Gabor Retvari wrote: > On Monday 28 July 2008, Markus Pilz wrote: > >> we are working on a tool that utilizes glpk to solve a set of maximum >> and minimum cost flows. So far, our approach looks promising. (This >> implies a big thank-you to glpk team.) >> >> Currently, we have some difficulties with larger decision variables. For >> example, if the variables of a maximisation problem (max flow) are >> limited by values above 1e9, the solution tends to be inexact. >> >> We still can use the solution as a basis for further processing but >> maybe we lack some lp (or glpk) basics to obtain exact values in a wider >> range. > > Wouldn't it be plausible to run GLPK over precise arithmetics? You can do > this by calling lpx_exact instead of lpx_simplex. > Network flow problems tend > to be seriously overconstrained and thus highly degenerate, calling for > numerical instability. An exact solver would solve this issue, for the prize > of being somewhat slower. I mean, *really* slower.
Yes you are right. We already moved to lpx_exact, but it does not help everywhere. Best regards Markus > > Best regards, > Gabor > > ---- > > http://qosip.tmit.bme.hu/~retvari > > > _______________________________________________ > Help-glpk mailing list > [email protected] > http://lists.gnu.org/mailman/listinfo/help-glpk _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
