[Cmpl] A couple of questions

[Mike Steglich]

Hi Michal,

Do you want to use the CMPL sources or to you plan to execute CMPL as an external process?

As mentioned before in the second case you don't have any license problems. It is also possible to combine GPL-licensed and EPL-licensed binaries in one distribution if they are not derivative works.  I had a discussion in the OSI mailing list: http://projects.opensource.org/pipermail/license-discuss/2012-January/thread.html. In this case you don't have to publish the source code of your own software.

If you plan to use the CMPL source code than you need a license like LGPL or EPL for your purposes. It is possible that we grant an individual license for your project.  

Cheers

Mike


Am 02.02.2012 um 14:45 schrieb Michal Kaut:

> Hello Mike,
> 
> thanks for the answers.
> 
> Just a couple of comments:
> 
> 1) Good to see that you think that tupel-sets 'are a "must have" of a
> mathematical programming language'. (I have to work with Xpress and its
> designers do not share this belief, so I have to write things like
>  forall (i, j in NODES | exists(Cost(i, j))) do
> So, big thumb up for this one :-)
> 
> 2) Looks like the new data format will address my concerns, thanks.
> 
> 3) I do understand you reasons for liking GPL, but .. we I work at a company
> that delivers solutions to customers. As far as I understand the licenses, we
> could not combine CMPL and Cbc in one package and give/sell it to a customer, as
> the two licenses are not compatible.
> We could use GLPK as a solver, but it is significantly slower than Cbc for our
> problems. In addition, we can not always give away the source codes, which we
> would have to under GPL.
> 
> Anyway, I am looking forward to the new developments.
> 
> 
> Regards,
> Michal
> 
> 
> On 02.02.2012 13:07, Mike Steglich wrote:
>> Hi Michal,
>> 
>> Thank you for your interest in CMPL.
>> 
>> 1) Tupel-sets
>> We think also that tupel-sets (multi-dimensional sets)  are a "must have" of a
>> mathematical programming language. 
>> Therefore we are implementing tupel-sets and a new data file format at the moment.  
>> Please download a CMPL presentation (INFORMS 2011) that gives you an impression
>> about these new CMPL features (beginning at slide 12).
>> http://www.coliop.org/download/cmplInforms2011.pdf
>> 
>> I think (hope) that we will release this  version in April/May.
>> 
>> Until the release of the new version you can use a workaround.  The idea is to
>> have a matrix that contains the valid combinations of indices and to use this
>> matrix for the definition of the variables, objective function and the constraints. 
>> 
>> For the transportation problem I have defined a matrix /r/ for the valid routes
>> between the sources /i/ and the destinations /j/. 
>> r[,] := ( (1,1), (1,2) , (1,4), (2,2), (2,3) , (2,4), (3,1) , (3,3) );
>> The elements of/r/ are used for the definition of the variables/x[i,j]./
>> x[ r[i,1],r[i,2] ] 
>> The entire problem can be formulated as follows:
>> parameters:
>> plants  := 1(1)3;
>> centers := 1(1)4;
>> s[plants]  := (5000,6000,2500);
>> d[centers] := (6000,4000,2000,1500);
>> 
>> c[plants,centers] := ( (3,2,7,6), (7,5,2,3),(2,5,4,5) );
>> #relevant routes
>> r[,] := ( (1,1), (1,2) , (1,4), (2,2), (2,3) , (2,4), (3,1) , (3,3) );
>> 
>> variables:
>> #definition of the vector x is based on the relevant routes in r[,]
>> { i in defset(r[,1]) : x[ r[i,1],r[i,2] ]: real[0..]; }
>> 
>> objectives:
>> costs: sum{i in defset(r[,1]) : c[ r[i,1],r[i,2] ] * x[ r[i,1],r[i,2] ] } ->min;
>> 
>> constraints:
>> #extended by a check whether a x[i,j] is a valid route
>> supplies {i in plants  : sum{j in centers, count(x[i,j])>0 : x[i,j]  } <= s[i];}
>> demands  {j in centers : sum{i in plants,  count(x[i,j])>0 : x[i,j]  } =  d[j];} 
>> 
>> This is actually not a smart approach but it works.
>> 
>> 2) You are right, in CMPL all entities are declared and initiated at the same
>> moment. 
>> I assume that you want to implement and test a model independently from the
>> (real) data.  
>> Our idea is to create and test a model with dummy data. The values of the sets
>> and parameters can be read by using /include/ or /readcsv/() (and later with the
>> CMPL new data file format). 
>> For solving a real problem you only have to exchange the dummy date file by your
>> real data file.  
>> 
>> 3) GPL / EPL
>> This issue is (unfortunately) still under discussion. As you mentioned we have
>> got some requests in this mailing list that I answered directly and not via the
>> mailing list. I had also a discussion with Kipp Martin (COIN-OS).
>> 
>> We like the idea of "give and take" and we think that GPL is the best way to
>> share software in this manner.  But we see also the problem that GPL isn't
>> compatible to EPL and to commercial licenses if the source code is to be shared.
>> Therefore we are looking for approaches to avoid these problems. One alternative
>> is to have a dual license (GPL or EPL). The second possibility is to grant an
>> individual license to a specific project. 
>> 
>> But this issue is only relevant if you want to share source code.  If you only
>> want to use CMPL as an external process (e.g. via Java ProcessBuilder) then you
>> don' have any license problems.  
>> 
>> 
>> Cheers
>> 
>> Mike
>> 
>> 
>> Am 02.02.2012 um 09:58 schrieb Michal Kaut:
>> 
>>> Hello,
>>> 
>>> We are considering using CMPL (it looks very promising), but have a couple of
>>> questions first:
>>> 
>>> 1. Looking at the examples in the manual, I do not see any multi-dimensional
>>> sets. For example, in the Transportation problem, if we did not have all-to-all
>>> links, I would find it natural to define set 'links' being a subset of 'plants X
>>> centers' and index 'c' on that set. The objective would then be
>>> costs: sum{(i, j) in links : c[i,j] * x[i,j] } ­->min;
>>> Is this possible in CMPL?
>>> And if not, can I at least define c only on a subset of 'plants X centers'
>>> (without giving the subset a name)?
>>> 
>>> 2. As far as I can see, all entities are declared and initiated at once - does
>>> it mean that it is not possible to declare an entity (for ex. to say that S is a
>>> set), and give it values some time later?
>>> 
>>> 3. I guess you do not like this question, since you did not respond to it
>>> previously, but I try nevertheless: why GPL? Would you at least consider dual
>>> licensing with CPL or EPL, to make it compatible with the other Coin-OR projects?
>>> 
>>> 
>>> Thanks a lot in advance.
>>> 
>>> Regards,
>>> Michal Kaut
>>> _______________________________________________
>>> Cmpl mailing list
>>> Cmpl at list.coin-or.org <mailto:Cmpl at list.coin-or.org>
>>> http://list.coin-or.org/mailman/listinfo/cmpl
>> 
>> 
>> 
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