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Re: [Help-glpk] Question - steps of GMPL problem parsing

From: glpk xypron
Subject: Re: [Help-glpk] Question - steps of GMPL problem parsing
Date: Sun, 11 Jul 2010 07:21:11 +0200

Hello Loreena,

parsing and solving of GMPL models is done in multiple phases:

Phase 1 - model section translation
The model section of the GMPL file is parsed and internal 
structures describing the different objects like variables,
constraints, expressions are created.
This phase is executed by function glp_mpl_read_model().

Phase 2 - data section translation
The data section of of the model file is used to intialize
parameters and sets. For the model file this phase is
executed by function glp_mpl_read_model(). For optional
data files this phase is executed by function glp_mpl_read_data().

Phase 3 - model generation
In this phase the statements and expressions of the model up
to the solve statement are evaluated. This phase is executed by 
function glp_mpl_generate().

Phase 4 - model building
The problem instance for the solver is created. This phase is 
executed by function glp_mpl_build_prob().

glp_mpl_build_prob() will fail if not preceded by a call to

Phase 5 - solving
The problem is solved calling one of the solver with the Simplex,
the interior point or the MIP solver.

Phase 6 - postsolving
The result of the solver is transferred to the GMPL variables
and constraints. All statements after the solve statement of 
the model file are executed. This pahse is executed by function

Best regards


-------- Original-Nachricht --------
> Datum: Sat, 10 Jul 2010 18:22:17 -0300
> Betreff: Re: [Help-glpk] Question

> HIiiii Xyprommm
> Saved my day,
> thank thank thank youuuuuuuuuuuuuuuuu[?]
> It worked and my functions also seems to work fine =) [?]
> After read the model and the data
> Could you explain me the reason I need this function:(according to example
> on glpk manual)
> *glp_mpl_generate*—generate the model ?
> This  function
> *glp_mpl_build_prob*—build problem instance from the
> model
> So why do I need the first function if the second already build my problem
> and gives me an LP problem?
> I was thinking that after read, i should create the LP problem straight
> away
> with this second function ..but not... [?]
> Best Regards
> Loreena

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