Basic customization

By customizing the controls for the XPRS_mse_defaulthandler callback (i.e., setting MSE_CALLBACKCULLSOLS_MIPOBJECT and/or MSE_CALLBACKCULLSOLS_DIVERSITY) the user can modify the behavior of the callback when the number of solutions exceeds the maximum. The user can delete p solutions based on the MIP objective values and then delete q of the remaining nMaxSols - p solutions based on the diversity metric (see below). The current solution will be rejected if it is no better than any of the solutions that were deleted. In this way the user has simple control of how the solution set is generated.

In addition to the MIP objective the MIP solution enumerator provides a metric for solutions based on the 'diversity' of the solution with respect to the other stored solutions. The diversity metric for a solution is the sum of difference metrics between the solution and the other stored solutions. By default the difference value between two solutions is calculated by the MIP solution enumerator using a simple difference metric that considers only the MIP entities in the solution. Note that for the MIP solution enumerator to calculate the diversity metrics a problem needs to be attached to the MIP solution pool (see 'Duplicate solutions'). This is because the global structure of the solution variables is required for the difference metric calculation. The user will typically attach to the MIP solution pool the XPRSprob to be used to run the enumeration. Finally, note that the user can provide their own difference metric calculation for solution pairs in a callback defined with a call to XPRS_mse_setcbgetsolutiondiff (in this case there does not need to be a problem attached to the MIP solution pool).