YES(?, 2 * pow(2, a) * 2 + pow(2, 2 * pow(2, a) * 2 + 2*a + 2) * 2 + 3*a + 7) Initial complexity problem: 1: T: (1, 1) f(a, b, c) -> g(a, 1, 1) (?, 1) g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ] (?, 1) g(a, b, c) -> h(a, b, c) [ a <= 0 ] (?, 1) h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] (?, 1) h(a, b, c) -> i(a, b, c) [ b <= 0 ] (?, 1) i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] start location: f leaf cost: 0 A polynomial rank function with Pol(f) = 2 Pol(g) = 2 Pol(h) = 1 Pol(i) = -1 orients all transitions weakly and the transitions h(a, b, c) -> i(a, b, c) [ b <= 0 ] g(a, b, c) -> h(a, b, c) [ a <= 0 ] strictly and produces the following problem: 2: T: (1, 1) f(a, b, c) -> g(a, 1, 1) (?, 1) g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ] (2, 1) g(a, b, c) -> h(a, b, c) [ a <= 0 ] (?, 1) h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] (2, 1) h(a, b, c) -> i(a, b, c) [ b <= 0 ] (?, 1) i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] start location: f leaf cost: 0 A polynomial rank function with Pol(f) = V_1 Pol(g) = V_1 Pol(h) = V_1 Pol(i) = V_1 + V_2 orients all transitions weakly and the transition g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ] strictly and produces the following problem: 3: T: (1, 1) f(a, b, c) -> g(a, 1, 1) (a, 1) g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ] (2, 1) g(a, b, c) -> h(a, b, c) [ a <= 0 ] (?, 1) h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] (2, 1) h(a, b, c) -> i(a, b, c) [ b <= 0 ] (?, 1) i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] start location: f leaf cost: 0 A polynomial rank function with Pol(i) = V_1 + V_2 + 1 Pol(h) = V_2 and size complexities S("i(a, b, c) -> i(a, b, c - 1) [ c > 0 ]", 0-0) = a S("i(a, b, c) -> i(a, b, c - 1) [ c > 0 ]", 0-1) = pow(2, a) S("i(a, b, c) -> i(a, b, c - 1) [ c > 0 ]", 0-2) = ? S("h(a, b, c) -> i(a, b, c) [ b <= 0 ]", 0-0) = a S("h(a, b, c) -> i(a, b, c) [ b <= 0 ]", 0-1) = pow(2, a) S("h(a, b, c) -> i(a, b, c) [ b <= 0 ]", 0-2) = ? S("h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ]", 0-0) = a S("h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ]", 0-1) = pow(2, a) S("h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ]", 0-2) = ? S("g(a, b, c) -> h(a, b, c) [ a <= 0 ]", 0-0) = a S("g(a, b, c) -> h(a, b, c) [ a <= 0 ]", 0-1) = pow(2, a) S("g(a, b, c) -> h(a, b, c) [ a <= 0 ]", 0-2) = 1 S("g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ]", 0-0) = a S("g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ]", 0-1) = pow(2, a) S("g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ]", 0-2) = 1 S("f(a, b, c) -> g(a, 1, 1)", 0-0) = a S("f(a, b, c) -> g(a, 1, 1)", 0-1) = 1 S("f(a, b, c) -> g(a, 1, 1)", 0-2) = 1 orients the transitions i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] weakly and the transition h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] strictly and produces the following problem: 4: T: (1, 1) f(a, b, c) -> g(a, 1, 1) (a, 1) g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ] (2, 1) g(a, b, c) -> h(a, b, c) [ a <= 0 ] (2 * pow(2, a) * 2 + 2*a + 2, 1) h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] (2, 1) h(a, b, c) -> i(a, b, c) [ b <= 0 ] (?, 1) i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] start location: f leaf cost: 0 A polynomial rank function with Pol(i) = V_3 and size complexities S("i(a, b, c) -> i(a, b, c - 1) [ c > 0 ]", 0-0) = a S("i(a, b, c) -> i(a, b, c - 1) [ c > 0 ]", 0-1) = pow(2, a) S("i(a, b, c) -> i(a, b, c - 1) [ c > 0 ]", 0-2) = pow(2, 2 * pow(2, a) * 2 + 2*a + 2) S("h(a, b, c) -> i(a, b, c) [ b <= 0 ]", 0-0) = a S("h(a, b, c) -> i(a, b, c) [ b <= 0 ]", 0-1) = pow(2, a) S("h(a, b, c) -> i(a, b, c) [ b <= 0 ]", 0-2) = pow(2, 2 * pow(2, a) * 2 + 2*a + 2) S("h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ]", 0-0) = a S("h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ]", 0-1) = pow(2, a) S("h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ]", 0-2) = pow(2, 2 * pow(2, a) * 2 + 2*a + 2) S("g(a, b, c) -> h(a, b, c) [ a <= 0 ]", 0-0) = a S("g(a, b, c) -> h(a, b, c) [ a <= 0 ]", 0-1) = pow(2, a) S("g(a, b, c) -> h(a, b, c) [ a <= 0 ]", 0-2) = 1 S("g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ]", 0-0) = a S("g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ]", 0-1) = pow(2, a) S("g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ]", 0-2) = 1 S("f(a, b, c) -> g(a, 1, 1)", 0-0) = a S("f(a, b, c) -> g(a, 1, 1)", 0-1) = 1 S("f(a, b, c) -> g(a, 1, 1)", 0-2) = 1 orients the transition i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] weakly and the transition i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] strictly and produces the following problem: 5: T: (1, 1) f(a, b, c) -> g(a, 1, 1) (a, 1) g(a, b, c) -> g(a - 1, 2*b, c) [ a > 0 ] (2, 1) g(a, b, c) -> h(a, b, c) [ a <= 0 ] (2 * pow(2, a) * 2 + 2*a + 2, 1) h(a, b, c) -> h(a, b - 1, 2*c) [ b > 0 ] (2, 1) h(a, b, c) -> i(a, b, c) [ b <= 0 ] (pow(2, 2 * pow(2, a) * 2 + 2*a + 2) * 2, 1) i(a, b, c) -> i(a, b, c - 1) [ c > 0 ] start location: f leaf cost: 0 Complexity upper bound 2 * pow(2, a) * 2 + pow(2, 2 * pow(2, a) * 2 + 2*a + 2) * 2 + 3*a + 7 Time: 0.438 sec (SMT: 0.418 sec)