LocalSolver Class¶

Summary¶

Instance methods¶

LocalSolver.solve()¶

Solves the model. This method returns only when the time limit, the iteration limit, the objective bounds are reached or when the method stop() is called. The model must be closed to launch the resolution.

LocalSolver.stop()¶

Aborts the resolution previously launched using solve(). If no resolution was launched, this method does nothing. Called from another thread or callback, this method enables users to stop the resolution properly. Solution and statistics remain valid. This method can be called in any state, notably in state LSState.RUNNING. Note that the effect of this method is not immediate. In particular when called within a callback, the resolution will not be stopped before the end of the callback.

See:

solve()

See:

add_callback()

LocalSolver.get_state()¶

Gets the state of this LocalSolver environment. This method can be called in any state. In particular, this method can be called in state LSState.RUNNING.

You can also use the shortcut member state

Returns:

State of LocalSolver.

Return type:

.LSState

LocalSolver.get_model()¶

Gets the model associated to this LocalSolver environment. Once the model is created and closed, the solver can be launched with solve().

You can also use the shortcut member model

Returns:

Model

Return type:

LSModel

LocalSolver.get_param()¶

Gets the parameters of this LocalSolver environment.

You can also use the shortcut member param

Returns:

Parameters

Return type:

LSParam

LocalSolver.create_phase()¶

Adds a new phase to this LocalSolver environment. Only allowed in states LSState.MODELING or LSState.STOPPED.

Returns:

Created phase.

Return type:

LSPhase

LocalSolver.get_phase(phase_id)¶

Gets the phase with the given index.

You can also use the shortcut collection phases.

Parameters:

phase_id (int) – Index of the phase

Returns:

Phase

Return type:

LSPhase

LocalSolver.get_nb_phases()¶

Gets the number of phases.

You can also use the shortcut collection phases.

Returns:

Number of phases.

Return type:

int

LocalSolver.get_solution()¶

Gets the best solution found by the solver. If the solver has not been started at least once, all the decision variables of the solution are set to 0, or to their closest bound if 0 is not part of their domain (such a solution may be infeasible). Only allowed in states LSState.PAUSED or LSState.STOPPED.

You can also use the shortcut member solution

Returns:

The best solution.

Return type:

LSSolution

LocalSolver.get_statistics()¶

Gets the statistics of this LocalSolver environment. Statistics are reset to zero before each resolution. Only allowed in states LSState.PAUSED or LSState.STOPPED. Note that for performance reasons, this function always returns the same object.

You can also use the shortcut member statistics

Returns:

Statistics.

Return type:

LSStatistics

LocalSolver.save_environment(filename)¶

Export a complete environment or a model to a file.

Currently, this function supports 2 file formats:

• LSB: with this format, the complete environment (model, parameters, solution, etc.) is exported. This format is useful to debug or replay a model in the same conditions. Since the produced file is binary, it offers good performance and space efficiency.

• LSP: with this format, only the model is exported in the LSP language. This format is useful to have a quick view of the optimization model or to perform some modifications. However, the file may be heavy for big models and the exact reproductibility is not guaranteed since the parameters from one execution to another may differ.

The chosen file format is determined by the file suffix. An exception is thrown if the provided file suffix is not supported. The suffix may optionally be followed by .gz. In that case, this function produces a compressed result (using deflate algorithm).

Parameters:

filename (str) – Name of the file.

Since:

3.0

LocalSolver.load_environment(filename)¶

Import a complete environment from a file. Only allowed in state LSState.MODELING. The current model must be empty.

The only format supported is LSB. You can obtain a such file thanks to save_environment().

The chosen file format is determined by the file suffix. An exception is thrown if the provided file suffix is not supported. The suffix may optionally be followed by .gz. In that case, this function uncompress the stream before reading.

Parameters:

filename (str) – Name of the file.

Since:

3.0

LocalSolver.compute_inconsistency()¶

Computes an inconsistency core for this model. Only allowed in state LSState.STOPPED.

Returns:

Inconsistency core

Return type:

LSInconsistency

Since:

6.0

LocalSolver.add_callback(type, callback)¶

Add a new callback for a specific event type. The callback will be called each time the given event occurs. When a callback is called, the solver is paused. You can stop the resolution from a callback, retrieve the current solution, retrieve the statistics of the solver and, in general, call all the methods marked as “allowed in state LSState.PAUSED”.

The same callback can be used for different events. Only allowed in states LSState.STOPPED or LSState.MODELING.

The callback function must accept 2 parameters that are respectively the LocalSolver environment and the type of the event.

Parameters:

• type (LSCallbackType) – Event to watch.

• callback (function) – User callback. Cannot be null.

Since:

4.0

LocalSolver.remove_callback(type, callback)¶

Remove the callback for the given event type.

Parameters:

• type (LSCallbackType) – Event

• callback (function) – User callback to delete

Returns:

False if the callback was not added for the given event, True otherwise.

Return type:

bool

Since:

4.0

LocalSolver.delete()¶

Deletes the LocalSolver objects and releases the licence token. It deletes the native memory used by LocalSolver and makes the LocalSolver licence available for another LocalSolver model. This method is automatically called by the garbage collector of Python when it detects that this LocalSolver object is no longer needed or reachable. This method is also automatically called when you use LocalSolver in a with statement.

Instance attributes¶

All get/set methods have their attribute counterpart. You can use them as shortcuts to improve the readability or your models and codes.

LocalSolver.state¶

State of the solver. This attribute is read-only. It is a shortcut for get_state().

LocalSolver.model¶

Model associated to this environment. This attribute is read-only. It is a shortcut for get_model().

LocalSolver.param¶

Parameters of the model. This attribute is read-only. It is a shortcut for get_param().

LocalSolver.phases¶

List of the phases of the model. This attribute is read-only. The returned object is iterable, supports the len function and can be indexed with integers. It is a shortcut for get_phase() and get_nb_phases() methods. Please note, that you still have to use create_phase() to add phases.

LocalSolver.solution¶

Best solution found. This attribute is read-only. It is a shortcut for get_solution().

LocalSolver.statistics¶

Statistics. This attribute is read-only. It is a shortcut for get_statistics().

Special operators and methods¶

LocalSolver.__str__()¶

Returns a string representation of this LocalSolver environment. This representation provides useful info related to the model, the parameters, and the phases (if any). Useful for debugging or logging purposes.

Returns:

String representation of this LocalSolver.

Return type:

str