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problem.setcbprenode

Purpose
Set a user callback to be called during MISLP after the set-up of the SLP problem to be solved at a node, but before SLP optimization
Synopsis

problem.setcbprenode(callback, data)

feas = callback(my_prob, my_object)
Arguments
callback 
The function to be called after the set-up of the SLP problem to be solved at a node. callback returns an integer value. If the return value is nonzero, then further processing of the node will be terminated (it is declared infeasible).
my_prob 
The problem passed to the callback function.
my_object 
The user-defined object passed as data to setcbprenode.
feas 
feasibility flag. If callback return a nonzero, the node is declared infeasible.
Example
The following example sets up a callback function to be executed at each node before the SLP optimization starts. The array IntList contains a list of integer variables, and the function prints the bounds on these variables. 
IntList = [...]
prob.setcbprenode(CBPreNode, IntList)
A suitable callback function might resemble the following: 
def CBPreNode(myProb, intlist):
  for i in intlist:
    LO,UP = [],[]
    myProb.getlb(LO,i,i)
    myProb.getub(UP,i,i)
    lb,ub = LO[0], UP[0]
    if lb > 0 or ub < xp.infinity:
      print("Col {0}: {1} <= {2}".format(i,lb,ub)
  return 0
Further information

If a node can be identified as infeasible by the callback function, then the initial optimization at the current node is avoided, as well as further exploration of the node.


Related topics
problem.setcboptnode, problem.setcbslpnode

Parent Topic Xpress problem methods

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