Where can I find the details of the detailed presolve procedure? Thanks
AMPL’s presolve procedure is described in this paper:
Robert Fourer and David M. Gay, Experience with a Primal Presolve Algorithm. In Large Scale Optimization: State of the Art, W.W. Hager, D.W. Hearn and P.M. Pardalos, eds., Kluwer Academic Publishers (Dordrecht, 1994) 135-154.
You might have access to this paper through a university library. If not, you can access a preprint on our website.