Inheritance diagram for operations_research::SCIPInterface:

Public Member Functions
	SCIPInterface (MPSolver *solver)

	~SCIPInterface () override

void	SetOptimizationDirection (bool maximize) override
	Not cached.

MPSolver::ResultStatus	Solve (const MPSolverParameters &param) override

bool	SupportsDirectlySolveProto (std::atomic< bool > *interrupt) const override

MPSolutionResponse	DirectlySolveProto (LazyMutableCopy< MPModelRequest > request, std::atomic< bool > *interrupt) override

void	Reset () override

double	infinity () override

void	SetVariableBounds (int var_index, double lb, double ub) override
	Modifies bounds of an extracted variable.

void	SetVariableInteger (int var_index, bool integer) override
	Modifies integrality of an extracted variable.

void	SetConstraintBounds (int row_index, double lb, double ub) override
	Modify bounds of an extracted variable.

void	AddRowConstraint (MPConstraint *ct) override
	Adds a linear constraint.

bool	AddIndicatorConstraint (MPConstraint *ct) override

void	AddVariable (MPVariable *var) override
	Add a variable.

void	SetCoefficient (MPConstraint constraint, const MPVariable variable, double new_value, double old_value) override
	Changes a coefficient in a constraint.

void	ClearConstraint (MPConstraint *constraint) override
	Not cached.

void	SetObjectiveCoefficient (const MPVariable *variable, double coefficient) override
	Cached.

void	SetObjectiveOffset (double value) override
	Cached.

void	ClearObjective () override
	Clear objective of all its terms.

void	BranchingPriorityChangedForVariable (int var_index) override

int64_t	iterations () const override

int64_t	nodes () const override

MPSolver::BasisStatus	row_status (int constraint_index) const override
	Returns the basis status of a row.

MPSolver::BasisStatus	column_status (int variable_index) const override
	Returns the basis status of a constraint.

bool	IsContinuous () const override

bool	IsLP () const override
	Returns true if the problem is continuous and linear.

bool	IsMIP () const override
	Returns true if the problem is discrete and linear.

void	ExtractNewVariables () override
	Extracts the variables that have not been extracted yet.

void	ExtractNewConstraints () override
	Extracts the constraints that have not been extracted yet.

void	ExtractObjective () override
	Extracts the objective.

std::string	SolverVersion () const override
	Returns a string describing the underlying solver and its version.

bool	InterruptSolve () override

void *	underlying_solver () override
	Returns the underlying solver.

bool	NextSolution () override

void	SetCallback (MPCallback *mp_callback) override
	MPCallback API.

bool	SupportsCallbacks () const override

Public Member Functions inherited from operations_research::MPSolverInterface
	MPSolverInterface (MPSolver *solver)

virtual	~MPSolverInterface ()

virtual void	Write (const std::string &filename)

double	best_objective_bound () const

double	objective_value () const
	Returns the objective value of the best solution found so far.

bool	CheckSolutionIsSynchronized () const

virtual bool	CheckSolutionExists () const

bool	CheckSolutionIsSynchronizedAndExists () const
	Handy shortcut to do both checks above (it is often used).

int	last_variable_index () const
	Returns the index of the last variable extracted.

bool	variable_is_extracted (int var_index) const

void	set_variable_as_extracted (int var_index, bool extracted)

bool	constraint_is_extracted (int ct_index) const

void	set_constraint_as_extracted (int ct_index, bool extracted)

bool	quiet () const
	Returns the boolean indicating the verbosity of the solver output.

void	set_quiet (bool quiet_value)
	Sets the boolean indicating the verbosity of the solver output.

MPSolver::ResultStatus	result_status () const
	Returns the result status of the last solve.

virtual double	ComputeExactConditionNumber () const

virtual void	SetStartingLpBasis (const std::vector< MPSolver::BasisStatus > &, const std::vector< MPSolver::BasisStatus > &)
	See MPSolver::SetStartingLpBasis().

Additional Inherited Members
Public Types inherited from operations_research::MPSolverInterface
enum	SynchronizationStatus { MUST_RELOAD , MODEL_SYNCHRONIZED , SOLUTION_SYNCHRONIZED }

Static Public Attributes inherited from operations_research::MPSolverInterface
static constexpr int64_t	kUnknownNumberOfIterations = -1

static constexpr int64_t	kUnknownNumberOfNodes = -1

Protected Member Functions inherited from operations_research::MPSolverInterface
void	ExtractModel ()
	Extracts model stored in MPSolver.

void	ResetExtractionInformation ()
	Resets the extraction information.

void	InvalidateSolutionSynchronization ()

void	SetCommonParameters (const MPSolverParameters &param)
	Sets parameters common to LP and MIP in the underlying solver.

void	SetMIPParameters (const MPSolverParameters &param)
	Sets MIP specific parameters in the underlying solver.

void	SetUnsupportedDoubleParam (MPSolverParameters::DoubleParam param)
	Sets an unsupported double parameter.

void	SetDoubleParamToUnsupportedValue (MPSolverParameters::DoubleParam param, double value)
	Sets a supported double parameter to an unsupported value.

Protected Attributes inherited from operations_research::MPSolverInterface
MPSolver *const	solver_

SynchronizationStatus	sync_status_
	Indicates whether the model and the solution are synchronized.

MPSolver::ResultStatus	result_status_

bool	maximize_
	Optimization direction.

int	last_constraint_index_
	Index in MPSolver::variables_ of last constraint extracted.

int	last_variable_index_
	Index in MPSolver::constraints_ of last variable extracted.

double	objective_value_
	The value of the objective function.

double	best_objective_bound_
	The value of the best objective bound. Used only for MIP solvers.

bool	quiet_
	Boolean indicator for the verbosity of the solver output.

Static Protected Attributes inherited from operations_research::MPSolverInterface
static const int	kDummyVariableIndex = 0
	-------— MPSolverInterface -------—

Detailed Description

Definition at line 67 of file scip_interface.cc.

Constructor & Destructor Documentation

◆ SCIPInterface()

operations_research::SCIPInterface::SCIPInterface ( MPSolver * solver )

explicit

Definition at line 258 of file scip_interface.cc.

◆ ~SCIPInterface()

operations_research::SCIPInterface::~SCIPInterface ( )

override

Definition at line 263 of file scip_interface.cc.

Member Function Documentation

◆ AddIndicatorConstraint()

bool operations_research::SCIPInterface::AddIndicatorConstraint ( MPConstraint * )

overridevirtual

Adds an indicator constraint. Returns true if the feature is supported by the underlying solver.

Reimplemented from operations_research::MPSolverInterface.

Definition at line 499 of file scip_interface.cc.

◆ AddRowConstraint()

void operations_research::SCIPInterface::AddRowConstraint ( MPConstraint * ct )

overridevirtual

Adds a linear constraint.

Implements operations_research::MPSolverInterface.

Definition at line 495 of file scip_interface.cc.

◆ AddVariable()

void operations_research::SCIPInterface::AddVariable ( MPVariable * var )

overridevirtual

Add a variable.

Implements operations_research::MPSolverInterface.

Definition at line 504 of file scip_interface.cc.

◆ BranchingPriorityChangedForVariable()

void operations_research::SCIPInterface::BranchingPriorityChangedForVariable ( int var_index )

overridevirtual

As of 2019-05, SCIP does not support setting branching priority for variables in models that have already been solved. Therefore, we force reset the model when setting the priority on an already extracted variable.

Note: this is a more drastic step than merely changing the sync_status. This may be slightly conservative, as it is technically possible that the extraction has occurred without a call to Solve().

Reimplemented from operations_research::MPSolverInterface.

Definition at line 483 of file scip_interface.cc.

◆ ClearConstraint()

void operations_research::SCIPInterface::ClearConstraint ( MPConstraint * constraint )

overridevirtual

Not cached.

Constraint may not have been extracted yet.

Set coefficient to zero by subtracting the old coefficient value.

Implements operations_research::MPSolverInterface.

Definition at line 429 of file scip_interface.cc.

◆ ClearObjective()

void operations_research::SCIPInterface::ClearObjective ( )

overridevirtual

Clear objective of all its terms.

Clear linear terms

Variable may have not been extracted yet.

Note: we don't clear the objective offset here because it's not necessary (it's always reset anyway in ExtractObjective) and we sometimes run into crashes when clearing the whole model (see http://test/OCL:253365573:BASE:253566457:1560777456754:e181f4ab). It's not worth to spend time investigating this issue.

Implements operations_research::MPSolverInterface.

Definition at line 459 of file scip_interface.cc.

◆ column_status()

MPSolver::BasisStatus operations_research::SCIPInterface::column_status ( int variable_index ) const

inlineoverridevirtual

Returns the basis status of a constraint.

Implements operations_research::MPSolverInterface.

Definition at line 105 of file scip_interface.cc.

◆ DirectlySolveProto()

MPSolutionResponse operations_research::SCIPInterface::DirectlySolveProto	(	LazyMutableCopy< MPModelRequest >	request,
		std::atomic< bool > *	interrupt )

overridevirtual

Reimplemented from operations_research::MPSolverInterface.

Definition at line 884 of file scip_interface.cc.

◆ ExtractNewConstraints()

void operations_research::SCIPInterface::ExtractNewConstraints ( )

overridevirtual

Extracts the constraints that have not been extracted yet.

Find the length of the longest row.

Add each new constraint.

See http://scip.zib.de/doc/html/cons__linear_8h.php#aa7aed137a4130b35b168812414413481 for an explanation of the parameters.

Implements operations_research::MPSolverInterface.

Definition at line 551 of file scip_interface.cc.

◆ ExtractNewVariables()

void operations_research::SCIPInterface::ExtractNewVariables ( )

overridevirtual

Extracts the variables that have not been extracted yet.

Define new variables

The true objective coefficient will be set later in ExtractObjective.

Add new variables to existing constraints.

The variable is new, so we know the previous coefficient value was 0 and we can directly add the coefficient.

Implements operations_research::MPSolverInterface.

Definition at line 506 of file scip_interface.cc.

◆ ExtractObjective()

void operations_research::SCIPInterface::ExtractObjective ( )

overridevirtual

Extracts the objective.

Linear objective: set objective coefficients for all variables (some might have been modified).

Constant term: change objective offset.

Implements operations_research::MPSolverInterface.

Definition at line 651 of file scip_interface.cc.

◆ infinity()

double operations_research::SCIPInterface::infinity ( )

overridevirtual

Reimplemented from operations_research::MPSolverInterface.

Definition at line 317 of file scip_interface.cc.

◆ InterruptSolve()

bool operations_research::SCIPInterface::InterruptSolve ( )

inlineoverridevirtual

Reimplemented from operations_research::MPSolverInterface.

Definition at line 124 of file scip_interface.cc.

◆ IsContinuous()

bool operations_research::SCIPInterface::IsContinuous ( ) const

inlineoverridevirtual

--— Misc --— Queries problem type. For simplicity, the distinction between continuous and discrete is based on the declaration of the user when the solver is created (example: GLPK_LINEAR_PROGRAMMING vs. GLPK_MIXED_INTEGER_PROGRAMMING), not on the actual content of the model. Returns true if the problem is continuous.

Implements operations_research::MPSolverInterface.

Definition at line 110 of file scip_interface.cc.

◆ IsLP()

bool operations_research::SCIPInterface::IsLP ( ) const

inlineoverridevirtual

Returns true if the problem is continuous and linear.

Implements operations_research::MPSolverInterface.

Definition at line 111 of file scip_interface.cc.

◆ IsMIP()

bool operations_research::SCIPInterface::IsMIP ( ) const

inlineoverridevirtual

Returns true if the problem is discrete and linear.

Implements operations_research::MPSolverInterface.

Definition at line 112 of file scip_interface.cc.

◆ iterations()

int64_t operations_research::SCIPInterface::iterations ( ) const

overridevirtual

---— Query statistics on the solution and the solve ---— Returns the number of simplex iterations. The problem must be discrete, otherwise it crashes, or returns kUnknownNumberOfIterations in NDEBUG mode.

NOTE(user): As of 2018-12 it doesn't run in the stubby server, and is a specialized call, so it's ok to crash if the status is broken.

Implements operations_research::MPSolverInterface.

Definition at line 907 of file scip_interface.cc.

◆ NextSolution()

bool operations_research::SCIPInterface::NextSolution ( )

overridevirtual

MULTIPLE SOLUTIONS SUPPORT The default behavior of scip is to store the top incidentally generated integer solutions in the solution pool. The default maximum size is 100. This can be adjusted by setting the param limits/maxsol. There is no way to ensure that the pool will actually be full.

You can also ask SCIP to enumerate all feasible solutions. Combined with an equality or inequality constraint on the objective (after solving once to find the optimal solution), you can use this to find all high quality solutions. See https://scip.zib.de/doc/html/COUNTER.php. This behavior is not supported directly through MPSolver, but in theory can be controlled entirely through scip parameters.

Make sure we have successfully solved the problem and not modified it.

Reimplemented from operations_research::MPSolverInterface.

Definition at line 893 of file scip_interface.cc.

◆ nodes()

int64_t operations_research::SCIPInterface::nodes ( ) const

overridevirtual

Returns the number of branch-and-bound nodes. The problem must be discrete, otherwise it crashes, or returns kUnknownNumberOfNodes in NDEBUG mode.

NOTE(user): Same story as iterations(): it's OK to crash here.

This is the total number of nodes used in the solve, potentially across multiple branch-and-bound trees. Use limits/totalnodes (rather than limits/nodes) to control this value.

Implements operations_research::MPSolverInterface.

Definition at line 914 of file scip_interface.cc.

◆ Reset()

void operations_research::SCIPInterface::Reset ( )

overridevirtual

--— Model modifications and extraction --— Resets extracted model.

We hold calls to SCIPinterruptSolve() until the new scip_ is fully built.

Remove existing one but keep it alive to copy parameters from it.

Install the new one.

Copy all existing parameters from the previous SCIP to the new one. This ensures that if a user calls multiple times SetSolverSpecificParametersAsString() and then Reset() is called, we still take into account all parameters. Note though that at the end of Solve(), parameters are reset so after Solve() has been called, only the last set parameters are kept.

Implements operations_research::MPSolverInterface.

Definition at line 265 of file scip_interface.cc.

◆ row_status()

MPSolver::BasisStatus operations_research::SCIPInterface::row_status ( int constraint_index ) const

inlineoverridevirtual

Returns the basis status of a row.

Implements operations_research::MPSolverInterface.

Definition at line 101 of file scip_interface.cc.

◆ SetCallback()

void operations_research::SCIPInterface::SetCallback ( MPCallback * mp_callback )

overridevirtual

MPCallback API.

CALLBACK SUPPORT:

We support MPSolver's callback API via MPCallback. See ./linear_solver_callback.h.
We also support SCIP's more general callback interface, built on 'constraint handlers'. See ./scip_callback.h and test, these are added directly to the underlying SCIP object, bypassing SCIPInterface. The former works by calling the latter.

Reimplemented from operations_research::MPSolverInterface.

Definition at line 1148 of file scip_interface.cc.

◆ SetCoefficient()

void operations_research::SCIPInterface::SetCoefficient	(	MPConstraint *	constraint,
		const MPVariable *	variable,
		double	new_value,
		double	old_value )

overridevirtual

Changes a coefficient in a constraint.

The modification of the coefficient for an extracted row and variable is not cached.

SCIP does not allow to set a coefficient directly, so we add the difference between the new and the old value instead.

The modification of an unextracted row or variable is cached and handled in ExtractModel.

Implements operations_research::MPSolverInterface.

Definition at line 404 of file scip_interface.cc.

◆ SetConstraintBounds()

void operations_research::SCIPInterface::SetConstraintBounds	(	int	index,
		double	lb,
		double	ub )

overridevirtual

Modify bounds of an extracted variable.

Not cached if the row has been extracted.

Implements operations_research::MPSolverInterface.

Definition at line 388 of file scip_interface.cc.

◆ SetObjectiveCoefficient()

void operations_research::SCIPInterface::SetObjectiveCoefficient	(	const MPVariable *	variable,
		double	coefficient )

overridevirtual

Cached.

Implements operations_research::MPSolverInterface.

Definition at line 448 of file scip_interface.cc.

◆ SetObjectiveOffset()

void operations_research::SCIPInterface::SetObjectiveOffset ( double value )

overridevirtual

Cached.

Implements operations_research::MPSolverInterface.

Definition at line 454 of file scip_interface.cc.

◆ SetOptimizationDirection()

void operations_research::SCIPInterface::SetOptimizationDirection ( bool maximize )

overridevirtual

Not cached.

Implements operations_research::MPSolverInterface.

Definition at line 343 of file scip_interface.cc.

◆ SetVariableBounds()

void operations_research::SCIPInterface::SetVariableBounds	(	int	index,
		double	lb,
		double	ub )

overridevirtual

Modifies bounds of an extracted variable.

Not cached if the variable has been extracted.

Implements operations_research::MPSolverInterface.

Definition at line 351 of file scip_interface.cc.

◆ SetVariableInteger()

void operations_research::SCIPInterface::SetVariableInteger	(	int	index,
		bool	integer )

overridevirtual

Modifies integrality of an extracted variable.

Not cached if the variable has been extracted.

Implements operations_research::MPSolverInterface.

Definition at line 367 of file scip_interface.cc.

◆ Solve()

MPSolver::ResultStatus operations_research::SCIPInterface::Solve ( const MPSolverParameters & param )

overridevirtual

--— Solve --— Solves problem with specified parameter values. Returns true if the solution is optimal.

"status_" may encode a variety of failure scenarios, many of which would correspond to another MPResultStatus than ABNORMAL, but since SCIP is a moving target, we use the most likely error code here (abnormalities, often numeric), and rely on the user enabling output to see more details.

Note: SCIP does not provide any incrementality.

Todo: (user): Is that still true now (2018) ?

Set log level.

Special case if the model is empty since SCIP expects a non-empty model.

When the value of callback_ is changed, callback_reset_ is set and code above you call Reset() that should have cleared scip_constraint_handler_. Here we assert that if this has not happened then callback_ value has not changed.

Time limit.

We first set our internal MPSolverParameters from param and then set any user specified internal solver, ie. SCIP, parameters via solver_specific_parameter_string_. Default MPSolverParameters can override custom parameters (for example for presolving) and therefore we apply MPSolverParameters first.

Use the solution hint if any.

We start by creating an empty partial solution.

We start by creating the all-zero solution.

Fill the other variables from the given solution hint.

Todo: (user): I more or less copied this from the SCIPreadSol() code that reads a solution from a file. I am not sure what SCIPisTransformed() is or what is the difference between the try and add version. In any case this seems to always call SCIPaddSolFree() for now and it works.

Solve.

Get the results.

If optimal or feasible solution is found.

Check the status: optimal, infeasible, etc.

To be consistent with the other solvers.

Todo: (user): We could introduce our own "infeasible or unbounded" status.

Implements operations_research::MPSolverInterface.

Definition at line 684 of file scip_interface.cc.

◆ SolverVersion()

std::string operations_research::SCIPInterface::SolverVersion ( ) const

inlineoverridevirtual

Returns a string describing the underlying solver and its version.

Implements operations_research::MPSolverInterface.

Definition at line 118 of file scip_interface.cc.

◆ SupportsCallbacks()

bool operations_research::SCIPInterface::SupportsCallbacks ( ) const

inlineoverridevirtual

Reimplemented from operations_research::MPSolverInterface.

Definition at line 160 of file scip_interface.cc.

◆ SupportsDirectlySolveProto()

bool operations_research::SCIPInterface::SupportsDirectlySolveProto ( std::atomic< bool > * ) const

overridevirtual

DirectlySolveProto() shall only be used if SupportsDirectlySolveProto() is true.

DirectlySolveProto() solves a MPModelRequest, bypassing the MPSolver data structures entirely. Like MPSolver::SolveWithProto(), optionally takes in an 'interrupt' boolean.

ScipSolveProto doesn't solve concurrently.

Interruption via atomic<bool> is not directly supported by SCIP.

Reimplemented from operations_research::MPSolverInterface.

Definition at line 873 of file scip_interface.cc.

◆ underlying_solver()

void * operations_research::SCIPInterface::underlying_solver ( )

inlineoverridevirtual

Returns the underlying solver.

Implements operations_research::MPSolverInterface.

Definition at line 134 of file scip_interface.cc.

The documentation for this class was generated from the following file:

ortools/linear_solver/scip_interface.cc

Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ SCIPInterface()

◆ ~SCIPInterface()

Member Function Documentation

◆ AddIndicatorConstraint()

◆ AddRowConstraint()

◆ AddVariable()

◆ BranchingPriorityChangedForVariable()

◆ ClearConstraint()

◆ ClearObjective()

◆ column_status()

◆ DirectlySolveProto()

◆ ExtractNewConstraints()

◆ ExtractNewVariables()

◆ ExtractObjective()

◆ infinity()

◆ InterruptSolve()

◆ IsContinuous()

◆ IsLP()

◆ IsMIP()

◆ iterations()

◆ NextSolution()

◆ nodes()

◆ Reset()

◆ row_status()

◆ SetCallback()

◆ SetCoefficient()

◆ SetConstraintBounds()

◆ SetObjectiveCoefficient()

◆ SetObjectiveOffset()

◆ SetOptimizationDirection()

◆ SetVariableBounds()

◆ SetVariableInteger()

◆ Solve()

◆ SolverVersion()

◆ SupportsCallbacks()

◆ SupportsDirectlySolveProto()

◆ underlying_solver()