[SCIP] MIP Pre-solver

[Benjamin Müller]

Dear Serge,

sorry for the late reply, your mail slipped through my attention.

1. Alternatively, you could extend the linear constraint handler and 
implement another presolving technique that tightens/changes some 
coefficients.

2. Do you want to link both variables via a linear equality constraint, 
e.g., x_j = a z_j + b? If that is the case, then you want to aggregate 
variables. For this you can use SCIPaggregateVars() or 
SCIPmultiaggregateVar() for multi-aggregations. If this is not what you 
want to do, then please provide more information on what you want to 
achieve. Thanks!

Best,
Benjamin

On 12/11/19 1:50 PM, Serge Kruk wrote:
> Hello all,
> 
> I am trying to write a pre-solver for MIP. I want to confirm the 
> following (or fix my misunderstanding):
> Consider a set simple linear constraints $\sum_i a_{ij} x_j \le b_i$
> 
> 1. Say that I want to change the coefficients $a_ij$ of a row (to scale, 
> for example).
> 
> I have not seen a simple way to just change the coefficient. Must I 
> delete the constraint and create a scaled constraint?
> 
> 2. Say I want to change the variable of a column.  Replacing $x_j$ by 
> $z_j$ and creating another constraint relating the two.
> 
> Again, I have not seen a simple way to do this except deleting all 
> constraints and re-creating all of them.
> 
> I trust that I am wrong and someone can enlighten me.
> 
> Cheers
> Serge
> 
> 
> 
> 
> 
>        Serge G. Kruk Ph.D.
>        Associate Professor kruk at oakland.edu <mailto:kruk at oakland.edu>
> Department of Mathematics and Statistics <http://www.oakland.edu/math>
> Oakland University <http://www.oakland.edu>,
>        Rochester, MI.  48309
> 
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-- 
______________________________
Benjamin Müller
Zuse Institute Berlin
Takustr. 7, 14195 Berlin
benjamin.mueller at zib.de
+49 30 841 85-195