Re: [Help-glpk] if-then constrains

[Philip Warner]

At 04:32 PM 1/06/2005, F. Javier Diego Martín wrote:
> For example: if X1+X2>= 10 then X3+X4<=25

One way, not sure it's the best:

    Define S = (X1+X2 - 10)/M, where M is fixed and large enough to ensure 
S <= 1
    Define x in {0,1} (ie. binary integer)
    Constrain x >= S, so x will be 1 if X1+X2 > 10
    Constrain X3+X4 + (x-1)*Q <= 25 where Q is fixed and large enough for 
X3+X4-Q <=25 always




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