[Cbc] lp file format

Mon Nov 13 08:29:24 EST 2017

Question 2:

Ok, so I understand you that in case one has an integer variable that only is to hold positive values (including zero), then the correct/best definition is (only)
GENERAL
I1

And, also, specifying the following is *not* necessary:
BOUNDS
0 <= I1

But one would often include a statement like
BOUNDS
I1 <= 10

From: Haroldo Santos [mailto:haroldo.santos at gmail.com]
Sent: mandag 13. november 2017 14:20
To: Bjørn Sigurd Johansen (Spider Solutions AS) <bjorn.sigurd.johansen at spidersolutions.no>
Cc: cbc at list.coin-or.org; cbc at coin-or.org
Subject: Re: [Cbc] lp file format

On Mon, Nov 13, 2017 at 10:41 AM, Bjørn Sigurd Johansen (Spider Solutions AS) <bjorn.sigurd.johansen at spidersolutions.no<mailto:bjorn.sigurd.johansen at spidersolutions.no>> wrote:
Thx  : )

Three modelling questions:

Question 1:  Is there any advantage in defining bounds in BOUNDS section rather than in SUBJECT TO section?  I.e. is one of the following preferred for an (integer and/or continuous) variable?

SUBJECT TO
I1>=0
I1<=10
------------------------- alternatively -------------------------
BOUNDS
0 <= I1 <= 10

I think that to define in bounds is better.

Question 2:  What is/is there any purpose of defining no bounds, i.e. using FREE in BOUNDS section, for integer variables?

BOUNDS
I1 FREE
Free variables can assume positive and negative values.

GENERAL
I1
------------------------- alternatively only -------------------------
GENERAL
I1

Question 3:  Is there any difference between the following two?
V1>=0
V1>=+0
(I have seen “+0” being used several places).

When saving LPs you'll probably see -0 +0  these are all zero. When saving the solution you'll probably see very small values (such 1e-12)  which are zero too but appear as small values due to the limited precision arithmetic.

Thanks in advance,
Bjorn

From: Haroldo Santos [mailto:haroldo.santos at gmail.com<mailto:haroldo.santos at gmail.com>]
Sent: mandag 13. november 2017 13:03
To: Bjørn Sigurd Johansen (Spider Solutions AS) <bjorn.sigurd.johansen at spidersolutions.no<mailto:bjorn.sigurd.johansen at spidersolutions.no>>
Cc: cbc at list.coin-or.org<mailto:cbc at list.coin-or.org>; cbc at coin-or.org<mailto:cbc at coin-or.org>
Subject: Re: [Cbc] lp file format

Hi,

I think that there is no cbc specific (more precisely Osi) LP format documentation. The LP file format was introduced in CPLEX and I think that CPLEX has the official documentation.

On Mon, Nov 13, 2017 at 5:54 AM, Bjørn Sigurd Johansen (Spider Solutions AS) <bjorn.sigurd.johansen at spidersolutions.no<mailto:bjorn.sigurd.johansen at spidersolutions.no>> wrote:
Hi!

Is there any description on the CBC lp file format available ?

Or may the Cplex format description at http://lpsolve.sourceforge.net/5.0/CPLEX-format.htm be used ?

Best,
Bjorn

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--
=============================================================
Haroldo Gambini Santos
Computing Department
Universidade Federal de Ouro Preto - UFOP
email: haroldo [at ] iceb.ufop.br<http://iceb.ufop.br>
home/research page: www.decom.ufop.br/haroldo<http://www.decom.ufop.br/haroldo/>

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"

--
=============================================================
Haroldo Gambini Santos
Computing Department
Universidade Federal de Ouro Preto - UFOP
email: haroldo [at ] iceb.ufop.br<http://iceb.ufop.br>
home/research page: www.decom.ufop.br/haroldo<http://www.decom.ufop.br/haroldo/>

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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