Initializing help system before first use

problem.addcbpreintsol

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 addcbpreintsol.
Synopsis

problem.addcbpreintsol(callback, data, priority)

(ifreject, newcutoff) = callback(my_prob, my_object, soltype, cutoff)
Arguments
callback 
The callback function which takes four arguments, my_prob, my_object, soltype and cutoff, returns a tuple of two elements. 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, callback.
my_object 
The user-defined object passed as object when setting up the callback with addcbpreintsol.
soltype 
The type of MIP solution that has been found.
0 
The continuous relaxation solution to the current node of the tree search, which has been found to be integer 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.
cutoff 
The current cutoff value.
ifreject 
If a nonzero value is returned in the first position of the tuple, the solution will be rejected.
newcutoff 
A new cutoff value can be returned in the second position of the tuple, to be used by the Optimizer if the solution is accepted. The returned newcutoff value will not be updated if the solution is rejected.
data 
A user-defined object to be passed to the callback function, callback.
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.
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 is rejected ( isheuristic = 0), the node itself will be dropped without further branching.
3. To retrieve the integer solution, use either problem.getCallbackSolution or problem.getCallbackPresolveSolution. problem.getSolution will not return the newly found solution because it has not been saved at this point.
Related topics
problem.removecbpreintsol, problem.addcbintsol.

Parent Topic Xpress problem methods

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