[Cbc] Documentation; Warmstart; Timelimit

[John Forrest]

Mona,

On 06/11/15 13:45, Mona Rahn wrote:
> Hi!
>
> I have three questions:
>
> 1) I am pretty new in using CBC with C++. Do you have a tip on a good 
> way to start, i.e. a documentation / tutorial / handbook for 
> beginners? Most of the stuff I found online was aimed at a much higher 
> level of knowledge. The documentation link that can be found on the 
> COIN-OR website (https://projects.coin-or.org/Cbc at the bottom) 
> doesn't work.
>
Documentation has never been the strong point of Cbc.  It can be useful 
to invoke cbc and try ? and then look at individual options - see 2)

> 2) I have an minimization LP that I resolve several times with 
> different objectives. That is, I solve it, upper bound the unique 
> variable appearing in my first objective function to the calculated 
> value, and set another variable as my objective.
> Now, my question is: The solver appears to start from scratch every 
> time I call it, but I would like to keep the old solution and start 
> from there. Is there a way to do this? I have seen the warm start in 
> OsiCbcSolverinterface, but I am not sure how to use it.
>

If you do cbc and then mipstart?? you will see that you can save the 
solution from one run and then use it as an input solution to next.
> 3) I would like to have set a time limit that only stops the program 
> if there is already a solution found (which isn't necessarily 
> optimal), but not if it is still searching for a solution. The only 
> time limit I have found is CbcModel::setMaximumSeconds, but this stops 
> the program no matter what. Do you have a solution for this?
>

You may wish to use the drivers that allow you to call cbc as normal but 
with changes.  Look at driver6.cpp.  If you have a driver like that then 
you could check if you have a solution and then stop on time.  I would 
suggest modifying MyEventHandler3::event to check if event was 
treeStatus and solution found and too many seconds.

John Forrest
> Thanks a lot in advance.
>
> Kind regards,
> Mona
>
>
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