XPRSaddcbgapnotify
XPRSaddcbgapnotify |
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
int XPRS_CC XPRSaddcbgapnotify(XPRSprob prob, void (XPRS_CC *f_gapnotify)(XPRSprob my_prob, void* my_object, double* newRelGapNotifyTarget, double* newAbsGapNotifyTarget, double* newAbsGapNotifyObjTarget, double* newAbsGapNotifyBoundTarget), void* object, int priority);
Arguments
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prob
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The current problem.
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f_gapnotify
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The callback function.
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my_prob
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The current problem.
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my_object
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The user-defined object passed as
object when setting up the callback with
XPRSaddcbgapnotify.
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newRelGapNotifyTarget
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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.
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newAbsGapNotifyTarget
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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.
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newAbsGapNotifyObjTarget
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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.
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newAbsGapNotifyBoundTarget
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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.
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object
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A user-defined object to be passed to the callback function,
f_gapnotify.
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priority
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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.
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Example
The following example prints a message when the gap reaches 10% and 1%
void XPRS_CC gapnotify(XPRSprob prob, void* object,
double* newRelGapNotifyTarget, double* newAbsGapNotifyTarget,
double* newAbsGapNotifyObjTarget, double* newAbsGapNotifyBoundTarget)
{
double obj, bound, relgap;
XPRSgetdblattrib(prob, XPRS_MIPOBJVAL, &obj);
XPRSgetdblattrib(prob, XPRS_BESTBOUND, &bound);
relgap = fabs( (obj-bound)/obj );
if (relgap<=0.10) {
printf("Gap reached 10%");
*newRelGapNotifyTarget = 0.1;
}
if (relgap<=0.01) {
printf("Gap reached 1%");
*newRelGapNotifyTarget = -1; /* Don't call gapnotify again */
}
}
XPRSsetdblcontrol( prob, XPRS_MIPRELGAPNOTIFY, 0.10 );
XPRSaddcbgapnotify( prob, gapnotify, NULL, 0 );
XPRSmipoptimize(prob, "");
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.
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