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## A qestion (bug?) of FD solver

 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 #>= D2-Va,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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