[Couenne] Accessing AMPL parameters

[Pietro Belotti]

Dear Pete,

> I am currently modifying Couenne, so that it can handle a multi-dimensional
> integral term,
> I want to manually obtain parameter values defined in the AMPL problem
> instance, ie. "param x := 1".
> Do you know how to access the data structure containing these values.

The "param" keyword introduces parameters for which no symbol table is  
passed by AMPL, at least to my knowledge. I believe you should use the  
"option" instruction in AMPL, but unfortunately this is not yet read  
by Couenne. With the AMPL command

option x 1;

you are creating a "parameter" that is passed to the solver, which can  
read it in a way similar to an option file. Couenne doesn't have such  
capability yet -- this actually just amount to adding a few lines that  
hook the option names available for use in the couenne.opt file to  
options usable in the AMPL code. I have little time for that now, but  
it's in the todo list.

> I am trying to avoid modifying the ASL library, by "hijacking" the MIN(x,y)
> function and using it
> to represent my integral function. The integral is defined by one variable,
> and many parameters,
> so the first argument is the variable, and the second argument is intended
> to point to a set of
> parameter values.

If I get this correctly, this is a momentary fix for the "param x :=  
1;" that is not working and the "option x 1;" that will (eventually)  
be implemented. You could indeed modify the exprMin so that its  
::operator() computes the value by referring to the first argument  
(referred to as arglist_ [0] -> Value ()). All other "options" can be  
accessed similarly with arglist_ [1] -> Value (), etc. At the moment I  
can't think of other methods you should change.

Hope this helps.

Cheers,
Pietro

_________________________________________
Pietro Belotti, Lehigh University
Dept. of Industrial & Systems Engineering
200 W Packer Ave, Bethlehem PA 18015.
phone: 610-758-3865   fax: 610-758-4886
email: belotti at lehigh.edu
web:   http://www.lehigh.edu/~pib208


On 01/04/2010, Pete Janes <ppjanes at gmail.com> wrote:

> Dear Pietro
>
> I am currently modifying Couenne, so that it can handle a multi-dimensional
> integral term,
> I want to manually obtain parameter values defined in the AMPL problem
> instance, ie. "param x := 1".
> Do you know how to access the data structure containing these values.
>
> I am trying to avoid modifying the ASL library, by "hijacking" the MIN(x,y)
> function and using it
> to represent my integral function. The integral is defined by one variable,
> and many parameters,
> so the first argument is the variable, and the second argument is intended
> to point to a set of
> parameter values.
>
> Do you know how I can solve this problem?
>
> Happy New Year,
>
> Pete


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