YES(?, 10*a + 2*a^2 + 9) Initial complexity problem: 1: T: (?, 1) eval1(a, b) -> eval2(a, 1) [ a >= 0 ] (?, 1) eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\ b >= 1 /\ a >= b + 1 ] (?, 1) eval2(a, b) -> eval1(a - 1, b) [ a >= 0 /\ b >= 1 /\ b >= a ] (1, 1) start(a, b) -> eval1(a, b) start location: start leaf cost: 0 A polynomial rank function with Pol(eval1) = 2*V_1 + 2 Pol(eval2) = 2*V_1 + 1 Pol(start) = 2*V_1 + 2 orients all transitions weakly and the transitions eval2(a, b) -> eval1(a - 1, b) [ a >= 0 /\ b >= 1 /\ b >= a ] eval1(a, b) -> eval2(a, 1) [ a >= 0 ] strictly and produces the following problem: 2: T: (2*a + 2, 1) eval1(a, b) -> eval2(a, 1) [ a >= 0 ] (?, 1) eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\ b >= 1 /\ a >= b + 1 ] (2*a + 2, 1) eval2(a, b) -> eval1(a - 1, b) [ a >= 0 /\ b >= 1 /\ b >= a ] (1, 1) start(a, b) -> eval1(a, b) start location: start leaf cost: 0 A polynomial rank function with Pol(eval2) = V_1 - V_2 and size complexities S("start(a, b) -> eval1(a, b)", 0-0) = a S("start(a, b) -> eval1(a, b)", 0-1) = b S("eval2(a, b) -> eval1(a - 1, b) [ a >= 0 /\\ b >= 1 /\\ b >= a ]", 0-0) = a + 1 S("eval2(a, b) -> eval1(a - 1, b) [ a >= 0 /\\ b >= 1 /\\ b >= a ]", 0-1) = ? S("eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\\ b >= 1 /\\ a >= b + 1 ]", 0-0) = a + 1 S("eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\\ b >= 1 /\\ a >= b + 1 ]", 0-1) = ? S("eval1(a, b) -> eval2(a, 1) [ a >= 0 ]", 0-0) = a + 1 S("eval1(a, b) -> eval2(a, 1) [ a >= 0 ]", 0-1) = 1 orients the transition eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\ b >= 1 /\ a >= b + 1 ] weakly and the transition eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\ b >= 1 /\ a >= b + 1 ] strictly and produces the following problem: 3: T: (2*a + 2, 1) eval1(a, b) -> eval2(a, 1) [ a >= 0 ] (2*a^2 + 6*a + 4, 1) eval2(a, b) -> eval2(a, 2*b) [ a >= 0 /\ b >= 1 /\ a >= b + 1 ] (2*a + 2, 1) eval2(a, b) -> eval1(a - 1, b) [ a >= 0 /\ b >= 1 /\ b >= a ] (1, 1) start(a, b) -> eval1(a, b) start location: start leaf cost: 0 Complexity upper bound 10*a + 2*a^2 + 9 Time: 0.180 sec (SMT: 0.170 sec)