[Cbc] Multi Solutions for an LP solve using CBC solver

[Ted Ralphs]

If I'm not missing something, your problem is an LP and Cbc would only
return alternative optimal solutions for MILPs. Regardless, the instance
you specified seems to have a unique optimum, both as an LP and an MILP.

Ted

On Tue, Mar 3, 2020 at 10:39 PM Aby Subin <aby.subin at nutanix.com> wrote:

> Thanks Haroldo for the reply. But here, even pre-processing was turned off
> ( along with cut and heuristics) . Please refer the commands those were
> executed which are mentioned in original message. So, was expecting more
> solutions. Could you tell if I am doing something wrong here?
>
> Regards
> Aby
>
> Get Outlook for iOS <https://aka.ms/o0ukef>
> ------------------------------
> *From:* Haroldo Gambini Santos <haroldo at ufop.edu.br>
> *Sent:* Tuesday, March 3, 2020 11:11:02 PM
> *To:* Aby Subin <aby.subin at nutanix.com>; cbc at list.coin-or.org <
> cbc at list.coin-or.org>
> *Subject:* Re: [Cbc] Multi Solutions for an LP solve using CBC solver
>
> Hi,
>
> This options saves multiple solutions IF in the search process they are
> found.
>
> In this case pre-processing already finds the optimal one, so the search
> stops.
>
> Em 3/1/20 1:57 PM, Aby Subin escreveu:
> > Hi all,
> >
> > As per the
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__list.coin-2Dor.org_pipermail_cbc_2012-2DFebruary_000766.html&d=DwIDaQ&c=s883GpUCOChKOHiocYtGcg&r=Bak3-3UtIw0QEwx645L7Agnx0N5k3avy8k01f01AiGY&m=d21DVhe16ObDeSF_FYf8vkL9Kd-QLsztSlwrxN_lkEk&s=Sd9g8RxyAgAmqFLNH-DxEQ22t7-XPhtuQLspqJtEqbw&e=
> , we
> > are supporting multiple solutions in CBC. But on trying out a
> > sample/test lp file, it is not working as expected
> > (tried with both disabling and enablign options for preprocessing,
> > heur, cutoff). The LP file content is as follows:
> > "
> >
> > \Problem name:
> >
> > Minimize
> >
> > obj: 2 x0 + 5 x1 + 3 x2
> >
> > Subject To
> >
> > cons0:x0 + x1 + x2 = 1
> >
> > Bounds
> >
> > 0 <= x0 <= 1
> >
> > 0 <= x1 <= 1
> >
> > 0 <= x2 <= 1
> >
> > End
> >
> >
> > "
> >
> >
> > I was testing the same using CBC shell command. The list of commands
> > tries out as follows
> >
> >
> > Coin:import test.lp
> >
> > Coin:maxSaved 3
> >
> > maxSavedSolutions was changed from 0 to 3
> >
> > Coin:cuts off
> >
> > Option for cutsOnOff changed from on to off
> >
> > Coin:heur off
> >
> > Option for heuristicsOnOff changed from on to off
> >
> > Coin:preprocess off
> >
> > Option for preprocess changed from sos to off
> >
> > Coin:solve
> >
> > Presolve 0 (-1) rows, 0 (-3) columns and 0 (-3) elements
> >
> > Empty problem - 0 rows, 0 columns and 0 elements
> >
> > Optimal - objective value 2
> >
> > After Postsolve, objective 2, infeasibilities - dual 0 (0), primal 0 (0)
> >
> > Optimal objective 2 - 0 iterations time 0.002, Presolve 0.00
> >
> > Coin:solu bestSol.txt
> >
> > Coin:nextB 1bestSol.txt
> >
> > All alternative solutions printed
> >
> >
> >
> > Could you please let me know on where I am missing the solutions?
> >
> >
> > Regards
> >
> > Aby
> >
> >
> > _______________________________________________
> > Cbc mailing list
> > Cbc at list.coin-or.org
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__list.coin-2Dor.org_mailman_listinfo_cbc&d=DwIDaQ&c=s883GpUCOChKOHiocYtGcg&r=Bak3-3UtIw0QEwx645L7Agnx0N5k3avy8k01f01AiGY&m=d21DVhe16ObDeSF_FYf8vkL9Kd-QLsztSlwrxN_lkEk&s=biVc2bYEu6InvhFCI-CnysgDsG-1PRjponTh4LZ1hZo&e=
>
> --
> =============================================================
> Haroldo Gambini Santos
> Computing Department
> Universidade Federal de Ouro Preto - UFOP
> email: haroldo at ufop.edu.br
> home/research page:
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.decom.ufop.br_haroldo&d=DwIDaQ&c=s883GpUCOChKOHiocYtGcg&r=Bak3-3UtIw0QEwx645L7Agnx0N5k3avy8k01f01AiGY&m=d21DVhe16ObDeSF_FYf8vkL9Kd-QLsztSlwrxN_lkEk&s=W8s7lsrnqrWfNnFykaiz33xwsKskK5foOFqUpkA28Vg&e=
>
>
> It has long been an axiom of mine that the little things are infinitely
> the most important.
> -- Sir Arthur Conan Doyle, "A Case of Identity"
>
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-- 
Dr. Ted Ralphs
Professor, Industrial and Systems Engineering
Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted
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