XPRSaddcbsepnode

Purpose

This function is deprecated and may be removed in future releases. Please use branching objects instead. Declares a separate callback function to specify how to branch on a node in the branch and bound tree using a global object. A node can be branched by applying either cuts or bounds to each node. These are stored in the cut pool. This callback function will be called in addition to any callbacks already added by XPRSaddcbsepnode.

Synopsis

 int XPRS_CC XPRSaddcbsepnode(XPRSprob prob, int (XPRS_CC *f_sepnode)(XPRSprob my_prob, void *my_object, int ibr, int iglsel, int ifup, double curval), void *object, int priority);

Arguments

prob	The current problem.
f_sepnode	The callback function, which takes six arguments, my_prob, my_object, ibr, iglsel, ifup and curval, and has an integer return value.
my_prob	The problem passed to the callback function, f_sepnode.
my_object	The user-defined object passed as object when setting up the callback with XPRSaddcbsepnode.
ibr	The branch number.
iglsel	The global entity number.
ifup	The direction of branch on the global entity (same as ibr).
curval	Current value of the global entity.
object	A user-defined object to be passed to the callback function, f_sepnode .
priority	An integer that determines the order in which callbacks of this type 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

This example solves a MIP, using a separation callback function to branch on fractional integer variables. It assumes the presence of an estimation callback function (not shown), defined by XPRSaddcbestimate, to identify a fractional integer variable.

 XPRSaddcbsepnode(prob,nodeSep,NULL,0);
 XPRSmipoptimize(prob,"");

where the function nodeSep may be defined as follows:

int nodeSep(XPRSprob my_prob, void *my_object, int ibr,
             int iglsel, int ifup, double curval)
 {
   XPRScut index;
   double dbd;

   if( ifup )
   {
     dbd = floor(xval);
     XPRSstorebounds(my_prob, 1, &iglsel, "U", &dbd, &index);
   }
   else
   {
     dbd = ceil(xval);
     XPRSstorebounds(my_prob, 1, &iglsel, "L", &dbd, &index);
   }
   XPRSsetbranchbounds(prob, index);
   return 0;
 }

Further information

1. The return value of the f_sepnode callback function is currently ignored.

2. Consider using the more flexible branching objects, as described for the XPRS_bo_create function.

3. The user separate routine is called nbr times where nbr is returned by the estimate callback function, XPRSaddcbestimate. This allows multi-way branching to be performed.

4. The bounds and/or cuts to be applied at a node must be specified in the user separate routine by calling XPRSsetbranchbounds and/or XPRSsetbranchcuts.

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XPRSaddcbsepnode

XPRSaddcbsepnode