[SCIP] Handling Inactive multiaggregated/fixed variables

[Hulst, Rolf van der (UT-EEMCS)]

Dear SCIP-community,


I'd like to read the constraint matrix from SCIP after presolving into a sparse matrix format (e.g. Ax <= b) after running SCIP to presolve the instance.

I get the variables of the transformed problem using "SCIPgetVars(scip)" and "SCIPgetNVars(scip)".
However, when I read the constraints, some inactive variables which were fixed or aggregated during presolving are still present in some of the constraints.

After fixing/aggregating these variables, are the lhs/rhs and/or variable coefficients updated correspondingly, and can I ignore this variable entry in the constraint when determining the corresponding sparse matrix row? (e.g. I would simply call  "SCIPconsGetRhs()" to determine b_i and skip any inactive variables when determining coefficients for a_i). Or should I call SCIPgetMultiAggrVars() and SCIPgetMultiAggrConstant() in order to update the coefficient of the aggregated variables and rhs in that constraint? And are these aggregated variables pointing to the original or the transformed variables? How should I handle these in order to correctly read the problem into matrix format Ax<=b?

Best,

Rolf

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