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# ColgenInstance:get(++What, -Value)

Obtain global problem information.

What
  Specification for information wanted (atom)
Value
  Returned value of What

## Description

Retrieve information about solver constraints and results, for the colgen instance ColgenInstance. What can take one of the following values:

`dual(+Id)`
  Returns the floating-point value of the current dual value for the constraint having identifier Id. See also `sp_obj` below.

`sp_obj(+Id)`
  Returns the sub problem objective terms currently associated associated with the constraint having identifier Id. This will be a term `Val*Var` where Val is the current dual value for the constraint as also returned by `ColgenInstance:get(dual(Id), Val)` and Var is the subproblem variable in the implicit sum term of the constraint. It is the users responsibility to get all relevant terms of the current cost function and ensure that subproblem solutions posted to the colgen instance have a non-negative cost.

`vars`
  Returns a list of all variables currently associated with the colgen instance `ColgenInstance`.

`non_zero_vars`
  Returns a list of all variables currently associated with the colgen instance `ColgenInstance` that have a non-zero optimal solution. This may be more efficient than retrieving all problem variables after solution, since very many variables can be generated and most will have a zero value in the optimal solution.

`frac_vars`
  Returns a list of all variables currently associated with the colgen instance `ColgenInstance` that have a fractional optimal solution. This is intended for use primarily in user-defined problem branching predicates.