problem.addcbgapnotify

Purpose

Declares a gap notification callback, to be called when a MIP solve reaches a predefined target, set using the miprelgapnotify, mipabsgapnotify, mipabsgapnotifyobj, and/or mipabsgapnotifybound controls.

Synopsis

 problem.addcbgapnotify(callback, data, priority)
 (RelGapNotify, AbsGapNotify, AbsGapNotifyObj, AbsGapNotifyBound) = callback(my_prob, my_object)

Arguments

callback	The callback function.
object	A user-defined object that wil be passed into the callback callback.
priority	An integer that determines the order in which multiple gap notification callbacks will be invoked. The callback added with the higher priority will be called before a callback with a lower priority. Set to 0 if not required.
my_prob	The current problem.
my_object	The user-defined object passed as object when setting up the callback with addcbgapnotify.
RelGapNotify	The value the miprelgapnotify control will be set to after this callback. May be modified within the callback in order to set a new notification target. Can be None.
AbsGapNotify	The value the mipabsgapnotify control will be set to after this callback. May be modified within the callback in order to set a new notification target. Can be None.
AbsGapNotifyObj	The value the mipabsgapnotifyobj control will be set to after this callback. May be modified within the callback in order to set a new notification target. Can be None.
AbsGapNotifyBound	The value the mipabsgapnotifybound control will be set to after this callback. May be modified within the callback in order to set a new notification target. Can be None.
data	A user-defined object to be passed to the callback function, callback.
priority	An integer that determines the order in which multiple estimate callbacks will be invoked. The callback added with a higher priority will be called before a callback with a lower priority. Set to 0 if not required.

Example

The following example prints a message when the gap reaches 10% and 1%

def gapnotify(prob, object):

    obj = prob.attributes.mipobjval
    bound = prob.attributes.bestbound

    # If no solutions were found, just return a tuple of None's
    if prob.attributes.mipsols == 0:
        return None, None, None, None

    if obj != 0 and bound != 0:
        relgap = abs((obj - bound) / max(abs(obj), abs(bound)))
    else:
        relgap = 0

    newRelGapNotifyTarget = -1

    if relgap <= 0.1:
        print('Gap reached 10%')
        newRelGapNotifyTarget = 0.1

    if relgap <= 0.01:
        print('Gap reached 1%')
        newRelGapNotifyTarget = -1 # Don't call gapnotify again

    # return a quadruple with new values, or
    # None for those that should not be set
    return (newRelGapNotifyTarget, None, None, None)

prob.controls.miprelgapnotify = 0.1
prob.addcbgapnotify(gapnotify, None, 0)
prob.mipoptimize('')

Further information

The target values that caused the callback to be triggered will automatically be reset to prevent the same callback from being fired again.

Contents

Index

Glossary

Search Results

problem.addcbgapnotify

problem.addcbgapnotify