[Cbc] Cuts and Integer Solutions in CBC
John J Forrest
jjforre at us.ibm.com
Fri May 23 12:06:46 EDT 2008
Haroldo,
Will try and look into it. I forgot about the problem that strong
branching might find a solution.
There was an example in Cbc/examples - qmip2.cpp.
Anyway I will see if I can make up another example.
John Forrest
From: "Haroldo Santos" <haroldo.santos at gmail.com>
To: John J Forrest/Watson/IBM at IBMUS
Cc: cbc at list.coin-or.org, cbc-bounces at list.coin-or.org
Date: 05/23/2008 08:22 AM
Subject: Re: [Cbc] Cuts and Integer Solutions in CBC
John,
Tried using the setMustCallAgain(true) to my cut generator, but the problem
continues.
Haroldo
On Wed, May 21, 2008 at 7:05 AM, John J Forrest <jjforre at us.ibm.com> wrote:
Haroldo,
There may be bugs in the code but I think that you need to change some of
the options in the CbcCutGenerator before you pass it to Cbc. In
particular setMustCallAgain(true) will say keep adding cuts as long as
there are any.
The deafult will stop after a few passes, which is probably why you are
seeing what is happening.
John Forrest
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"Haroldo Santos" ---05/20/2008 09:23:52 AM---Hi All,"Haroldo Santos"
---05/20/2008 09:23:52 AM---Hi All,
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Subject:
Hi All,
I'm working with a MIP with an exponential number of constraints. To
define the problem we need this huge amount of rows.
So, I defined a cbcmodel with a small subset of these constraints and
added an specialization of CglCutGenerator to dynamically insert the
other rows, as needed.
However, in the first iterations cbcmodel finds an Integer solution and
stops the search, even if new cuts were added.
Note that these "cuts" are not cuts in the traditional way: they do not
cut fractional solutions. Instead, they define the problem.
Is there any way to tell cbc that if new cuts were added, it must
continue the search ?
I think that in CPLEX this can be done by the so called "lazy
constraints".
Best regards,
Haroldo
--
===============================================================
Haroldo Gambini Santos
http://www.ic.uff.br/~hsantos
hsantos at ic.uff.br
Instituto de Computacao - Universidade Federal Fluminense
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Haroldo Gambini Santos
http://www.ic.uff.br/~hsantos
hsantos at ic.uff.br
Instituto de Computacao - Universidade Federal Fluminense
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