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## Re: [Help-glpk] if-then constrains

**From**: |
Philip Warner |

**Subject**: |
Re: [Help-glpk] if-then constrains |

**Date**: |
Wed, 01 Jun 2005 17:20:52 +1000 |

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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`and from pgp.mit.edu:11371 |/
``
`