[Coin-discuss] integer column bounds fixed by CBC/CLP?

[John J Forrest]

a) Yes the MIP can add more rows during Branch and Cut - these will be at
end.
b) If you use CglPreProcess it has methods originalRows and originalColumns
which point back while the problem is preprocessed - after postprocessing
these will just be 0,1,2.

John Forrest


                                                                           
             Kish Shen                                                     
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                                       Re: [Coin-discuss] integer column   
                                       bounds fixed by CBC/CLP?            
             06/27/06 11:12 PM                                             
                                                                           
                                                                           
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On Sunday 25 June 2006 11:36, John J Forrest wrote:
> This was deliberate so that further processing could be done.  Even if
you
> reset bounds then some information has been modified e.g. best solution.
> Suggested way of doing repeated runs is as in Cbc/examples/repeat.cpp and
> also see references to referenceSolver in CbcModel.hpp
>
> John Forrest
>
>
John, thanks for your quick reply!

I have updated my code so that it saves a reference solver just before
doing
the MIP, and then after the solve, extract the required solution
information
(variable solution values, reduced costs, etc.), and then reset to the
reference solver.

Am I correct in that the MIP can add extra rows to the problem by posting
more
cuts to the problem? Also, can the presolve remove columns/rows from the
problem? Are these changes visible in the model after the solving? CPLEX
and
XPRESS allows the user to extra information from the probelm using the
original rows/column numbers, and this is important for our usage, as they
map to the user's variables and constraints.

Cheers,

Kish Shen

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