[2420] | 1 | /* -*- C++ -*- |
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| 2 | * |
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| 3 | * This file is a part of LEMON, a generic C++ optimization library |
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| 4 | * |
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| 5 | * Copyright (C) 2003-2007 |
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| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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| 8 | * |
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| 9 | * Permission to use, modify and distribute this software is granted |
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| 10 | * provided that this copyright notice appears in all copies. For |
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| 11 | * precise terms see the accompanying LICENSE file. |
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| 12 | * |
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| 13 | * This software is provided "AS IS" with no warranty of any kind, |
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| 14 | * express or implied, and with no claim as to its suitability for any |
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| 15 | * purpose. |
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| 16 | * |
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| 17 | */ |
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| 18 | |
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| 19 | /// \ingroup demos |
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| 20 | /// \file |
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| 21 | /// \brief Solver for SAT problems. |
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| 22 | /// |
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| 23 | /// This demo progam solves the SAT problem, i.e. the boolean |
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| 24 | /// satisfiability problem. The problem in general case is |
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| 25 | /// NP-complete. |
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| 26 | /// |
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| 27 | /// The program uses an integer linear program solver. A <tt>{0, |
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| 28 | /// 1}</tt> variable is assigned to each boolean variable. The |
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| 29 | /// disjunctions are converted to linear inequalities as each negation |
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| 30 | /// is replaced with a substraction from one and each disjunction is |
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| 31 | /// converted to addition. The generated linear expression should be |
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| 32 | /// at least one. |
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| 33 | /// |
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| 34 | /// \include sat.cc |
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| 35 | |
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| 36 | #include <iostream> |
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| 37 | #include <fstream> |
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| 38 | #include <sstream> |
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| 39 | #include <string> |
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| 40 | |
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| 41 | #include <lemon/lp.h> |
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| 42 | |
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| 43 | using namespace std; |
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| 44 | using namespace lemon; |
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| 45 | |
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| 46 | |
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| 47 | int main(int argc, const char *argv[]) { |
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| 48 | if (argc != 2) { |
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| 49 | std::cerr << "The SAT solver demo" << std::endl << std::endl; |
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| 50 | std::cerr << "The parameter should be a filename" << std::endl; |
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| 51 | std::cerr << "Each line of the file should contain a bool expression:" |
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| 52 | << std::endl; |
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| 53 | std::cerr << " [not] <variable> [or [not] <variable>]..." << std::endl; |
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| 54 | std::cerr << "The program prints a feasible solution if it exists" |
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| 55 | << std::endl; |
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| 56 | return -1; |
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| 57 | } |
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| 58 | ifstream is(argv[1]); |
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| 59 | |
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| 60 | Mip mip; |
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| 61 | mip.max(); |
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| 62 | mip.obj(0); |
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| 63 | |
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| 64 | string line; |
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| 65 | while (getline(is, line)) { |
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| 66 | istringstream ls(line); |
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| 67 | |
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| 68 | Mip::Expr expr; |
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| 69 | |
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| 70 | |
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| 71 | string op; |
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| 72 | do { |
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| 73 | string var; |
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| 74 | bool neg = false; |
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| 75 | |
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| 76 | ls >> var; |
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| 77 | if (var == "not") { |
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| 78 | neg = true; |
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| 79 | ls >> var; |
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| 80 | } |
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| 81 | |
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| 82 | Mip::Col col = mip.colByName(var); |
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| 83 | |
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| 84 | if (col == INVALID) { |
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| 85 | col = mip.addCol(); |
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| 86 | mip.colName(col, var); |
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| 87 | mip.colLowerBound(col, 0); |
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| 88 | mip.colUpperBound(col, 1); |
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| 89 | mip.integer(col, true); |
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| 90 | } |
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| 91 | |
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| 92 | expr += (neg ? 1 - col : col); |
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| 93 | |
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| 94 | } while (ls >> op && op == "or"); |
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| 95 | if (ls) { |
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| 96 | std::cerr << "Wrong bool expression" << std::endl; |
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| 97 | return -1; |
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| 98 | } |
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| 99 | mip.addRow(expr >= 1); |
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| 100 | } |
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| 101 | |
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| 102 | mip.solve(); |
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| 103 | |
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| 104 | if (mip.mipStatus() == Mip::OPTIMAL) { |
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| 105 | for (Mip::ColIt it(mip); it != INVALID; ++it) { |
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| 106 | std::cout << mip.colName(it) << " = " |
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| 107 | << (mip.primal(it) == 1 ? "true" : "false") |
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| 108 | << std::endl; |
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| 109 | } |
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| 110 | } else { |
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| 111 | std::cout << "There is no feasible solution." << std::endl; |
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| 112 | } |
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| 113 | |
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| 114 | return 0; |
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| 115 | } |
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