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/* minisat1.c (driver to MiniSat solver) */
/***********************************************************************
* This code is part of GLPK (GNU Linear Programming Kit).
*
* Copyright (C) 2011-2016 Andrew Makhorin, Department for Applied
* Informatics, Moscow Aviation Institute, Moscow, Russia. All rights
* reserved. E-mail: <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 "minisat.h"
#include "prob.h"
int glp_minisat1(glp_prob *P)
{ /* solve CNF-SAT problem with MiniSat solver */
solver *s;
GLPAIJ *aij;
int i, j, len, ret, *ind;
double sum;
#if 0 /* 04/IV-2016 */
/* check problem object */
if (P == NULL || P->magic != GLP_PROB_MAGIC)
xerror("glp_minisat1: P = %p; invalid problem object\n",
P);
#endif
if (P->tree != NULL)
xerror("glp_minisat1: operation not allowed\n");
/* integer solution is currently undefined */
P->mip_stat = GLP_UNDEF;
P->mip_obj = 0.0;
/* check that problem object encodes CNF-SAT instance */
if (glp_check_cnfsat(P) != 0)
{ xprintf("glp_minisat1: problem object does not encode CNF-SAT "
"instance\n");
ret = GLP_EDATA;
goto done;
}
#if 0 /* 08/I-2017 by cmatraki */
#if 1 /* 07/XI-2015 */
if (sizeof(void *) != sizeof(int))
{ xprintf("glp_minisat1: sorry, MiniSat solver is not supported "
"on 64-bit platforms\n");
ret = GLP_EFAIL;
goto done;
}
#endif
#else
if (sizeof(void *) != sizeof(size_t))
{ xprintf("glp_minisat1: sorry, MiniSat solver is not supported "
"on this platform\n");
ret = GLP_EFAIL;
goto done;
}
#endif
/* solve CNF-SAT problem */
xprintf("Solving CNF-SAT problem...\n");
xprintf("Instance has %d variable%s, %d clause%s, and %d literal%"
"s\n", P->n, P->n == 1 ? "" : "s", P->m, P->m == 1 ? "" : "s",
P->nnz, P->nnz == 1 ? "" : "s");
/* if CNF-SAT has no clauses, it is satisfiable */
if (P->m == 0)
{ P->mip_stat = GLP_OPT;
for (j = 1; j <= P->n; j++)
P->col[j]->mipx = 0.0;
goto fini;
}
/* if CNF-SAT has an empty clause, it is unsatisfiable */
for (i = 1; i <= P->m; i++)
{ if (P->row[i]->ptr == NULL)
{ P->mip_stat = GLP_NOFEAS;
goto fini;
}
}
/* prepare input data for the solver */
s = solver_new();
solver_setnvars(s, P->n);
ind = xcalloc(1+P->n, sizeof(int));
for (i = 1; i <= P->m; i++)
{ len = 0;
for (aij = P->row[i]->ptr; aij != NULL; aij = aij->r_next)
{ ind[++len] = toLit(aij->col->j-1);
if (aij->val < 0.0)
ind[len] = lit_neg(ind[len]);
}
xassert(len > 0);
#if 0 /* 08/I-2017 by cmatraki */
xassert(solver_addclause(s, &ind[1], &ind[1+len]));
#else
if (!solver_addclause(s, &ind[1], &ind[1+len]))
{ /* found trivial conflict */
xfree(ind);
solver_delete(s);
P->mip_stat = GLP_NOFEAS;
goto fini;
}
#endif
}
xfree(ind);
/* call the solver */
s->verbosity = 1;
if (solver_solve(s, 0, 0))
{ /* instance is reported as satisfiable */
P->mip_stat = GLP_OPT;
/* copy solution to the problem object */
xassert(s->model.size == P->n);
for (j = 1; j <= P->n; j++)
{ P->col[j]->mipx =
s->model.ptr[j-1] == l_True ? 1.0 : 0.0;
}
/* compute row values */
for (i = 1; i <= P->m; i++)
{ sum = 0;
for (aij = P->row[i]->ptr; aij != NULL; aij = aij->r_next)
sum += aij->val * aij->col->mipx;
P->row[i]->mipx = sum;
}
/* check integer feasibility */
for (i = 1; i <= P->m; i++)
{ if (P->row[i]->mipx < P->row[i]->lb)
{ /* solution is wrong */
P->mip_stat = GLP_UNDEF;
break;
}
}
}
else
{ /* instance is reported as unsatisfiable */
P->mip_stat = GLP_NOFEAS;
}
solver_delete(s);
fini: /* report the instance status */
if (P->mip_stat == GLP_OPT)
{ xprintf("SATISFIABLE\n");
ret = 0;
}
else if (P->mip_stat == GLP_NOFEAS)
{ xprintf("UNSATISFIABLE\n");
ret = 0;
}
else
{ xprintf("glp_minisat1: solver failed\n");
ret = GLP_EFAIL;
}
done: return ret;
}
/* eof */
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