8.4.5. Callback

Functions

MDOsetcallbackfunc()	Set up a user defined callback function
MDOgetcallbackfunc()	Retrieve the current user defined callback function
MDOcbget()	Retrieve additional data about the optimization progress
MDOcbcut()	Add a new cutting plane to the MIP model
MDOcbbranch()	Indicate a new branching by specifying a variable and a split point between the lower and upper bounds of this variable
MDOcbsolution()	Provide a new feasible solution for a MIP model

int MDOsetcallbackfunc(MDOmodel *model, callbackfn cb, void *usrdata)

Set up a user defined callback function.

Parameters

• model (MDOmodel*) – [in] The model object.

• cb (callbackfn) –

  [in] The callback function. Type callbackfn is defined as:

  typedef int (*callbackfn)(const MDOmodel* model, void* cbdata, int where, const void* usrdata);
  

• usrdata (void*) – [in] The user defined callback context.

Returns

A response code that specifies the status of the function.

int MDOgetcallbackfunc(MDOmodel *model, callbackfn *cb)

Retrieve the current user defined callback function.

Parameters

• model (MDOmodel*) – [in] The model object.

• cb (callbackfn*) –

  [out] The place to hold current callback function. Type callbackfn defined as:

  typedef int (*callbackfn)(const MDOmodel* model, void* cbdata, int where, const void* usrdata);
  

Returns

A response code that specifies the status of the function.

int MDOcbget(void *cbdata, int where, int what, void *resultP)

Retrieve additional data about the optimization progress.

Parameters

• cbdata (void*) – [in] The cbdata argument passed into user callback function.

• where (int) – [in] The where argument passed into user callback function.

• what (int) – [in] The data ID requested by the user callback.

• resultP (void*) – [out] The place to hold requested data, its type depends on the data requested.

Returns

A response code that specifies the status of the function.

int MDOcbcut(void *cbdata, int cutlen, const int *cutind, const double *cutval, char cutsense, double cutrhs)

Add a new cutting plane to the MIP model.

Parameters

• cbdata (void*) – [in] The cbdata argument passed into user callback function.

• cutlen (int) – [in] The number of variables associated with new cutting plane.

• cutind (const int*) – [in] The list of variable indices associated with new cutting plane.

• cutval (const double*) – [in] The list of variable coefficients associated with new cutting plane.

• cutsense (char) – [in] The sense of new cutting plane.

• cutrhs (double) – [in] The right-hand-side value of new cutting plane.

Returns

A zero or negative response code that specifies the status of the function, otherwise a positive number to indicate the submission status:

• 1: Submission is valid but incorrect (infeasible, etc)

• 2: Submission is correct but not being accepted.

int MDOcbbranch(void *cbdata, int index, double value, int way)

Indicate a new branching by specifying a variable and a split point between the lower and upper bounds of this variable.

Parameters

• cbdata (void*) – [in] The cbdata argument passed into user callback function.

• index (int) – [in] The variable index.

• value (double) – [in] The split point. It should be between the lower and upper bounds of variable.

• way (int) –

  [in] The branch to consider first. Valid options are:

  • <0: the down-way branch is considered first.

  • >0: the up-way branch is considered first.

Returns

A zero or negative response code that specifies the status of the function, otherwise a positive number to indicate the submission status:

• 1: Submission is valid but incorrect (infeasible, etc)

• 2: Submission is correct but not being accepted.

int MDOcbsolution(void *cbdata, const double *solution, double *objP)

Provide a new feasible solution for a MIP model.

Parameters

• cbdata (void*) – [in] The cbdata argument passed into user callback function.

• solution (const double*) – [in] The new feasible solution to be provided.

• objP (double*) – [out] The place to hold objective value for new provided solution.

Returns

A zero or negative response code that specifies the status of the function, otherwise a positive number to indicate the submission status:

• 1: Submission is valid but incorrect (infeasible, etc)

• 2: Submission is correct but not being accepted.