Hi, I am using GLPK with matlab (with the glpkmex extension) and I found a bug. Please extract the attached tarball and run glpk_fail_example.m in Matlab (you need glpkmex, the interface to Matlab). It is a simple routing optimization. The first plot shows the possible links between nodes and the numbers (in blue) on the links show the capacity in Mbps. The flows are 18Mbps so the routes cannot use the links with 12Mbps capacity. This translates to an upper bound constraint in GLPK. I solve the problem with both GLPK and Matlab's 'bintprog'. The bintprog gives the right solution (last 3 plots) while the solution given by GLPK (plots 2, 3 and 4) do use the links with 12 Mbps capacity, which means the UB constaint is violated. This is also detected by the lines 42--45 of solve_opt.m. The warning is executed if the ub constraint is violated, and the exit status of glpk is 5.
I don't know if this is a problem of GLPK or glpkmex, but since glpkmex is just a Matlab interface to GLPK and it is GLPK who is performing the optimization, I thought this is probably GLPK's bug. Best, Ali Ercan. -- +++++++++++++++++++++++++++++++++++ Ali Ozer Ercan Post Doctoral Researcher Berkeley Wireless Research Center 2108 Allston Way, Suite 200 Berkeley, CA 94704-1302 USA http://www.eecs.berkeley.edu/~aliercan +++++++++++++++++++++++++++++++++++
glpk_fail_example.tar.gz
Description: GNU Zip compressed data
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