Apache OpenOffice (AOO) Bugzilla – Issue 124115
Solver does not identify a linear model as infeasible
Last modified: 2014-01-31 17:33:58 UTC
Created attachment 82400 [details] spreadsheet that replicates the problem The linear programming Solver is giving nonsense results for some infeasible problems. An attached example is: Min A2 = 10 + 0.03 * B2 + 0.5625 * C2 s.t. B2 >= 0 C2 >= 0 D2 = 1.5 * B2 - 9.81 * A2 >= 0 E2 = A2 - 4 * (A2 - 0.5 * C2) >= 0 In OpenOffice 3.3.0 or 3.2.1, the Solver recognizes this problem as infeasible. However in 4.0.1, it is reporting success with B2 = 0, C2 = 96, D2 = -627.84, E2 = 0. This violates the D2 constraint, so should not have been reported as a successful solution. I don't know when https://issues.apache.org/ooo/show_bug.cgi?id=118160 went into a release, but my guess is this problem is related to having changed the linear solver. As it happens I am a contributor to several COIN-OR projects, I'm quite familiar with those solvers so if the LP as sent from Calc to CoinMP looks correct I can help look into what's happening on the solver side.
A2=3908 with AOO410m1(Build:9750) - Rev. 1557669 2014-01-14_04:11:13 - Rev. 1557927 Debian Gnumeric 1.12.9 gives error.
Created attachment 82401 [details] screenshot of spreadsheet
I also get the same A2 = 3908.69 "solution" when I enter B2 >= 0 and C2 >= 0 as separate constraints. The A2 = 64, B2 = 0, C2 = 96 result was from selecting the "Assume variables as non-negative" option, with the only explicit constraints on D2 >= 0 and E2 >= 0.