 1, Cost: 1) f2(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f2(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f1) = -V_1 + V_2 Pol(f300) = -V_1 + V_2 Pol(f2) = -V_1 + V_2 Pol(koat_start) = -V_1 + V_2 orients all transitions weakly and the transition f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] strictly and produces the following problem: 7: T: (Comp: Ar_0 + Ar_1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ Fresh_5 >= 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: Ar_0 + Ar_1 + 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_1)) [ 0 >= Fresh_4 + 1 /\ Ar_1 >= Ar_0 + 1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) [ Ar_1 >= Ar_0 + 1 ] (Comp: Ar_0 + Ar_1 + 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ Fresh_3 >= 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: Ar_0 + Ar_1 + 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0 + 1, Ar_0)) [ 0 >= Fresh_2 + 1 /\ Ar_1 >= F /\ Ar_0 = Ar_1 ] (Comp: ?, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_0)) [ Ar_1 >= E /\ Ar_0 = Ar_1 ] (Comp: 1, Cost: 1) f1(Ar_0, Ar_1) -> Com_1(f300(Ar_0, Ar_1)) [ Ar_0 >= Ar_1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: 1, Cost: 1) f2(Ar_0, Ar_1) -> Com_1(f1(Ar_0, Ar_1)) (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f2(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Complexity upper bound ? Time: 1.695 sec (SMT: 1.612 sec)