A simple sample

[address@hidden]

Hello, 

I'm using GNU Prolog for my research. But there some problem with my program, 
which puzzled me for a long time. Here is the source code of my program, after 
compiled to executable file, the result is " user directive failed". Can anyone 
help me locate the error in my program? Thanks!

q(OUTPUTS):-
 get_fd_labeling(Lab),
 statistics(runtime, _),
 temp(Lab,INPUTS,OUTPUTS),
 statistics(runtime, [_,Y]),
 write(OUTPUTS), nl,
 write(INPUTS), nl,
 write('time: '), write(Y), nl.

/*----------- Model definition -----------*/

temp(Lab, INPUTS, OUTPUTS):-
 OUTPUTS = [out],
 INPUTS = [a, b],

 /*---- Domains for integers ----*/
 fd_domain(a, 0, 1),
 fd_domain(b, 0, 1),
 fd_domain(out, 0, 1),
 
 out #<=> a #= b,
 
 lab(Lab, INPUTS).

/*----------- End of model definition -----------*/

lab(normal,L):-
        fd_labeling(L).

lab(ff,L):-
        fd_labelingff(L).

get_fd_labeling(Lab):-
        argument_counter(C),
        get_labeling1(C,Lab).

get_labeling1(1,normal).

get_labeling1(2,Lab):-
        argument_value(1,Lab).

:-initialization(q([1])).