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/* proxy1.c */
/***********************************************************************
* This code is part of GLPK (GNU Linear Programming Kit).
* Copyright (C) 2013, 2018 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 "ios.h"
#include "proxy.h"
void ios_proxy_heur(glp_tree *T)
{ glp_prob *prob;
int j, status;
double *xstar, zstar;
/* this heuristic is applied only once on the root level */
if (!(T->curr->level == 0 && T->curr->solved == 1))
goto done;
prob = glp_create_prob();
glp_copy_prob(prob, T->mip, 0);
xstar = xcalloc(1+prob->n, sizeof(double));
for (j = 1; j <= prob->n; j++)
xstar[j] = 0.0;
if (T->mip->mip_stat != GLP_FEAS)
status = proxy(prob, &zstar, xstar, NULL, 0.0,
T->parm->ps_tm_lim, 1);
else
{ double *xinit = xcalloc(1+prob->n, sizeof(double));
for (j = 1; j <= prob->n; j++)
xinit[j] = T->mip->col[j]->mipx;
status = proxy(prob, &zstar, xstar, xinit, 0.0,
T->parm->ps_tm_lim, 1);
xfree(xinit);
}
if (status == 0)
#if 0 /* 17/III-2016 */
glp_ios_heur_sol(T, xstar);
#else
{ /* sometimes the proxy heuristic reports a wrong solution, so
* make sure that the solution is really integer feasible */
int i, feas1, feas2, ae_ind, re_ind;
double ae_max, re_max;
glp_copy_prob(prob, T->mip, 0);
for (j = 1; j <= prob->n; j++)
prob->col[j]->mipx = xstar[j];
for (i = 1; i <= prob->m; i++)
{ GLPROW *row;
GLPAIJ *aij;
row = prob->row[i];
row->mipx = 0.0;
for (aij = row->ptr; aij != NULL; aij = aij->r_next)
row->mipx += aij->val * aij->col->mipx;
}
glp_check_kkt(prob, GLP_MIP, GLP_KKT_PE, &ae_max, &ae_ind,
&re_max, &re_ind);
feas1 = (re_max <= 1e-6);
glp_check_kkt(prob, GLP_MIP, GLP_KKT_PB, &ae_max, &ae_ind,
&re_max, &re_ind);
feas2 = (re_max <= 1e-6);
if (feas1 && feas2)
glp_ios_heur_sol(T, xstar);
else
xprintf("WARNING: PROXY HEURISTIC REPORTED WRONG SOLUTION; "
"SOLUTION REJECTED\n");
}
#endif
xfree(xstar);
glp_delete_prob(prob);
done: return;
}
/* eof */
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