Priority
0	1	+1	# priority      
0	1	+1	# load_balancing
4	4	+1	# nb_grp                 
4	4	*4	# nb_elt         [0] [nb_grp]
1	1	*4	# nb_elt         [1] [nb_grp]
16	16	*4	# nb_elt         [2] [nb_grp]
2	2	*4	# nb_elt         [3] [nb_grp]
1	4	+1	# nb_grp_select