[Couenne] solution output / heuristics

[Pietro Belotti]

Hi Ina,

> 1) Does this mean that Couenne found a new AND better solution to the 
> incumbent, or just a new solution that might not be better?

It means that Couenne found a new and better solution.

> 2) I solved some instances and the only heuristics that found solutions 
> are 'Init Rounding NLP' and 'Couenne Rounding NLP'. Does Couenne only 
> use these 2 heuristics?

Yes, and actually they are the same heuristic, the "Init" version being 
something that is applied at the very beginning. Of course a solution can 
also be found after solving the LP relaxation (whose solution sometimes 
happens to be integer feasible), strong branching, etc.

A feasibility pump heuristic is available in trunk and stable/0.4, but it 
is quite time consuming. You can enable it with the option

feas_pump_heuristic yes

in the couenne.opt option file.

Regards,
Pietro

--
Pietro Belotti
Dept. of Mathematical Sciences
Clemson University
email: pbelott at clemson.edu
phone: 864-656-6765
web:   http://myweb.clemson.edu/~pbelott

On Tue, 26 Mar 2013, Liffey1986 at gmx.de wrote:

> Hi all,
>  
> in the output Couenne gives information whenever a solution is found 
> (Integer solution of xxx found by xxx).
> I have two questions about this:
>  
> 1) Does this mean that Couenne found a new AND better solution to the 
> incumbent, or just a new solution that might not be better?
>  
> 2) I solved some instances and the only heuristics that found solutions 
> are 'Init Rounding NLP' and 'Couenne Rounding NLP'. Does Couenne only 
> use these 2 heuristics?
>  
> Best, Ina