-------- Forwarded Message -------- From: Brendan McKay <[email protected]> To: [email protected] Subject: Using glp_exact() after glp_simplex() has timed out Date: Mon, 5 Jun 2017 16:50:18 +1000
Hi, I use the exact solver for my work in combinatorics and find it very efficient for my problems (tens to hundreds of thousands of variables but only a few dozen constraints). GLPK 4.61 running on Ubuntu 14.04.5 LTS. As recommended in the manual, I call glp_simplex() first and then call glp_exact(), which usually gives a nice speedup. It set an iteration limit for glp_simplex() because sometimes it cycles. However, if the call to glp_simplex() returns due the number of iterations being exceeded (return GLP_EITLIM), sometimes glp_exact() then runs forever. I get a never-ending sequence of outputs like this: 26194: infsum = 144 (33) 26406: infsum = 144 (33) 26619: infsum = 144 (33) 26831: infsum = 144 (33) 27044: infsum = 144 (33) 27257: infsum = 144 (33) 27469: infsum = 144 (33) I infer that glp_simplex() is leaving things in a state unsuitable for starting glp_exact(). In such a case it would be enough to force glp_exact() to begin with a blank slate rather than using the left-overs from a timed-out glp_simplex(). But how can I achieve that short of reconstructing the problem or keeping a copy? Thanks, Brendan. _______________________________________________ Help-glpk mailing list [email protected] https://lists.gnu.org/mailman/listinfo/help-glpk
