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XPRSsetcbsepnode

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Purpose

Declares a separate callback function to specify how to separate a node in the Branch and Bound tree using a global object. A node can be separated by applying either cuts or bounds to each node. These are stored in the cut pool.

Synopsis

int XPRS_CC XPRSsetcbsepnode(XPRSprob prob, int (XPRS_CC *fse)(XPRSprob my_prob, void *my_object, int ibr, int iglsel, int ifup, double curval), void *object);

Arguments

prob	The current problem.
fse	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, fse.
my_object	The user-defined object passed as object when setting up the callback with XPRSsetcbsepnode.
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, fse .

Example

This example minimizes a problem, before defining a user separate callback function for the global search:

XPRSminim(prob,"");
XPRSsetcbsepnode(prob,nodeSep,NULL);
XPRSglobal(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);
  }
  XPRSsetbranchcuts(my_prob, 1, &index);
  return 0;
}

Further information

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

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

Related topics

XPRSsetbranchcuts, XPRSsetcbestimate, XPRSstorecuts.

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