[Coin-lpsolver] basisIsAvailable()

[John J Forrest]

Francois,

The description of basisIsAvailable does not say anything about an optimal 
basis.  I thought it was more so you can distinguish Volume algorithm.

I can add optimalBasisIsAvailable if you want but can the OsiCpx 
maintainer tell me what they think basisIsAvailable means?

John



Francois Margot <fmargot at andrew.cmu.edu> 
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11/08/2005 03:25 PM

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Subject
[Coin-lpsolver] basisIsAvailable()







The function OsiClpSolverInterface::basisIsAvailable() always returns
true. This is a little bit dangerous. If modifications are made to the
solver after the last optimization (change of bound on variables, in
particular), the available basis might be (primal or dual, or both) 
infeasible.

Then, calling cut generators such as Gomory and Reduce-and-Split might
result in invalid cuts. The only way (as far as I can tell) to prevent 
this
is to rely on basisIsAvailable() to stop the cut generator if the current
basis is not optimal anymore.

Cplex is tracking the status of the basis accurately, but Clp does not.
Is it possible to fix that?

Thanks

Francois
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