Originally posted by: lyxthe

Hello all,

I would like to know if a MIPStart can have some of the constraints violated, ie the MIPStart is infeasible. The aim is to itereate several solvings by beginning the first one without any constraints of a certain kind and incrementally add those that are violated such that finally have no violated constraints in the last loop without need to put all of them in the first solving loop.

I"m not sure I am very clear, but in the end I would like to know if I can give a MIPStart to cplex while some of the constraints violated. 

Thanks for the attention.

It seems that you want to do can be achieved by using lazy constraints. Maybe check them out in the user manual.

A MIP start can violate constraints. In that case CPLEX will of course reject the MIP start but will keep it and will potentially attempt to "repair" the infeasibility in the MIP start. Whether and how hard CPLEX attempts to repair infeasibility in a MIP start depends on the effor level of the MIP start, see here.

Originally posted by: VictorAS

Hi!

How do I recover the number of MIP starts that were deemed by CPLEX as having provided solutions? I passed successfully to CPLEX several MIP starts and after the solution process, I would like to report how many were accepted (so that I can compare the same set of experiments run with and without any MIP start). For example, look at the attachment, I want to recover the number 58 in the message 58 of 128 MIP starts provided solutions.

Thanks!

There is no API to get this number.

The only way to get this number is to parse the log output. Every API has a function to register a callback or stream through which the log is passed. For the callable library, look for CPXgetchannels() and CPXaddfuncdest(), for Concert look for IloCplex::setOut(), for Python look for Cplex.set_results_stream().

Originally posted by: VictorAS

Thank you, Daniel, I'll give a look at these functions for the callable library, which I am using.

Originally posted by: VictorAS

It worked. Now I am logging CPLEX output into a file.

Thanks for the hints!