sci.op-research

Matkov writes:

> I have next Integer Linear Programming Constraint Problem:
>
> is it possible to make LP constraint from next function:
>
>
> Y=0 if X=0
> Y=1 if X>0
>
> where X>=0 and X is integer
> Y is also integer

Y <= 1,
X - Y >= 0,
Y >= X/m where m is an an upper bound on X

It can't be done with linear constraints unless you know an upper
bound on X, since (1,0) is in the closed convex hull of
{(0,0)} union {(x,0): x a positive integer}.
--
Robert Israel israel@math.MyUniversitysInitials.ca
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada