Hello Andrew,
when running glp_simplex on the problem, I get this output:
GLPK Simplex Optimizer, v4.47
45 rows, 5 columns, 123 non-zeros
0: obj = 5.000000000e+00 infeas = 3.750e+01 (0)
37: obj = 1.400000000e+01 infeas = 8.833e+00 (0)
PROBLEM HAS NO FEASIBLE SOLUTIONI then used John's coding to write the appended file in CPLEX format. glpsol --lp test.lp leads to the following error in the presolver: Preprocessing... Assertion failed: q->lb < q->ub Error detected in file ..\src\glpnpp03.c at line 556 I would not have expected such an error. @John: Please, check your problem formulation. Best regards Xypron > -------- Forwarded Message -------- > To: [email protected] <[email protected]> > Subject: preprocessing goes into infinite loop > Date: Fri, 13 Jan 2012 17:28:32 -0600 > > Hello! > > I work with the Sage computer algebra system, which can use GLPK as a > backend to solve mixed integer linear programs. Unfortunately, Sage sometimes > crashes when I am trying to solve some linear systems that are > machine-generated for a problem of interest to me. > > I managed to reproduce one of these problems directly in GLPK, linking via > C++. I have placed a copy of the program at > > www.math.usm.edu/perry/glpk_bug.cpp > > The problem creates an LP w/45 rows and 5 columns that apparently sends > GLPK's preprocessing into an infinite loop. If the 45th row is not added > (comment out the BOOM macro at the beginning of the file) then the LP finds a > solution. > > We believe this is a bug in GLPK. If it is a problem with how we are > accessing GLPK from Sage, please let us know. > > Thank you for your attention to this! > > regards > john perry > > > > > _______________________________________________ > Bug-glpk mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/bug-glpk -- Follow me at http://twitter.com/#!/xypron NEU: FreePhone - 0ct/min Handyspartarif mit Geld-zurück-Garantie! Jetzt informieren: http://www.gmx.net/de/go/freephone
test.lp
Description: Binary data
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