[Coin-discuss] CBC applied to maximization problems

[Hart, William E]

Cool!  Thanks! 

> -----Original Message-----
> From: Laszlo Ladanyi [mailto:ladanyi at us.ibm.com] 
> Sent: Tuesday, December 02, 2008 8:53 PM
> To: Hart, William E
> Cc: Michael Hennebry; coin-discuss at list.coin-or.org; 
> fmargot at andrew.cmu.edu
> Subject: Re: [Coin-discuss] CBC applied to maximization problems
> 
> Francois has submitted code to print a warning message:
> 
>    if(objsense == -1) {
>      printf("### WARNING: CoinLpIO::readLp(): Maximization 
> problem reformulated as minimization\n");
>      objectiveOffset_ = -objectiveOffset_;
>    }
> 
> It has been committed to stable/2.3 and to trunk.
> 
> --Laci
> 
> On Tue, 2 Dec 2008, Hart, William E wrote:
> 
> >
> > Mike:
> >
> > But how does the wrapper know when to flip, if it's simply 
> being handed an LP file?  Do I need to parse the LP file 
> before CBC does?
> >
> > I can't think of a way of dealing with this that isn't kludgey.
> >
> > --Bill
> >
> >> -----Original Message-----
> >> From: Michael Hennebry [mailto:hennebry at web.cs.ndsu.nodak.edu]
> >> Sent: Tuesday, December 02, 2008 8:27 PM
> >> To: Hart, William E
> >> Cc: fmargot at andrew.cmu.edu; coin-discuss at list.coin-or.org
> >> Subject: Re: [Coin-discuss] CBC applied to maximization problems
> >>
> >> On Tue, 2 Dec 2008, Hart, William E wrote:
> >>
> >>> Here's my scenario.  I have a wrapper script that passes a
> >> LP or MPS file to CBC, and then parses the output.  The results of 
> >> this optimization process are then returned to the user.  The 
> >> confusing thing is that a user sees minimization results 
> when passed 
> >> a maximization problem.  Logically, it's identical, but 
> this will be 
> >> surprising and confusing to non-technical users.
> >>
> >> I think that the answer is to have the wrapper do the flipping.
> >> The wrapper can print the warning.
> >> The wrapper could also negate any output that needed negating.
> >>
> >>> If CBC/CoinLpIO simply printed a warning that this problem
> >> was being reformulated, that would be enough for me to correctly 
> >> parse the output.  (Working with the library directly, 
> this wouldn't 
> >> be an issue because I could check the max/min sense of the 
> original 
> >> problem...).
> >>
> >> --
> >> Michael   hennebry at web.cs.ndsu.NoDak.edu
> >> "Pessimist: The glass is half empty.
> >> Optimist:   The glass is half full.
> >> Engineer:   The glass is twice as big as it needs to be."
> >>
> >>
> >
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> >
> 
>