[Coin-discuss] Basis status query

[John J Forrest]

Stefan Vigerske pointed out to me that OsiClp was returning an incorrect
CoinWarmStartBasis status for an L row.  I realized that Clp has the
correct status but that for several years I have been carefully swapping
atLowerBound and atUpperBound on artificials when using
OsiClpSolverInterface.  I thought that the Osi convention was to use the
status of the slack which would be at lower bound if at 0 i.e. tight on
upper bound on constraint.

Testing with DyLP, Glpk and Osl they all gave atUpperBound for an L row so
I intend to fix my error.  I also intend to add a simple test in the Osi
unit test to make sure that all solvers that can return a basis will give
the same result.

Can anyone see any problems with this.  I don't want to break anyone's
code.  I also hope that other solvers which give a basis will return
correct status.

John Forrest