Thank you for your response. One reason is debugging. I generate the LP problems by linearizing nonlinear problems. A redundant nonlinear constraint may or may not be nonredundant in the LP problem after linearization. Identifying redundant rows / columns could help me debugging the nonlinear part. Another reason is numerical stability and performance issues.
What do you advise? Thank you, Ali On Jan 10, 2008 3:35 PM, Andrew Makhorin <[EMAIL PROTECTED]> wrote: > > Is there a way to get information from the presolve routines why > > certain rows / columns can be eliminated from the model? > > > My LP problems only have continuous variables. > > The lp presolver (see the module glplpp) keeps all information about > applied transformations in an internal stack, however, this information > is not intended to be used out of the lp presolver. Besides, it would be > problematic to analyze it adequately due to its derivative nature. For > example, some column may be eliminated, because other column in the same > row was fixed by its reduced costs obtained from other row that made the > former column an implied slack variable; i.e. there may not be a clear > reason why this or that column has been removed. > > For which purpose do you need to obtain such information? > > _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
