[Coin-discuss] Suggestions on how to go about tuning?

[Weiguo Liu]

Philip, 

I lost your original mail. 
But yes, if you have a good initial IP solution, you can guide CBC with your solution in hope that this is a "good footing". Certainly in general it is hard to find an "good" initial solution. Usually you can not tell if a heuristic solution is good or not. But you can always tell CBC the objective value of the solution in order to reduce the initial gap between lower and upper bounds. The performance of the B&B is largely affected by this gap. 
The other thing you may be able to do is when you know what is wrong with the CBC's initial solution. For example, one arc can never be in an optimization solution, then you can fix the variable (force this arc to be 0), before starts the branch and bound. 

Weiguo 


-----Original Message-----
From: coin-discuss-bounces at list.coin-or.org
[mailto:coin-discuss-bounces at list.coin-or.org]On Behalf Of Michael
Hennebry
Sent: Thursday, June 01, 2006 9:28 AM
To: Discussions about open source software for Operations Research
Subject: Re: [Coin-discuss] Suggestions on how to go about tuning?


On Wed, 31 May 2006 hpwalton at comcast.net wrote:

> I'm having a performance issue with a specific instance of data.  ...
>
> I'm thinking CBC just gets off on the wrong foot.  ...

The question is how should CBC find the correct foot?
Possibly the best way is to find an initial feasible
solution from a heuristic and tell CBC that you want
a solution at least that good.

Probably CBC has settable branch order parameters.

--
Mike   hennebry at web.cs.ndsu.NoDak.edu
"it stands to reason that they weren't always called the ancients."
                                                      --  Daniel Jackson

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