HxSolution Class¶

class hexaly.optimizer.HxSolution¶: Solution to the optimization model. A solution carries the values of all expressions in the model. It is used to retrieve the values of all expressions (getting the solution), or to set the values of some decisions (setting the solution).

Summary¶

Attributes¶
`status`	Status of the solution.

Methods¶
`set_value`	Sets the value of the given expression in this solution.
`get_value`	Returns the value of the given expression in this solution.
`is_violated`	Returns true if the given expression is violated in this solution.
`is_undefined`	Returns true if the given expression has an undefined value in this solution.
`get_status`	Returns the status of the solution.
`get_objective_bound`	Returns the bound computed by the solver for the given objective.
`get_objective_gap`	Returns the gap computed by the solver for the given objective.
`clear`	Clear the solution and set all decisions to zero.

Instance methods¶

HxSolution.set_value(expr, value)¶

Sets the value of the given expression in this solution. Only decisions can be set. Only allowed in state HxState.STOPPED. The value must be a double, integer, boolean or HxInterval. If the solver was not launched, this value will be used as an initial value for the decision.

Parameters:

expr (HxExpression) – Decision
value – Value assigned to the decision in this solution.

HxSolution.get_value(expr)¶

Returns the value of the given expression in this solution. Only allowed in states HxState.PAUSED or HxState.STOPPED. The type of the returned value depends on the type of the HxExpression. It can be a boolean, an integer, a double, a HxInterval, a HxCollection or a HxArray.

Parameters:: expr (HxExpression) – Expression
Returns:: Value of the expression in this solution.
Return type:: bool, int, double, HxInterval, HxCollection or HxArray

HxSolution.is_violated(expr)¶

Returns true if the given expression is violated in this solution.

An expression can be violated in 2 cases:

it is a constraint and its value is 0
it is a double and its value is NaN (Not a Number)
it is an integer or boolean with no valid value (arithmetic or out of bounds exception).

Only allowed in states HxState.PAUSED or HxState.STOPPED.

Returns:: True if this expression is violated in this solution.
Return type:: bool

HxSolution.is_undefined(expr)¶

Returns true if the given expression has an undefined value in this solution.

An expression can be undefined in 4 cases:

It is a double and its value is NaN (Not a Number).
It is an integer or boolean with no valid value (arithmetic or out of bounds exception).
It is an interval with at least one undefined bound.
It is the result of any ill-defined operation (at with out of bounds index or operations on undefined values for instance).

Only allowed in states HxState.PAUSED or HxState.STOPPED.

Returns:: True if this expression has an undefined value in this solution.
Return type:: bool
Since:: 7.0

HxSolution.get_status()¶

Returns the status of the solution. Only allowed in states HxState.PAUSED or HxState.STOPPED.

You can also use the shortcut member status

Returns:: Status of the solution.
Return type:: HxSolutionStatus

HxSolution.get_objective_bound(obj_index)¶

Returns the bound computed by the solver for the given objective. If the solver has never been launched, this method returns a large integer number or math.inf. Only allowed in states HxState.PAUSED or HxState.STOPPED.

Parameters:: obj_index (int) – Index of the objective
Returns:: The bound of the objective
Return type:: int or double

HxSolution.get_objective_gap(obj_index)¶

Returns the gap computed by the solver for the given objective. The gap for feasible solutions is defined as:

\[|obj - bound| / \max(1, |obj|, |bound|)\]

Infeasible solutions have an infinite gap.

Only allowed in states HxState.PAUSED or HxState.STOPPED.

Parameters:: obj_index (int) – Index of the objective
Returns:: The gap of the objective
Return type:: double

HxSolution.clear()¶: Clear the solution and set all decisions to zero. Only allowed in state HxState.STOPPED.

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.

HxSolution.status¶: Status of the solution. This attribute is read-only. It is a shortcut for get_status().