COIN-OR::LEMON - Graph Library

source: lemon-0.x/demo/lp_demo.cc @ 1641:77f6ab7ad66f

Last change on this file since 1641:77f6ab7ad66f was 1641:77f6ab7ad66f, checked in by Alpar Juttner, 14 years ago

Demos' documentations include the source.

File size: 4.2 KB
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1/* -*- C++ -*-
2 * demo/lp_demo.cc - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17/// \ingroup demos
18/// \file
19/// \brief A program demonstrating the LEMON LP solver interface
20///
21/// This program is a simple application of the LEMON LP solver
22/// interface: we formulate a linear programming (LP) problem and then
23/// solve it using the underlying solver (GLPK or CPLEX for
24/// example). For the detailed documentation of the LEMON LP solver
25/// interface read \ref lemon::LpSolverBase "this".
26///
27/// \include lp_demo.cc
28
29#include <lemon/lp.h>
30
31#include <iostream>
32
33using namespace lemon;
34
35int main()
36{     
37 //The following example is taken from the documentation of the GLPK library.
38 //See it in the GLPK reference manual and among the GLPK sample files (sample.c)
39
40  //A default solver is taken
41  Lp lp;
42  typedef Lp::Row Row;
43  typedef Lp::Col Col;
44 
45
46  std::cout<<"A program demonstrating the LEMON LP solver interface"<<std::endl;
47  std::cout<<"Solver used: "<<default_solver_name<<std::endl;
48
49  //This will be a maximization
50  lp.max();
51
52  //We add coloumns (variables) to our problem
53  Col x1 = lp.addCol();
54  Col x2 = lp.addCol();
55  Col x3 = lp.addCol();
56
57  //Constraints
58  lp.addRow(x1+x2+x3 <=100); 
59  lp.addRow(10*x1+4*x2+5*x3<=600); 
60  lp.addRow(2*x1+2*x2+6*x3<=300); 
61  //Nonnegativity of the variables
62  lp.colLowerBound(x1, 0);
63  lp.colLowerBound(x2, 0);
64  lp.colLowerBound(x3, 0);
65  //Objective function
66  lp.setObj(10*x1+6*x2+4*x3);
67 
68  //Call the routine of the underlying LP solver
69  lp.solve();
70
71  //Print results
72  if (lp.primalStatus()==LpSolverBase::OPTIMAL){
73    std::cout<<"Optimal solution found!"<<std::endl;
74    printf("optimum value = %g; x1 = %g; x2 = %g; x3 = %g\n",
75           lp.primalValue(),
76           lp.primal(x1), lp.primal(x2), lp.primal(x3));
77  }
78  else{
79    std::cout<<"Optimal solution not found!"<<std::endl;
80  }
81
82  //End of LEMON style code
83
84  //Here comes the same problem written in C using GLPK API routines
85
86//   LPX *lp;
87//       int ia[1+1000], ja[1+1000];
88//       double ar[1+1000], Z, x1, x2, x3;
89// s1:   lp = lpx_create_prob();
90// s2:   lpx_set_prob_name(lp, "sample");
91// s3:   lpx_set_obj_dir(lp, LPX_MAX);
92// s4:   lpx_add_rows(lp, 3);
93// s5:   lpx_set_row_name(lp, 1, "p");
94// s6:   lpx_set_row_bnds(lp, 1, LPX_UP, 0.0, 100.0);
95// s7:   lpx_set_row_name(lp, 2, "q");
96// s8:   lpx_set_row_bnds(lp, 2, LPX_UP, 0.0, 600.0);
97// s9:   lpx_set_row_name(lp, 3, "r");
98// s10:  lpx_set_row_bnds(lp, 3, LPX_UP, 0.0, 300.0);
99// s11:  lpx_add_cols(lp, 3);
100// s12:  lpx_set_col_name(lp, 1, "x1");
101// s13:  lpx_set_col_bnds(lp, 1, LPX_LO, 0.0, 0.0);
102// s14:  lpx_set_obj_coef(lp, 1, 10.0);
103// s15:  lpx_set_col_name(lp, 2, "x2");
104// s16:  lpx_set_col_bnds(lp, 2, LPX_LO, 0.0, 0.0);
105// s17:  lpx_set_obj_coef(lp, 2, 6.0);
106// s18:  lpx_set_col_name(lp, 3, "x3");
107// s19:  lpx_set_col_bnds(lp, 3, LPX_LO, 0.0, 0.0);
108// s20:  lpx_set_obj_coef(lp, 3, 4.0);
109// s21:  ia[1] = 1, ja[1] = 1, ar[1] =  1.0; /* a[1,1] =  1 */
110// s22:  ia[2] = 1, ja[2] = 2, ar[2] =  1.0; /* a[1,2] =  1 */
111// s23:  ia[3] = 1, ja[3] = 3, ar[3] =  1.0; /* a[1,3] =  1 */
112// s24:  ia[4] = 2, ja[4] = 1, ar[4] = 10.0; /* a[2,1] = 10 */
113// s25:  ia[5] = 3, ja[5] = 1, ar[5] =  2.0; /* a[3,1] =  2 */
114// s26:  ia[6] = 2, ja[6] = 2, ar[6] =  4.0; /* a[2,2] =  4 */
115// s27:  ia[7] = 3, ja[7] = 2, ar[7] =  2.0; /* a[3,2] =  2 */
116// s28:  ia[8] = 2, ja[8] = 3, ar[8] =  5.0; /* a[2,3] =  5 */
117// s29:  ia[9] = 3, ja[9] = 3, ar[9] =  6.0; /* a[3,3] =  6 */
118// s30:  lpx_load_matrix(lp, 9, ia, ja, ar);
119// s31:  lpx_simplex(lp);
120// s32:  Z = lpx_get_obj_val(lp);
121// s33:  x1 = lpx_get_col_prim(lp, 1);
122// s34:  x2 = lpx_get_col_prim(lp, 2);
123// s35:  x3 = lpx_get_col_prim(lp, 3);
124// s36:  printf("\nZ = %g; x1 = %g; x2 = %g; x3 = %g\n", Z, x1, x2, x3);
125// s37:  lpx_delete_prob(lp);
126//       return 0;
127
128  return 0;
129}
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