Presolve Dual Reductions

Type

Selection

Range

The settings listed below

Default

On

This option controls whether the AIMMS Presolver should apply dual reductions. Possible values are:

  • Off

  • On

Dual reduction techniques remove feasible or even optimal solutions while guaranteeing that at least one optimal solution remains, as long as the original problem was feasible.

For example, assume that the binary variable \(y\) does not appear in the objective. Furthermore, we assume that \(y\) only appears in one constraint in the math program, namely in:

\[x + y + z <= 1\]

In any feasible solution in which \(y\) equals 1 we can change its solution value to 0 while the solution remains feasible without changing the objective value. Therefore we can fix \(y\) to 0.

Note

  • Dual reductions are automatically switched off if the model uses lazy constraints (either through a callback or a pool).

  • This option has only an effect when solving a nonlinear model and the option Nonlinear Presolve is switched on, or when solving a linear, quadratic or quadratically-constrained model and the option Linear Presolve is switched on, or if the function GMP::Instance::CreatePresolved is used.

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