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XPRSaddcbpreintsol

XPRSaddcbpreintsol

Purpose
Declares a user integer solution callback function, called when an integer solution is found by heuristics or during the branch and bound search, but before it is accepted by the Optimizer. This callback function will be called in addition to any integer solution callbacks already added by XPRSaddcbpreintsol.
Synopsis
int XPRS_CC XPRSaddcbpreintsol(XPRSprob prob, void (XPRS_CC *f_preintsol)(XPRSprob my_prob, void *my_object, int soltype, int *ifreject, double *cutoff), void *object, int priority);
Arguments
prob 
The current problem.
f_preintsol 
The callback function which takes five arguments, my_prob, my_object, soltype, ifreject and cutoff, and has no return value. This function is called when an integer solution is found, but before the solution is accepted by the Optimizer, allowing the user to reject the solution.
my_prob 
The problem passed to the callback function, f_preintsol.
my_object 
The user-defined object passed as object when setting up the callback with XPRSaddcbpreintsol.
soltype 
The type of MIP solution that has been found: Set to 1 if the solution was found using a heuristic. Otherwise, it will be the global feasible solution to the current node of the global search.
0 
The continuous relaxation solution to the current node of the global search, which has been found to be global feasible.
1 
A MIP solution found by a heuristic.
2 
A MIP solution provided by the user.
3 
A solution resulting from refinement of primal or dual violations of a previous MIP solution.
ifreject 
Set this to 1 if the solution should be rejected.
cutoff 
The new cutoff value that the Optimizer will use if the solution is accepted. If the user changes cutoff, the new value will be used instead. The cutoff value will not be updated if the solution is rejected.
object 
A user-defined object to be passed to the callback function, f_preintsol.
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.
Related controls
Integer
MIPABSCUTOFF 
Branch and Bound: If the user knows that they are interested only in values of the objective function which are better than some value, this can be assigned to MIPABSCUTOFF. This allows the Optimizer to ignore solving any nodes which may yield worse objective values, saving solution time. When a MIP solution is found a new cut off value is calculated and the value can be obtained from the CURRMIPCUTOFF attribute. The value of CURRMIPCUTOFF is calculated using the MIPRELCUTOFF and MIPADDCUTOFF controls.

Further information
1. If a solution is rejected, the Optimizer will drop the found solution without updating any attributes, including the cutoff value. To change the cutoff value when rejecting a solution, the control MIPABSCUTOFF should be set instead.
2. When a node solution ( soltype = 0) is rejected, the node itself will be dropped without further branching.
3. To retrieve the integer solution, use either XPRSgetlpsol or XPRSgetpresolvesol. XPRSgetmipsol will not return the newly found solution because it has not been saved at this point.
Related topics
XPRSremovecbpreintsol, XPRSaddcbintsol.

Parent Topic Console and Library Functions

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