MAYBE Initial complexity problem: 1: T: (Comp: ?, Cost: 1) f14(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f14(Ar_0 - 1, Ar_1 - 1, Ar_2 + 1, Fresh_3, Ar_4, Ar_5, Ar_6)) [ Ar_0 >= 1 /\ Fresh_3 >= 1 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f14(Ar_0 - 1, Ar_1, Ar_2, Fresh_2, Ar_4, Ar_5, Ar_6)) [ 0 >= Fresh_2 /\ Ar_0 >= 1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f24(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f24(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6)) (Comp: ?, Cost: 1) f26(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f29(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6)) (Comp: ?, Cost: 1) f14(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f24(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6)) [ 0 >= Ar_0 ] (Comp: ?, Cost: 1) f0(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f14(2*Fresh_0 + 1, Fresh_1, 0, Ar_3, Fresh_1, 2*Fresh_0 + 1, Fresh_0)) [ Fresh_1 >= 1 /\ 2*Fresh_0 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6) -> Com_1(f0(Ar_0, Ar_1, Ar_2, Ar_3, Ar_4, Ar_5, Ar_6)) [ 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(f0(Ar_0, Ar_1)) [ 0 <= 0 ] (Comp: ?, Cost: 1) f0(Ar_0, Ar_1) -> Com_1(f14(2*Fresh_0 + 1, Fresh_1)) [ Fresh_1 >= 1 /\ 2*Fresh_0 >= 0 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ 0 >= Ar_0 ] (Comp: ?, Cost: 1) f26(Ar_0, Ar_1) -> Com_1(f29(Ar_0, Ar_1)) (Comp: ?, Cost: 1) f24(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1)) [ 0 >= Fresh_2 /\ Ar_0 >= 1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1 - 1)) [ Ar_0 >= 1 /\ Fresh_3 >= 1 ] start location: koat_start leaf cost: 0 Testing for reachability in the complexity graph removes the following transition from problem 2: f26(Ar_0, Ar_1) -> Com_1(f29(Ar_0, Ar_1)) We thus obtain the following problem: 3: T: (Comp: ?, Cost: 1) f24(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ 0 >= Ar_0 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1 - 1)) [ Ar_0 >= 1 /\ Fresh_3 >= 1 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1)) [ 0 >= Fresh_2 /\ Ar_0 >= 1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f0(Ar_0, Ar_1) -> Com_1(f14(2*Fresh_0 + 1, Fresh_1)) [ Fresh_1 >= 1 /\ 2*Fresh_0 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f0(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) f24(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ 0 >= Ar_0 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1 - 1)) [ Ar_0 >= 1 /\ Fresh_3 >= 1 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1)) [ 0 >= Fresh_2 /\ Ar_0 >= 1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: 1, Cost: 1) f0(Ar_0, Ar_1) -> Com_1(f14(2*Fresh_0 + 1, Fresh_1)) [ Fresh_1 >= 1 /\ 2*Fresh_0 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f0(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 A polynomial rank function with Pol(f24) = 0 Pol(f14) = 1 Pol(f0) = 1 Pol(koat_start) = 1 orients all transitions weakly and the transition f14(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ 0 >= Ar_0 ] strictly and produces the following problem: 5: T: (Comp: ?, Cost: 1) f24(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) (Comp: 1, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ 0 >= Ar_0 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1 - 1)) [ Ar_0 >= 1 /\ Fresh_3 >= 1 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1)) [ 0 >= Fresh_2 /\ Ar_0 >= 1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: 1, Cost: 1) f0(Ar_0, Ar_1) -> Com_1(f14(2*Fresh_0 + 1, Fresh_1)) [ Fresh_1 >= 1 /\ 2*Fresh_0 >= 0 ] (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f0(Ar_0, Ar_1)) [ 0 <= 0 ] start location: koat_start leaf cost: 0 Applied AI with 'oct' on problem 5 to obtain the following invariants: For symbol f24: -X_1 >= 0 This yielded the following problem: 6: T: (Comp: 1, Cost: 0) koat_start(Ar_0, Ar_1) -> Com_1(f0(Ar_0, Ar_1)) [ 0 <= 0 ] (Comp: 1, Cost: 1) f0(Ar_0, Ar_1) -> Com_1(f14(2*Fresh_0 + 1, Fresh_1)) [ Fresh_1 >= 1 /\ 2*Fresh_0 >= 0 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1)) [ 0 >= Fresh_2 /\ Ar_0 >= 1 /\ Ar_0 >= Ar_1 + 1 ] (Comp: ?, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f14(Ar_0 - 1, Ar_1 - 1)) [ Ar_0 >= 1 /\ Fresh_3 >= 1 ] (Comp: 1, Cost: 1) f14(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ 0 >= Ar_0 ] (Comp: ?, Cost: 1) f24(Ar_0, Ar_1) -> Com_1(f24(Ar_0, Ar_1)) [ -Ar_0 >= 0 ] start location: koat_start leaf cost: 0 Complexity upper bound ? Time: 1.513 sec (SMT: 1.462 sec)