My first thought on such a task is to fix all variablee, structural and otherwise, with nonzero reduced costs. Unless using exact arithmetic, that is an interesting task in itself. Even so, I'd expect it to be better than using a single linear constraint to implicitly fix them.
A better tactic might be to take a step back to the reason you want them. -- Michael [email protected] "I was just thinking about the life of a pumpkin. Grow up in the sun, happily entwined with others, and then someone comes along, cuts you open, and rips your guts out." -- Buffy
