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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
prob 
The current problem.
f_gapnotify 
The callback function.
my_prob 
The current problem.
my_object 
The user-defined object passed as object when setting up the callback with XPRSaddcbgapnotify.
newRelGapNotifyTarget 
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.
newAbsGapNotifyTarget 
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.
newAbsGapNotifyObjTarget 
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.
newAbsGapNotifyBoundTarget 
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.
object 
A user-defined object to be passed to the callback function, f_gapnotify.
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% 
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.
Related topics
MIPRELGAPNOTIFY, MIPABSGAPNOTIFY, MIPABSGAPNOTIFYOBJ, MIPABSGAPNOTIFYBOUND, XPRSremovecbgapnotify.

Parent Topic Console and Library Functions

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