YES(?, 4*a + 4*b + 6)

Initial complexity problem:
1:	T:
		(1, 1)    evalfstart(a, b) -> evalfentryin(a, b)
		(?, 1)    evalfentryin(a, b) -> evalfbb1in(b, a)
		(?, 1)    evalfbb1in(a, b) -> evalfbbin(a, b) [ a >= b ]
		(?, 1)    evalfbb1in(a, b) -> evalfreturnin(a, b) [ b >= a + 1 ]
		(?, 1)    evalfbbin(a, b) -> evalfbb1in(a, b + 1)
		(?, 1)    evalfreturnin(a, b) -> evalfstop(a, b)
	start location:	evalfstart
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 1 produces the following problem:
2:	T:
		(1, 1)    evalfstart(a, b) -> evalfentryin(a, b)
		(?, 1)    evalfentryin(a, b) -> evalfbb1in(b, a)
		(?, 1)    evalfbb1in(a, b) -> evalfbbin(a, b) [ a >= b ]
		(?, 1)    evalfbbin(a, b) -> evalfbb1in(a, b + 1)
	start location:	evalfstart
	leaf cost:	2

Repeatedly propagating knowledge in problem 2 produces the following problem:
3:	T:
		(1, 1)    evalfstart(a, b) -> evalfentryin(a, b)
		(1, 1)    evalfentryin(a, b) -> evalfbb1in(b, a)
		(?, 1)    evalfbb1in(a, b) -> evalfbbin(a, b) [ a >= b ]
		(?, 1)    evalfbbin(a, b) -> evalfbb1in(a, b + 1)
	start location:	evalfstart
	leaf cost:	2

A polynomial rank function with
	Pol(evalfstart) = -2*V_1 + 2*V_2 + 1
	Pol(evalfentryin) = -2*V_1 + 2*V_2 + 1
	Pol(evalfbb1in) = 2*V_1 - 2*V_2 + 1
	Pol(evalfbbin) = 2*V_1 - 2*V_2
orients all transitions weakly and the transition
	evalfbb1in(a, b) -> evalfbbin(a, b) [ a >= b ]
strictly and produces the following problem:
4:	T:
		(1, 1)                evalfstart(a, b) -> evalfentryin(a, b)
		(1, 1)                evalfentryin(a, b) -> evalfbb1in(b, a)
		(2*a + 2*b + 1, 1)    evalfbb1in(a, b) -> evalfbbin(a, b) [ a >= b ]
		(?, 1)                evalfbbin(a, b) -> evalfbb1in(a, b + 1)
	start location:	evalfstart
	leaf cost:	2

Repeatedly propagating knowledge in problem 4 produces the following problem:
5:	T:
		(1, 1)                evalfstart(a, b) -> evalfentryin(a, b)
		(1, 1)                evalfentryin(a, b) -> evalfbb1in(b, a)
		(2*a + 2*b + 1, 1)    evalfbb1in(a, b) -> evalfbbin(a, b) [ a >= b ]
		(2*a + 2*b + 1, 1)    evalfbbin(a, b) -> evalfbb1in(a, b + 1)
	start location:	evalfstart
	leaf cost:	2

Complexity upper bound 4*a + 4*b + 6

Time: 0.083 sec (SMT: 0.079 sec)