
From:  Xiaohua Kong 
Subject:  A qestion (bug?) of FD solver 
Date:  Mon, 24 Mar 2003 13:41:13 0500 
Hi,
I am using FD solver to work on some verification
problem that is modeled as CSP problem. Since most constraints are linear, I
choose partial consistency operators in FD solver.
Here is a small example:
========================
ieq(LD1,LD2,Va):
LD1 = [X1,X2,X3,X4], LD2 = [D1,D2], fd_domain(LD1,0,20), fd_domain(LD2,1,12), Va #=<5, Va #>=0, X1 #= 0, X2 #=< X1+4, X2 #>= X1+2, X3 #= X1+D1, X4 #= X2+D2, D1 #=< D2+Va, D1 #>= D2Va, X4 #=< X3. =========================== By asking ieq(LD1,LD2,Va).
The solver gives answer:
LD1 = [0,_#25(2..4),_#47(3..12),_#69(3..12)]
LD2 = [_#91(3..12),_#113(1..10)] Va = _#134(0..5) However, there is no assignment exsits if Va=0.
Actually, labeling Va will return give answer that
Va could b [2,5].
==============================================
Several questions on this penominon:
 Is there any problem with the code? Or it is a
problem that caused by the algrithm.
 Without labeling, if the solver gives answer
"yes" and return a domain, does that means there exist at least one solution?
(Even though the answer of the variable domains is not accurate).
 The computation cost of labeling.
Thanks
Xiaohua
Kong 
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