[Cbc] Cuts and Integer Solutions in CBC

Tue May 27 11:27:59 EDT 2008

Haroldo,

Made some changes and added another example addCuts.cpp.  Seems to work on
most problems as long as cuts reasonable.

John

  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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  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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  Cbc at list.coin-or.org
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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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