[Cbc] Fixing variables

[Haroldo Gambini Santos]

LP reoptimization is efficient, but MIP reoptimization is not.

Gurobi/CPLEX try at least to reuse (and repair if necessary) a feasible 
solution that was found before. If you could repair manually a solution 
found previously and inform it to CBC with MIPstart before reoptimizing 
maybe you could get some speedup.

Em 3/7/20 2:51 PM, Ted Ralphs escreveu:
> The preprocessor tries to figure out if variables can be fixed, even 
> for variables whose upper and lower bounds are not explicitly equal. I 
> don't imagine there would be much gain from re-modeling.
>
> Ted
>
> On Fri, Mar 6, 2020 at 12:08 PM Daniel Grace <danwgrace at gmail.com 
> <mailto:danwgrace at gmail.com>> wrote:
>
>     Hi,
>
>     Say I have a problem (model) MIP or ILP and I want to fix some
>     variables, rather than remodel the problem with such variables
>     replaced by their respective values i.e. by setting each
>     corresponding column upper value and column lower value to
>     matching values. Does CBC deal with such variables efficiently, or
>     is it better to remodel the problem?
>
>     Thanks
>
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>
> -- 
> Dr. Ted Ralphs
> Professor, Industrial and Systems Engineering
> Lehigh University
> (610) 628-1280
> ted 'at' lehigh 'dot' edu
> coral.ie.lehigh.edu/~ted <http://coral.ie.lehigh.edu/~ted>
>
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-- 
=============================================================
Haroldo Gambini Santos
Computing Department
Universidade Federal de Ouro Preto - UFOP
email: haroldo at ufop.edu.br
home/research page: www.decom.ufop.br/haroldo


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the most important.
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