sc-fais-int.c

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/*
 
  $Id: sc-fais-int.c 1641 2016-03-02 08:20:19Z coelho $
 
  Copyright 1989-2016 MINES ParisTech
 
  This file is part of Linear/C3 Library.
 
  Linear/C3 Library is free software: you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  any later version.
 
  Linear/C3 Library is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE.
 
  See the GNU Lesser General Public License for more details.
 
  You should have received a copy of the GNU Lesser General Public License
  along with Linear/C3 Library.  If not, see <http://www.gnu.org/licenses/>.
 
*/
 
 /* package plint */
 
#ifdef HAVE_CONFIG_H
    #include "config.h"
#endif
 
#include <stdio.h>
#include <stdlib.h>
 
#include "boolean.h"
#include "arithmetique.h"
#include "vecteur.h"
#include "contrainte.h"
#include "sc.h"
 
#include "sommet.h"
#include "matrix.h"
 
#include "plint.h"
 
#define MALLOC(s,t,f) malloc(s)
 
/* bool sys_int_fais(Psysteme sys1):
 * Test de faisabilite d'un systeme lineaire syst1 en nombres entiers par 
 * l'algorithme des congruences decroissantes (cf. livre ???, pp. ??? ).
 * Renvoie true si le systeme est satisfiable (i.e. il definit un polyedre
 * convexe non vide), false sinon.
 *
 * Ce test est exact, mais il est tres couteux en temps CPU.
 *
 * Le systeme de contrainte syst1 n'est pas modifie
 */
bool sys_int_fais(sys1)
Psysteme sys1;
{
    Psysteme sys2 = NULL;
    Psommet fonct = fonct_min(sys1->dimension,sys1->base);
    Psolution sol1 = NULL;
 
    bool is_faisable = false;
 
    sys2=sc_dup(sys1);
    /*
     * Recherche d'une solution par l'algorithme des congruences
     * decroissantes a partir d'une fonction economique minimale (
     * recherche du minimum de la premiere variable du systeme)
     */
    if ((sys2 != NULL) && 
        ( (sys2->egalites != NULL) || (sys2->inegalites != NULL))) 
        sys2 = plint(sys2,fonct,&sol1);
    else
        is_faisable = true;
 
    if ((sys2 != NULL) && ((sys2->egalites != NULL)
                           || (sys2->inegalites != NULL)))
        is_faisable = true;
 
    if (is_faisable)
        /* cas ou le systeme est faisable          */
        sc_rm(sys2);
    return (is_faisable);
}