appsi.solvers.gurobi.rst

Gurobi

Handling Gurobi licenses through the APPSI interface

In order to obtain performance benefits when re-solving a Pyomo model with Gurobi repeatedly, Pyomo has to keep a reference to a gurobipy model between calls to :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.solve()`. Depending on the Gurobi license type, this may "consume" a license as long as any APPSI-Gurobi interface exists (i.e., has not been garbage collected). To release a Gurobi license for other processes, use the :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.release_license()` method as shown below. Note that :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.release_license()` must be called on every instance for this to actually release the license. However, releasing the license will delete the gurobipy model which will have to be reconstructed from scratch the next time :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.solve()` is called, negating any performance benefit of the persistent solver interface.

>>> opt = appsi.solvers.Gurobi()  # doctest: +SKIP
>>> results = opt.solve(model)  # doctest: +SKIP
>>> opt.release_license()  # doctest: +SKIP

Also note that both the :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.available()` and :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.solve()` methods will construct a gurobipy model, thereby (depending on the type of license) "consuming" a license. The :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.available()` method has to do this so that the availability does not change between calls to :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.available()` and :py:meth:`~pyomo.contrib.appsi.solvers.gurobi.Gurobi.solve()`, leading to unexpected errors.

.. autoclass:: pyomo.contrib.appsi.solvers.gurobi.GurobiResults
  :members:
  :inherited-members:
  :undoc-members:
  :show-inheritance:

.. autoclass:: pyomo.contrib.appsi.solvers.gurobi.Gurobi
  :members:
  :inherited-members:
  :undoc-members:
  :show-inheritance: