Re: [Help-glpk] Compatibility with AMPL suffixes to display properties of variables and constraints

[glpk xypron]

Hello Germán,

The GMPL language does not support suffixes.

Some sensitity information is provided by
glpsol --bounds filename

Introducing suffixes to GLPK has been proposed before,
but not implemented in the maintenance release.

An unofficial patched version of a last year GLPK release can be
checked out with subversion

svn co http://glpk.dyndns.org/svn/glpk/branches/glpk-4.38-dot/

It supports the following suffixes in the post solution phase:

variables
lb - lower bound
ub - upper bound
val - value
dual - dual value
basic - 1 if variable is basic

constraints
lb - lower bound
ub - upper bound
dual - dual value
value - value

You can use the suffix only on scalars:

set S := {0..10};
var x{S};
...
#legal
display x[3].lb;
printf x[3].dual;
#illegal
display x.lb;

To generate duals for MIP problems the integer variables are fixed
and an extra call to the simplex routine is executed.

It would be interesting to know which suffixes would be of most
value for your use of GLPK.

Best regards

Xypron

> I've a model in Mathprog which I'm solving using `glpsol` and using
> `display` statements to generate a custom output. In AMPL there is a list
> of
> suffixes that one can use to display different properties of variables and
> constraints. For example for a constraint the available suffixes are:
>         astatus   body     defvar   dinit
>         dinit0    dual     lb       lbs
>         lbs1      lbs2     ldual    lslack
>         no        relax    slack    sno
>         sstatus   status   ub       ubs
>         ubs1      ubs2     udual    uslack
> 
> So, for example, you can write:
>   display C.lb;
> 
> To display the lower bound of C.
> 
> Is there an equivalent functionality in Mathprog? The above syntax does
> not
> work.
> 
> Thank you.
> 
> Regards,
> Germán.

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