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XSLPsetcboptnode

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Purpose

Set a user callback to be called during MISLP when an optimal SLP solution is obtained at a node

Synopsis

int XPRS_CC XSLPsetcboptnode(XSLPprob Prob, int (XPRS_CC *UserFunc) (XSLPprob myProb, void *myObject, int *feas), void *Object);

Arguments

Prob	The current SLP problem.
UserFunc	The function to be called when an optimal SLP solution is obtained at a node. UserFunc returns an integer value. If the return value is nonzero, or if the feasibility flag is set nonzero, then further processing of the node will be terminated (it is declared infeasible).
myProb	The problem passed to the callback function.
myObject	The user-defined object passed as Object to XSLPsetcboptnode.
feas	Address of an integer containing the feasibility flag. If UserFunc sets the flag nonzero, the node is declared infeasible.
Object	Address of a user-defined object, which can be used for any purpose by the function. Object is passed to UserFunc as myObject.

Example

The following example defines a callback function to be executed at each node when an SLP optimal solution is found. If there are significant penalty errors in the solution, the node is declared infeasible.

XSLPsetcboptnode(Prob, CBOptNode, NULL);

A suitable callback function might resemble the following:

int XPRS_CC CBOptNode(XSLPprob myProb, void *Obj, int *feas) {
  double Total, ObjVal;
  XSLPgetdblattrib(myProb, XSLP_ERRORCOSTS, &Total);
  XSLPgetdblattrib(myProb, XSLP_OBJVAL, &ObjVal);
  if (fabs(Total) > fabs(ObjVal) * 0.001 &&  
    fabs(Total) > 1) *feas = 1;
  return 0;

Further information

If a node is declared infeasible from the callback function, the cost of exploring the node further will be avoided.

This callback must be used in place of XPRSsetcboptnode when optimizing with MISLP.

When used with VB, the callback function has the prototype:

Public Function mycbfunc (ByVal prob As Long, ByVal object As Long) As Long

Related topics

XSLPsetcbprenode, XSLPsetcbslpnode

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