Initializing help system before first use

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.
Topic areas
Callback, Limits
Synopsis
int XPRS_CC XPRSaddcbgapnotify(XPRSprob prob, void (XPRS_CC *gapnotify)(XPRSprob cbprob, void* cbdata, double* p_relgapnotifytarget, double* p_absgapnotifytarget, double* p_absgapnotifyobjtarget, double* p_absgapnotifyboundtarget), void* data, int priority);
Arguments
prob 
The current problem.
gapnotify 
The callback function.
cbprob 
The current problem.
cbdata 
The user-defined data passed as data when setting up the callback with XPRSaddcbgapnotify.
p_relgapnotifytarget 
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.
p_absgapnotifytarget 
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.
p_absgapnotifyobjtarget 
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.
p_absgapnotifyboundtarget 
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.
data 
A user-defined data to be passed to the callback function, 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* data,
  double* p_relgapnotifytarget, double* p_absgapnotifytarget,
  double* p_absgapnotifyobjtarget, double* p_absgapnotifyboundtarget)
{
  double obj, bound, relgap;
  XPRSgetdblattrib(prob, XPRS_MIPOBJVAL, &obj);
  XPRSgetdblattrib(prob, XPRS_BESTBOUND, &bound);
  if (obj != 0.0 || bound != 0.0)
    relgap = fabs((obj - bound)/ max(fabs(obj), fabs(bound)));
  else
    relgap = 0.0;
  if (relgap<=0.10) {
    printf("Gap reached 10%");
    *p_relgapnotifytarget = 0.1;
  }
  if (relgap<=0.01) {
    printf("Gap reached 1%");
    *p_relgapnotifytarget = -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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