MAYBE

Initial complexity problem:
1:	T:
		(?, 1)    f10(a, b, c, d, e, f) -> f16(a, 0, g, g, e, f) [ 0 >= a ]
		(?, 1)    f16(a, b, c, d, e, f) -> f16(a, b, c, d, e, f) [ d >= 1 ]
		(?, 1)    f25(a, b, c, d, e, f) -> f25(a, b, c, d, e, f)
		(?, 1)    f27(a, b, c, d, e, f) -> f30(a, b, c, d, e, f)
		(?, 1)    f16(a, b, c, d, e, f) -> f10(g, b, c, d, 0, g) [ 0 >= d ]
		(?, 1)    f10(a, b, c, d, e, f) -> f25(a, b, c, d, e, f) [ a >= 1 ]
		(1, 1)    f0(a, b, c, d, e, f) -> f10(g, 0, c, d, 0, g)
	start location:	f0
	leaf cost:	0

Slicing away variables that do not contribute to conditions from problem 1 leaves variables [a, d].
We thus obtain the following problem:
2:	T:
		(1, 1)    f0(a, d) -> f10(g, d)
		(?, 1)    f10(a, d) -> f25(a, d) [ a >= 1 ]
		(?, 1)    f16(a, d) -> f10(g, d) [ 0 >= d ]
		(?, 1)    f27(a, d) -> f30(a, d)
		(?, 1)    f25(a, d) -> f25(a, d)
		(?, 1)    f16(a, d) -> f16(a, d) [ d >= 1 ]
		(?, 1)    f10(a, d) -> f16(a, g) [ 0 >= a ]
	start location:	f0
	leaf cost:	0

Repeatedly removing leaves of the complexity graph in problem 2 produces the following problem:
3:	T:
		(1, 1)    f0(a, d) -> f10(g, d)
		(?, 1)    f10(a, d) -> f25(a, d) [ a >= 1 ]
		(?, 1)    f16(a, d) -> f10(g, d) [ 0 >= d ]
		(?, 1)    f25(a, d) -> f25(a, d)
		(?, 1)    f16(a, d) -> f16(a, d) [ d >= 1 ]
		(?, 1)    f10(a, d) -> f16(a, g) [ 0 >= a ]
	start location:	f0
	leaf cost:	1

A polynomial rank function with
	Pol(f0) = 1
	Pol(f10) = 1
	Pol(f25) = 0
	Pol(f16) = 1
orients all transitions weakly and the transition
	f10(a, d) -> f25(a, d) [ a >= 1 ]
strictly and produces the following problem:
4:	T:
		(1, 1)    f0(a, d) -> f10(g, d)
		(1, 1)    f10(a, d) -> f25(a, d) [ a >= 1 ]
		(?, 1)    f16(a, d) -> f10(g, d) [ 0 >= d ]
		(?, 1)    f25(a, d) -> f25(a, d)
		(?, 1)    f16(a, d) -> f16(a, d) [ d >= 1 ]
		(?, 1)    f10(a, d) -> f16(a, g) [ 0 >= a ]
	start location:	f0
	leaf cost:	1

Applied AI with 'oct' on problem 4 to obtain the following invariants:
  For symbol f16: -X_1 >= 0
  For symbol f25: X_1 - 1 >= 0


This yielded the following problem:
5:	T:
		(?, 1)    f10(a, d) -> f16(a, g) [ 0 >= a ]
		(?, 1)    f16(a, d) -> f16(a, d) [ -a >= 0 /\ d >= 1 ]
		(?, 1)    f25(a, d) -> f25(a, d) [ a - 1 >= 0 ]
		(?, 1)    f16(a, d) -> f10(g, d) [ -a >= 0 /\ 0 >= d ]
		(1, 1)    f10(a, d) -> f25(a, d) [ a >= 1 ]
		(1, 1)    f0(a, d) -> f10(g, d)
	start location:	f0
	leaf cost:	1

By chaining the transition f10(a, d) -> f25(a, d) [ a >= 1 ] with all transitions in problem 5, the following new transition is obtained:
	f10(a, d) -> f25(a, d) [ a >= 1 /\ a - 1 >= 0 ]
We thus obtain the following problem:
6:	T:
		(1, 2)    f10(a, d) -> f25(a, d) [ a >= 1 /\ a - 1 >= 0 ]
		(?, 1)    f10(a, d) -> f16(a, g) [ 0 >= a ]
		(?, 1)    f16(a, d) -> f16(a, d) [ -a >= 0 /\ d >= 1 ]
		(?, 1)    f25(a, d) -> f25(a, d) [ a - 1 >= 0 ]
		(?, 1)    f16(a, d) -> f10(g, d) [ -a >= 0 /\ 0 >= d ]
		(1, 1)    f0(a, d) -> f10(g, d)
	start location:	f0
	leaf cost:	1

Complexity upper bound ?

Time: 0.289 sec (SMT: 0.270 sec)