[Help-glpk] Some simple intro questions

[STEVE VESTAL]

I have a couple of initial questions based on skimming the GLPK Reference Manual and examples.

The manual says set_glb_obj_coef applies to structural variables.  How are auxiliary (aka slack, row) variable costs set? 

Are free variables implemented as the difference of two non-negative variables?  Is it possible to set the costs (objective coefficients) of the two to have the same sign so that the absolute value of a free variable can be maximized/minimized?

Has anyone benchmarked GLPK against the netlib LP suite, http://www.netlib.org/lp/

Are there any reports of how it has fared with those?  (The objective values obtained by rational solution have been published.)

Thanks.