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# 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.
Synopsis
`addcbpreintsol(prob, cb, prio = 0)`
Arguments

prob | The problem pointer to which the callback is added.
cb | The callback function to add.
prio | The priority of the callback. If multiple callbacks are registered for the same event then they are invoked according to their priority ordering.

Return value
Always returns 0 (zero).
Further information
Note the general callback conventions:

- a callback function may return either an integer or a list.
- if the C callback function has an integer return type then the value returned to the optimizer is the integer value returned or the list's "ret" element (if it exists).
- if the C callback function has output arguments then these arguments are taken from the list that is returned by the callback function.
- the R callback function will only receive the input arguments of the C callback

The preintsol callback supports the following input arguments (in this order):

cbprob
  The problem passed to the callback function, preintsol.
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.
cutoff
  The new cutoff value that the Optimizer will use if the solution is accepted. If cutoff is assigned a value, the new value will be used instead. The cutoff value will not be updated if the solution is rejected.

The preintsol callback supports the following output arguments:

ret
  An integer that will interrupt the search if non-zero.
reject
  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.

Parent Topic R interface reference manual

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