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I am interested in the upper bound of the number of inequalities to describe the integer hull of a polyhedron. That is, given an integer programming problem with n inequalities which construct a polyhedron P, we often adding some inequalities to get the integer hull P_I of P. Then what is the maximum number of inequalities needed to describe this P_I? I have known that there are some conclusions on this topic but I don't what they are. I need some paper about it. Please tell me if you know it.

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  • $\begingroup$ If there is no such bound on general integer programming problem, how about 0-1 integer programming? Is there any bound on the number of inequalities to define the Integer hull of 0-1 integer programming problem? $\endgroup$ – THULeiZhixian Apr 12 '14 at 0:59
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Via Rubin:

There is a sequence of polytopes $\{ P_k\}_k$ each defined by two variables and one constraint (plus two nonnegativity constraints) such that the integer hull of $P_k$ has $k+3$ vertices and $k+3$ facets.

$P_k=\{ (x,y)\in \mathbb{R}^2_+ ~|~f_{2k} x + f_{2k+1}y \le f^2_{2k+1}-1\}$

Here, $f_j$ is the $j$-th Fibonacci number.

This shows that the number of facets of the integer hull $P_I$ cannot be bounded above in terms of the number variables and constraints of $P$.

Schrijver provides a nice collection of these kind of results in his Theory of Linear and Integer Programming.

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