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/* asnlp.c (convert assignment problem to LP) */
/***********************************************************************
* This code is part of GLPK (GNU Linear Programming Kit).
* Copyright (C) 2009-2016 Free Software Foundation, Inc.
* Written by Andrew Makhorin <mao@gnu.org>.
*
* GLPK is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GLPK 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 General Public
* License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GLPK. If not, see <http://www.gnu.org/licenses/>.
***********************************************************************/
#include "env.h"
#include "glpk.h"
/***********************************************************************
* NAME
*
* glp_asnprob_lp - convert assignment problem to LP
*
* SYNOPSIS
*
* int glp_asnprob_lp(glp_prob *P, int form, glp_graph *G, int names,
* int v_set, int a_cost);
*
* DESCRIPTION
*
* The routine glp_asnprob_lp builds an LP problem, which corresponds
* to the assignment problem on the specified graph G.
*
* RETURNS
*
* If the LP problem has been successfully built, the routine returns
* zero, otherwise, non-zero. */
int glp_asnprob_lp(glp_prob *P, int form, glp_graph *G, int names,
int v_set, int a_cost)
{ glp_vertex *v;
glp_arc *a;
int i, j, ret, ind[1+2];
double cost, val[1+2];
if (!(form == GLP_ASN_MIN || form == GLP_ASN_MAX ||
form == GLP_ASN_MMP))
xerror("glp_asnprob_lp: form = %d; invalid parameter\n",
form);
if (!(names == GLP_ON || names == GLP_OFF))
xerror("glp_asnprob_lp: names = %d; invalid parameter\n",
names);
if (v_set >= 0 && v_set > G->v_size - (int)sizeof(int))
xerror("glp_asnprob_lp: v_set = %d; invalid offset\n",
v_set);
if (a_cost >= 0 && a_cost > G->a_size - (int)sizeof(double))
xerror("glp_asnprob_lp: a_cost = %d; invalid offset\n",
a_cost);
ret = glp_check_asnprob(G, v_set);
if (ret != 0) goto done;
glp_erase_prob(P);
if (names) glp_set_prob_name(P, G->name);
glp_set_obj_dir(P, form == GLP_ASN_MIN ? GLP_MIN : GLP_MAX);
if (G->nv > 0) glp_add_rows(P, G->nv);
for (i = 1; i <= G->nv; i++)
{ v = G->v[i];
if (names) glp_set_row_name(P, i, v->name);
glp_set_row_bnds(P, i, form == GLP_ASN_MMP ? GLP_UP : GLP_FX,
1.0, 1.0);
}
if (G->na > 0) glp_add_cols(P, G->na);
for (i = 1, j = 0; i <= G->nv; i++)
{ v = G->v[i];
for (a = v->out; a != NULL; a = a->t_next)
{ j++;
if (names)
{ char name[50+1];
sprintf(name, "x[%d,%d]", a->tail->i, a->head->i);
xassert(strlen(name) < sizeof(name));
glp_set_col_name(P, j, name);
}
ind[1] = a->tail->i, val[1] = +1.0;
ind[2] = a->head->i, val[2] = +1.0;
glp_set_mat_col(P, j, 2, ind, val);
glp_set_col_bnds(P, j, GLP_DB, 0.0, 1.0);
if (a_cost >= 0)
memcpy(&cost, (char *)a->data + a_cost, sizeof(double));
else
cost = 1.0;
glp_set_obj_coef(P, j, cost);
}
}
xassert(j == G->na);
done: return ret;
}
/* eof */
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