1 | /* glpapi19.c (driver to MiniSat solver) */ |
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2 | |
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3 | /*********************************************************************** |
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4 | * This code is part of GLPK (GNU Linear Programming Kit). |
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5 | * |
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6 | * Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, |
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7 | * 2009, 2010, 2011 Andrew Makhorin, Department for Applied Informatics, |
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8 | * Moscow Aviation Institute, Moscow, Russia. All rights reserved. |
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9 | * E-mail: <mao@gnu.org>. |
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10 | * |
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11 | * GLPK is free software: you can redistribute it and/or modify it |
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12 | * under the terms of the GNU General Public License as published by |
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13 | * the Free Software Foundation, either version 3 of the License, or |
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14 | * (at your option) any later version. |
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15 | * |
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16 | * GLPK is distributed in the hope that it will be useful, but WITHOUT |
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17 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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18 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public |
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19 | * License for more details. |
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20 | * |
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21 | * You should have received a copy of the GNU General Public License |
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22 | * along with GLPK. If not, see <http://www.gnu.org/licenses/>. |
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23 | ***********************************************************************/ |
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24 | |
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25 | #include "glpapi.h" |
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26 | #include "minisat/minisat.h" |
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27 | |
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28 | int glp_minisat1(glp_prob *P) |
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29 | { /* solve CNF-SAT problem with MiniSat solver */ |
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30 | solver *s; |
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31 | GLPAIJ *aij; |
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32 | int i, j, len, ret, *ind; |
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33 | double sum; |
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34 | /* check problem object */ |
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35 | if (P == NULL || P->magic != GLP_PROB_MAGIC) |
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36 | xerror("glp_minisat1: P = %p; invalid problem object\n", |
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37 | P); |
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38 | if (P->tree != NULL) |
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39 | xerror("glp_minisat1: operation not allowed\n"); |
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40 | /* integer solution is currently undefined */ |
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41 | P->mip_stat = GLP_UNDEF; |
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42 | P->mip_obj = 0.0; |
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43 | /* check that problem object encodes CNF-SAT instance */ |
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44 | if (glp_check_cnfsat(P) != 0) |
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45 | { xprintf("glp_minisat1: problem object does not encode CNF-SAT " |
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46 | "instance\n"); |
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47 | ret = GLP_EDATA; |
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48 | goto done; |
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49 | } |
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50 | /* solve CNF-SAT problem */ |
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51 | xprintf("Solving CNF-SAT problem...\n"); |
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52 | xprintf("Instance has %d variable%s, %d clause%s, and %d literal%" |
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53 | "s\n", P->n, P->n == 1 ? "" : "s", P->m, P->m == 1 ? "" : "s", |
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54 | P->nnz, P->nnz == 1 ? "" : "s"); |
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55 | /* if CNF-SAT has no clauses, it is satisfiable */ |
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56 | if (P->m == 0) |
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57 | { P->mip_stat = GLP_OPT; |
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58 | for (j = 1; j <= P->n; j++) |
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59 | P->col[j]->mipx = 0.0; |
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60 | goto fini; |
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61 | } |
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62 | /* if CNF-SAT has an empty clause, it is unsatisfiable */ |
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63 | for (i = 1; i <= P->m; i++) |
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64 | { if (P->row[i]->ptr == NULL) |
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65 | { P->mip_stat = GLP_NOFEAS; |
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66 | goto fini; |
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67 | } |
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68 | } |
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69 | /* prepare input data for the solver */ |
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70 | s = solver_new(); |
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71 | solver_setnvars(s, P->n); |
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72 | ind = xcalloc(1+P->n, sizeof(int)); |
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73 | for (i = 1; i <= P->m; i++) |
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74 | { len = 0; |
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75 | for (aij = P->row[i]->ptr; aij != NULL; aij = aij->r_next) |
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76 | { ind[++len] = toLit(aij->col->j-1); |
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77 | if (aij->val < 0.0) |
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78 | ind[len] = lit_neg(ind[len]); |
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79 | } |
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80 | xassert(len > 0); |
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81 | xassert(solver_addclause(s, &ind[1], &ind[1+len])); |
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82 | } |
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83 | xfree(ind); |
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84 | /* call the solver */ |
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85 | s->verbosity = 1; |
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86 | if (solver_solve(s, 0, 0)) |
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87 | { /* instance is reported as satisfiable */ |
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88 | P->mip_stat = GLP_OPT; |
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89 | /* copy solution to the problem object */ |
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90 | xassert(s->model.size == P->n); |
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91 | for (j = 1; j <= P->n; j++) |
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92 | { P->col[j]->mipx = |
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93 | s->model.ptr[j-1] == l_True ? 1.0 : 0.0; |
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94 | } |
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95 | /* compute row values */ |
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96 | for (i = 1; i <= P->m; i++) |
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97 | { sum = 0; |
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98 | for (aij = P->row[i]->ptr; aij != NULL; aij = aij->r_next) |
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99 | sum += aij->val * aij->col->mipx; |
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100 | P->row[i]->mipx = sum; |
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101 | } |
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102 | /* check integer feasibility */ |
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103 | for (i = 1; i <= P->m; i++) |
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104 | { if (P->row[i]->mipx < P->row[i]->lb) |
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105 | { /* solution is wrong */ |
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106 | P->mip_stat = GLP_UNDEF; |
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107 | break; |
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108 | } |
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109 | } |
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110 | } |
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111 | else |
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112 | { /* instance is reported as unsatisfiable */ |
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113 | P->mip_stat = GLP_NOFEAS; |
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114 | } |
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115 | solver_delete(s); |
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116 | fini: /* report the instance status */ |
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117 | if (P->mip_stat == GLP_OPT) |
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118 | { xprintf("SATISFIABLE\n"); |
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119 | ret = 0; |
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120 | } |
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121 | else if (P->mip_stat == GLP_NOFEAS) |
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122 | { xprintf("UNSATISFIABLE\n"); |
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123 | ret = 0; |
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124 | } |
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125 | else |
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126 | { xprintf("glp_minisat1: solver failed\n"); |
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127 | ret = GLP_EFAIL; |
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128 | } |
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129 | done: return ret; |
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130 | } |
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131 | |
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132 | /* eof */ |
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