Re: [eclipse-clp-users] eplex: Unable to linearise / type error

Ulrich Scholz wrote:
> Dear all,
> 
> I try to write a CP problem with the eplex constraint solver.  Below you
> find my code.
> 
> I use decision variables to select one of a list of values.  On the call
> 
>   :- generateSubcomponents(3, S). 
> 
> I get the following error:
> 
> Eplex warning: Unable to linearise my_instance : Utility =:= [3, 1, 6] * [_184, _186, _188]
> type error in eplex : (my_instance : Utility =:= [3, 1, 6] * [_184, _186, _188])
> Abort
> 
> What to do?  
> 
> Is it a problem of my use of decision variables?  How to find an optimal
> solution in a discrete CSP?
> 
> 
> Thanks,
> 
> Ulrich
> 
> ------------
> :- lib(eplex_osi_clpcbc).
> :- eplex_instance(my_instance).
> 
> generateSubcomponent(NbImplementation, Subcomponent) :-
> 
>     % the decision variables
>     
>     length(DVs, NbImplementation),
>     my_instance: (DVs $:: 0..1),
>     my_instance: integers(DVs),
>     
>     % the utilities
>     
>     length(Utilities, NbImplementation),
>     
>     (foreach(Utility, Utilities)
>     do(
>           % results in an random Integer in the range [1, 8]
>           generateNoZeroRandom(8, Utility)
>       )
>     ),
>     
>     my_instance: Utility $= Utilities * DVs,
>     
>     Subcomponent = [Utility, DVs, Utilities].
> --------------
> 
Hi,

You are not using the correct syntax -- you cannot simply use lists in 
expression. You have something in the form:

A =:= [3,1,6] * [X,Y,Z]

I assume what you want is:

A =:= 3*X + Y + 6*Z

This is standard syntax of Prolog, and is described in many Prolog 
textbooks, and also in the ECLiPSe manuals and tutorials. Most of the 
examples in

http://87.230.22.228/examples/index.html

shows how to process structured data (lists, matricies) to create the 
expressions/constraints you want.

Cheers,

Kish


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