Problematic instance

[tkralphs]

The attached instance causes problems for SYMPHONY, even though it is small and has small integer coefficients.

water.txt

With SHA fc6e148, SYMPHONY gets different results depending on parameters, as follows.

./symphony -L water.lp 
Solution Found: Node 0, Level 0
Solution Cost: -95.0000000000
./symphony -L water.lp -v 3 -a 0 #just turn off heuristics
Solution Found: Node 0, Level 0
Solution Cost: -95.0000000000
./symphony -L water.lp -v 3 -e -1 -a 0 #turn off pre-processor and heuristics -- weird
The problem is infeasible!
No Solution Found
./symphony -L water.lp -v 3 -e -1 -a 0 -j 0 #also turn off cuts, it's fine again
Solution Found: Node 0, Level 0
Solution Cost: -95.0000000000

When called from within MibS, the results are even different yet. If I build SHA 4377871 with debugging and just run

./mibs -instance ~/DataSets/MIBLPLib/iblpZhang/T1-1-3.mps -MibS_turnOffDefaultCuts 1 -MibS_useImprovingDirectionIC 1 -MibS_useFractionalCuts 0 -MibS_branchStrategy 0

the following assert trips:

mibs: /home/ted/Projects/MibS/src/MibSBilevel.cpp:520: MibSSolType MibSBilevel::checkBilevelFeasibility(bool): Assertion `(objVal - lowerObj) <= etol' failed.

This is because that same instance gets a solution value of

Solution Found: Node 0, Level 0
Solution Cost: -66.0000000000

and I can't replicate this on the command line.