AppInterface.update

Purpose

Sends a progress update notification for a single metric from the model to the Xpress Insight system.

Synopsis

update(self, metric: xpressinsight.Metric, value: Union[float, int, xpressinsight.ObjSense]) -> None

Arguments

metric	The type of metric to update.
value	The value of the metric to update.

Example

Notify Insight that the current best solution value is 51.9.

>>> insight.update(Metric.OBJVAL, 51.9)

Automatic updating of metrics during optimization can be achieved by calling the update function from within a suitable solver callback:

>>> def on_gap_notify(prob, app):
...
...     num_sol = prob.attributes.mipsols
...     app.insight.update(xi.Metric.NUMSOLS, num_sol)
...
...     if num_sol == 0:
...         # Can only occur when mipabsgapnotifybound is used.
...         # Don't call gapnotify again.
...         return None, None, None, None
...
...     objective = prob.attributes.mipobjval
...     best_bound = prob.attributes.bestbound
...
...     if best_bound != 0 or objective != 0:
...         gap = abs(objective - best_bound) / \
...               max(abs(best_bound), abs(objective))
...     else:
...         gap = 0
...
...     app.insight.update(xi.Metric.OBJVAL, objective)
...     app.insight.update(xi.Metric.GAP, gap)
...
...     if gap > 1e-6:
...         new_rel_gap_notify_target = gap - 1e-6
...     else:
...         # Don't call gapnotify again.
...         new_rel_gap_notify_target = -1
...
...     return new_rel_gap_notify_target, None, None, None

The above callback can then be attached via the Xpress Python API:

>>> prob = xp.problem()
...
... # TODO: Define the optimization problem
...
... # Optionally reset progress and set the objective sense
... self.insight.reset_progress()
... self.insight.update(xi.Metric.OBJSENSE, prob.attributes.objsense)
...
... prob.controls.miprelgapnotify = 1e20
... prob.addcbgapnotify(on_gap_notify, self, 0)
...
... prob.solve()

Further information

This function allows the model to report back progress to the system where it is accessible by a client for display.

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AppInterface.update

AppInterface.update