Global consistency problem.

Hi,

I wrote a small program as following:

########################################
:-lib(ic).

case5(LD1,LD2,Va):-
LD1 = [X1,X2,X3,X4],
LD2 = [D1,D2],
LD1 :: [0.0.. 20.0],
LD2 :: [1.0.. 12.0],
Va :: 0.0 .. 5.0,
ic:(X1 =:= 0),
ic:(X2 =< X1+4),
ic:(X2 >= X1+2),
ic:(X3 =:= X1+D1),
ic:(X4 =:= X2+D2),
ic:(D1 =< D2+Va),
ic:(D1 >= D2-Va),
ic:(X4 =< X3).
###################################

I got result:
LD1 = [0, X2{2.0 .. 4.0}, X3{3.0 .. 12.0}, X4{3.0 .. 12.0}]
LD2 = [X3{3.0 .. 12.0}, D2{1.0 .. 10.0}]
Va = Va{0.0 .. 5.0}

It seems the result is incorrect (e.g. When Va=0, there exists no
solution). I guess it is a problem of global consistency, since there are
several constraints with three variables. 

I have tried using xpress, but it does not help.
What should I do if I want global consistency with several constraints? Is
there anything I can use if I change the CSP problem to integer domain?

Thanks
Xiaohua

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Xiaohua Kong                    __ O_     Off. : (514)398-3937
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