GurobiPersistent

(class from pyomo.contrib.solver.solvers.gurobi.gurobi_persistent)

class pyomo.contrib.solver.solvers.gurobi.gurobi_persistent.GurobiPersistent(**kwds)

Bases: GurobiDirectBase, PersistentSolverBase, Observer

__init__(**kwds)

Methods

__init__(**kwds)
add_block(block)	Add a block to the model.
add_constraints(cons)	Add constraints to the model.
add_sos_constraints(cons)
api_version()	Return the public API supported by this interface.
available()	Test if the solver is available on this system.
cbCut(con)	Add a cut within a callback.
cbGet(what)
cbGetNodeRel(variables)
cbGetSolution(variables)
cbLazy(con)
cbSetSolution(variables, solution)
cbUseSolution()
env()
get_gurobi_param_info(param)	Get information about a gurobi parameter.
get_linear_constraint_attr(con, attr)	Get the value of an attribute on a gurobi linear constraint.
get_model_attr(attr)	Get the value of an attribute on the Gurobi model.
get_quadratic_constraint_attr(con, attr)	Get the value of an attribute on a gurobi quadratic constraint.
get_sos_attr(con, attr)	Get the value of an attribute on a gurobi sos constraint.
get_var_attr(var, attr)	Get the value of an attribute on a gurobi var.
is_persistent()
release_license()
remove_block(block)	Remove a block from the model.
remove_constraints(cons)	Remove constraints from the model.
remove_sos_constraints(cons)
reset()
set_callback([func])	Specify a callback for gurobi to use.
set_gurobi_param(param, val)	Set a gurobi parameter.
set_instance(pyomo_model, **kwds)	Set an instance of the model.
set_linear_constraint_attr(con, attr, val)	Set the value of an attribute on a gurobi linear constraint.
set_objective(obj)	Set current objective for the model.
set_var_attr(var, attr, val)	Set the value of an attribute on a gurobi variable.
solve(model, **kwds)	Solve a Pyomo model.
update(**kwds)
update_parameters(params)	Update parameters on the model.
update_variables(variables)	Update variables on the model.
version()	Return the solver version found on the system.
write(filename)	Write the model to a file (e.g., and lp file).

Attributes

CONFIG
name
config	Instance configuration; see CONFIG documentation on derived class

Member Documentation

classmethod api_version()

Return the public API supported by this interface.

Returns:

A solver API enum object

Return type:

SolverAPIVersion

add_block(block: BlockData)

Add a block to the model.

add_constraints(cons)

Add constraints to the model.

available()

Test if the solver is available on this system.

Nominally, this will return True if the solver interface is valid and can be used to solve problems and False if it cannot. Note that for licensed solvers there are a number of “levels” of available: depending on the license, the solver may be available with limitations on problem size or runtime (e.g., ‘demo’ vs. ‘community’ vs. ‘full’). In these cases, the solver may return a subclass of enum.IntEnum, with members that resolve to True if the solver is available (possibly with limitations). The Enum may also have multiple members that all resolve to False indicating the reason why the interface is not available (not found, bad license, unsupported version, etc).

Returns:

available – An enum that indicates “how available” the solver is. Note that the enum can be cast to bool, which will be True if the solver is runnable at all and False otherwise.

Return type:

Availability

cbCut(con)

Add a cut within a callback.

Parameters:

con (pyomo.core.base.constraint.ConstraintData) – The cut to add

cbGetNodeRel(variables)

Parameters:

variables (Var or iterable of Var)

cbGetSolution(variables)

Parameters:

variables (iterable of vars)

cbLazy(con)

Parameters:

con (pyomo.core.base.constraint.ConstraintData) – The lazy constraint to add

get_gurobi_param_info(param)

Get information about a gurobi parameter.

Parameters:

param (str) – The gurobi parameter to get info for. See Gurobi documentation for possible options.

Return type:

six-tuple containing the parameter name, type, value, minimum value, maximum value, and default value.

get_linear_constraint_attr(con, attr)

Get the value of an attribute on a gurobi linear constraint.

Parameters:

• con (pyomo.core.base.constraint.ConstraintData) – The pyomo constraint for which the corresponding gurobi constraint attribute should be retrieved.

• attr (str) – The attribute to get. See the Gurobi documentation

get_model_attr(attr)

Get the value of an attribute on the Gurobi model.

Parameters:

attr (str) – The attribute to get. See Gurobi documentation for descriptions of the attributes.

get_quadratic_constraint_attr(con, attr)

Get the value of an attribute on a gurobi quadratic constraint.

Parameters:

• con (pyomo.core.base.constraint.ConstraintData) – The pyomo constraint for which the corresponding gurobi constraint attribute should be retrieved.

• attr (str) – The attribute to get. See the Gurobi documentation

get_sos_attr(con, attr)

Get the value of an attribute on a gurobi sos constraint.

Parameters:

• con (pyomo.core.base.sos.SOSConstraintData) – The pyomo SOS constraint for which the corresponding gurobi SOS constraint attribute should be retrieved.

• attr (str) – The attribute to get. See the Gurobi documentation

get_var_attr(var, attr)

Get the value of an attribute on a gurobi var.

Parameters:

• var (pyomo.core.base.var.VarData) – The pyomo var for which the corresponding gurobi var attribute should be retrieved.

• attr (str) – The attribute to get. See gurobi documentation

is_persistent() → bool

Returns:

is_persistent – True if the solver is a persistent solver.

Return type:

bool

remove_block(block: BlockData)

Remove a block from the model.

remove_constraints(cons)

Remove constraints from the model.

set_callback(func=None)

Specify a callback for gurobi to use.

Parameters:

func (function) –

The function to call. The function should have three arguments. The first will be the pyomo model being solved. The second will be the GurobiPersistent instance. The third will be an enum member of gurobipy.GRB.Callback. This will indicate where in the branch and bound algorithm gurobi is at. For example, suppose we want to solve

\[ \begin{align}\begin{aligned}min 2*x + y\\s.t.\\ y >= (x-2)**2\\ 0 <= x <= 4\\ y >= 0\\ y integer\end{aligned}\end{align} \]

as an MILP using extended cutting planes in callbacks.

>>> from gurobipy import GRB
>>> import pyomo.environ as pyo
>>> from pyomo.core.expr.taylor_series import taylor_series_expansion
>>> from pyomo.contrib import appsi
>>>
>>> m = pyo.ConcreteModel()
>>> m.x = pyo.Var(bounds=(0, 4))
>>> m.y = pyo.Var(within=pyo.Integers, bounds=(0, None))
>>> m.obj = pyo.Objective(expr=2*m.x + m.y)
>>> m.cons = pyo.ConstraintList()  # for the cutting planes
>>>
>>> def _add_cut(xval):
...     # a function to generate the cut
...     m.x.value = xval
...     return m.cons.add(m.y >= taylor_series_expansion((m.x - 2)**2))
...
>>> _c = _add_cut(0)  # start with 2 cuts at the bounds of x
>>> _c = _add_cut(4)  # this is an arbitrary choice
>>>
>>> opt = appsi.solvers.Gurobi()
>>> opt.config.stream_solver = True
>>> opt.set_instance(m)
>>> opt.gurobi_options['PreCrush'] = 1
>>> opt.gurobi_options['LazyConstraints'] = 1
>>>
>>> def my_callback(cb_m, cb_opt, cb_where):
...     if cb_where == GRB.Callback.MIPSOL:
...         cb_opt.cbGetSolution(variables=[m.x, m.y])
...         if m.y.value < (m.x.value - 2)**2 - 1e-6:
...             cb_opt.cbLazy(_add_cut(m.x.value))
...
>>> opt.set_callback(my_callback)
>>> res = opt.solve(m)

set_gurobi_param(param, val)

Set a gurobi parameter.

Parameters:

• param (str) – The gurobi parameter to set. Options include any gurobi parameter. Please see the Gurobi documentation for options.

• val (any) – The value to set the parameter to. See Gurobi documentation for possible values.

set_instance(pyomo_model, **kwds)

Set an instance of the model.

set_linear_constraint_attr(con, attr, val)

Set the value of an attribute on a gurobi linear constraint.

Parameters:

• con (pyomo.core.base.constraint.ConstraintData) – The pyomo constraint for which the corresponding gurobi constraint attribute should be modified.

• attr (str) –

  The attribute to be modified. Options are:

  CBasis DStart Lazy

• val (any) – See gurobi documentation for acceptable values.

set_objective(obj: ObjectiveData)

Set current objective for the model.

set_var_attr(var, attr, val)

Set the value of an attribute on a gurobi variable.

Parameters:

• var (pyomo.core.base.var.VarData) – The pyomo var for which the corresponding gurobi var attribute should be modified.

• attr (str) –

  The attribute to be modified. Options are:

  Start VarHintVal VarHintPri BranchPriority VBasis PStart

• val (any) – See gurobi documentation for acceptable values.

solve(model, **kwds) → Results

Solve a Pyomo model.

Parameters:

• model (BlockData) – The Pyomo model to be solved

• **kwargs – Additional keyword arguments (including solver_options - passthrough options; delivered directly to the solver (with no validation))

Returns:

results – A results object

Return type:

Results

update_parameters(params)

Update parameters on the model.

update_variables(variables)

Update variables on the model.

version()

Return the solver version found on the system.

Returns:

version – A tuple representing the version

Return type:

tuple

write(filename)

Write the model to a file (e.g., and lp file).

Parameters:

filename (str) – Name of the file to which the model should be written.

CONFIG = <pyomo.contrib.solver.solvers.gurobi.gurobi_persistent.GurobiPersistentConfig object>

config

Instance configuration; see CONFIG documentation on derived class