1 | /* -*- C++ -*- |
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2 | * demo/lp_demo.cc - Part of LEMON, a generic C++ optimization library |
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3 | * |
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4 | * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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5 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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6 | * |
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7 | * Permission to use, modify and distribute this software is granted |
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8 | * provided that this copyright notice appears in all copies. For |
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9 | * precise terms see the accompanying LICENSE file. |
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10 | * |
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11 | * This software is provided "AS IS" with no warranty of any kind, |
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12 | * express or implied, and with no claim as to its suitability for any |
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13 | * purpose. |
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14 | * |
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15 | */ |
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16 | |
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17 | /// \ingroup demos |
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18 | /// \file |
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19 | /// \brief A program demonstrating the LEMON LP solver interface |
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20 | /// |
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21 | /// This program is a simple application of the LEMON LP solver |
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22 | /// interface: we formulate a linear programming (LP) problem and then |
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23 | /// solve it using the underlying solver (GLPK or CPLEX for |
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24 | /// example). For the detailed documentation of the LEMON LP solver |
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25 | /// interface read \ref lemon::LpSolverBase "this". |
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26 | /// |
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27 | /// \include lp_demo.cc |
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28 | |
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29 | #include <lemon/lp.h> |
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30 | |
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31 | #include <iostream> |
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32 | |
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33 | using namespace lemon; |
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34 | |
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35 | int main() |
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36 | { |
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37 | //The following example is taken from the documentation of the GLPK library. |
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38 | //See it in the GLPK reference manual and among the GLPK sample files (sample.c) |
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39 | |
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40 | //A default solver is taken |
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41 | Lp lp; |
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42 | typedef Lp::Row Row; |
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43 | typedef Lp::Col Col; |
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44 | |
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45 | |
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46 | std::cout<<"A program demonstrating the LEMON LP solver interface"<<std::endl; |
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47 | std::cout<<"Solver used: "<<default_solver_name<<std::endl; |
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48 | |
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49 | //This will be a maximization |
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50 | lp.max(); |
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51 | |
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52 | //We add coloumns (variables) to our problem |
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53 | Col x1 = lp.addCol(); |
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54 | Col x2 = lp.addCol(); |
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55 | Col x3 = lp.addCol(); |
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56 | |
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57 | //Constraints |
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58 | lp.addRow(x1+x2+x3 <=100); |
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59 | lp.addRow(10*x1+4*x2+5*x3<=600); |
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60 | lp.addRow(2*x1+2*x2+6*x3<=300); |
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61 | //Nonnegativity of the variables |
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62 | lp.colLowerBound(x1, 0); |
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63 | lp.colLowerBound(x2, 0); |
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64 | lp.colLowerBound(x3, 0); |
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65 | //Objective function |
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66 | lp.setObj(10*x1+6*x2+4*x3); |
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67 | |
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68 | //Call the routine of the underlying LP solver |
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69 | lp.solve(); |
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70 | |
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71 | //Print results |
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72 | if (lp.primalStatus()==LpSolverBase::OPTIMAL){ |
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73 | std::cout<<"Optimal solution found!"<<std::endl; |
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74 | printf("optimum value = %g; x1 = %g; x2 = %g; x3 = %g\n", |
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75 | lp.primalValue(), |
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76 | lp.primal(x1), lp.primal(x2), lp.primal(x3)); |
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77 | } |
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78 | else{ |
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79 | std::cout<<"Optimal solution not found!"<<std::endl; |
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80 | } |
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81 | |
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82 | //End of LEMON style code |
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83 | |
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84 | //Here comes the same problem written in C using GLPK API routines |
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85 | |
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86 | // LPX *lp; |
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87 | // int ia[1+1000], ja[1+1000]; |
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88 | // double ar[1+1000], Z, x1, x2, x3; |
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89 | // s1: lp = lpx_create_prob(); |
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90 | // s2: lpx_set_prob_name(lp, "sample"); |
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91 | // s3: lpx_set_obj_dir(lp, LPX_MAX); |
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92 | // s4: lpx_add_rows(lp, 3); |
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93 | // s5: lpx_set_row_name(lp, 1, "p"); |
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94 | // s6: lpx_set_row_bnds(lp, 1, LPX_UP, 0.0, 100.0); |
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95 | // s7: lpx_set_row_name(lp, 2, "q"); |
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96 | // s8: lpx_set_row_bnds(lp, 2, LPX_UP, 0.0, 600.0); |
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97 | // s9: lpx_set_row_name(lp, 3, "r"); |
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98 | // s10: lpx_set_row_bnds(lp, 3, LPX_UP, 0.0, 300.0); |
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99 | // s11: lpx_add_cols(lp, 3); |
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100 | // s12: lpx_set_col_name(lp, 1, "x1"); |
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101 | // s13: lpx_set_col_bnds(lp, 1, LPX_LO, 0.0, 0.0); |
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102 | // s14: lpx_set_obj_coef(lp, 1, 10.0); |
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103 | // s15: lpx_set_col_name(lp, 2, "x2"); |
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104 | // s16: lpx_set_col_bnds(lp, 2, LPX_LO, 0.0, 0.0); |
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105 | // s17: lpx_set_obj_coef(lp, 2, 6.0); |
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106 | // s18: lpx_set_col_name(lp, 3, "x3"); |
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107 | // s19: lpx_set_col_bnds(lp, 3, LPX_LO, 0.0, 0.0); |
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108 | // s20: lpx_set_obj_coef(lp, 3, 4.0); |
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109 | // s21: ia[1] = 1, ja[1] = 1, ar[1] = 1.0; /* a[1,1] = 1 */ |
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110 | // s22: ia[2] = 1, ja[2] = 2, ar[2] = 1.0; /* a[1,2] = 1 */ |
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111 | // s23: ia[3] = 1, ja[3] = 3, ar[3] = 1.0; /* a[1,3] = 1 */ |
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112 | // s24: ia[4] = 2, ja[4] = 1, ar[4] = 10.0; /* a[2,1] = 10 */ |
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113 | // s25: ia[5] = 3, ja[5] = 1, ar[5] = 2.0; /* a[3,1] = 2 */ |
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114 | // s26: ia[6] = 2, ja[6] = 2, ar[6] = 4.0; /* a[2,2] = 4 */ |
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115 | // s27: ia[7] = 3, ja[7] = 2, ar[7] = 2.0; /* a[3,2] = 2 */ |
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116 | // s28: ia[8] = 2, ja[8] = 3, ar[8] = 5.0; /* a[2,3] = 5 */ |
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117 | // s29: ia[9] = 3, ja[9] = 3, ar[9] = 6.0; /* a[3,3] = 6 */ |
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118 | // s30: lpx_load_matrix(lp, 9, ia, ja, ar); |
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119 | // s31: lpx_simplex(lp); |
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120 | // s32: Z = lpx_get_obj_val(lp); |
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121 | // s33: x1 = lpx_get_col_prim(lp, 1); |
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122 | // s34: x2 = lpx_get_col_prim(lp, 2); |
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123 | // s35: x3 = lpx_get_col_prim(lp, 3); |
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124 | // s36: printf("\nZ = %g; x1 = %g; x2 = %g; x3 = %g\n", Z, x1, x2, x3); |
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125 | // s37: lpx_delete_prob(lp); |
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126 | // return 0; |
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127 | |
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128 | return 0; |
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129 | } |
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