Re: [Help-glpk] SOS1/SOS2 in GLPK?

[Andrew Makhorin]

> At work i encounter a lot of "SOS #39; type problems - mostly when
> i want to model "choose exactly one member of a group". Currently I
> model this with binary variables, whose sum i constraint to be less
> than 1. Modeling this using SOS seems like a better approach- more
> compact, and also could yield better MIP results. 
> Are SOS #39;s supported in glpk?

SOS1/SOS2 constraints are not supported in glpk directly. However, you
can model them using binary variables. See, for example:
http://lists.gnu.org/archive/html/help-glpk/2007-06/msg00005.html

>  If not, any reason why?

Constraints like SOS1, SOS2 (as well as alldifferent, for example) are
peculiar to constraint programming, not to MIP.