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# XPRSaddcblplog

Purpose
Declares a simplex log callback function which is called after every LPLOG iterations of the simplex algorithm. This callback function will be called in addition to any callbacks already added by XPRSaddcblplog.
Topic areas
Callback, LP
Synopsis
`int XPRS_CC XPRSaddcblplog(XPRSprob prob, int (XPRS_CC *lplog)(XPRSprob cbprob, void* cbdata), void* data, int priority);`
Arguments

prob | The current problem.
lplog | The callback function, which takes arguments cbprob and cbdata, and has an integer return value. This function is called every LPLOG simplex iterations including iteration 0 and the final iteration.
cbprob | The problem passed to the callback function, lplog.
cbdata | The user-defined data passed as data when setting up the callback.
data | A user-defined data to be passed to the callback function, lplog.
priority | An integer that determines the order in which multiple lplog 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.

Related controls
Integer

LPLOG | Frequency and type of simplex algorithm log.

Example
The following code sets a callback function, lpLog, to be called every 10 iterations of the optimization:

    XPRSsetintcontrol(prob,XPRS_LPLOG,10);
    XPRSsetintcontrol(prob,XPRS_LPLOGSTYLE,0);
    XPRSaddcblplog(prob,lpLog,NULL,0);
    XPRSreadprob(prob,"problem","");
    XPRSmipoptimize(prob,"");

The callback function may resemble:

    int XPRS_CC lpLog(XPRSprob cbprob, void *data)
    {
      int iter; double obj;

      XPRSgetintattrib(cbprob, XPRS_SIMPLEXITER, &iter);
      XPRSgetdblattrib(cbprob, XPRS_LPOBJVAL, &obj);
      printf("At iteration %d objval is %g\n", iter, obj);
      return 0;
    }

Further information
If the callback function returns a nonzero value the solution process will be interrupted.
Related topics
XPRSremovecblplog, XPRSaddcbbarlog, XPRSaddcbmiplog, XPRSaddcbmessage.
Parent Topic Console and Library Functions

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