YES

(format LCTRS :logic QF_LIA)
(fun f1 2 :sort (Int Int Int))
(fun u_5 1 :sort (Int Int))

(rule (u_5 w_2_0) w_2_0 :vars ((w_2_0 Int)))
(rule (f1 i_1 j_2) (u_5 (f1 (- i_1 1) (+ j_2 1))) :guard (distinct i_1 0) :vars ((i_1 Int) (j_2 Int)))
(rule (f1 i_3 j_4) j_4 :guard (= i_3 0) :vars ((i_3 Int) (j_4 Int)))

Confluent by Parallel Closedness with proof:
no critical pairs

Elapsed Time:  13.78 ms