Re: [Help-glpk] logical operators

[Michael Hennebry]

On Wed, 12 Aug 2009, Yaron Kretchmer wrote:

> a,b,c are binary variables.
>
> I want c to be 1 if and only if a=b=1.  What Big-M forumlation do I need?

c <= a, b
c >= a + b - 1
c >= 0

Note that with a and b binary,
the above four constraints make c binary.
One could, if one wanted, omit c's integrality and <=1 constraints.
Whether that is a good idea depends on the algorithm of the solver.

--
Michael   address@hidden
"Pessimist: The glass is half empty.
Optimist:   The glass is half full.
Engineer:   The glass is twice as big as it needs to be."