COIN-OR::LEMON - Graph Library

source: lemon-0.x/demo/lp_demo.cc @ 1610:893dacc1866c

Last change on this file since 1610:893dacc1866c was 1610:893dacc1866c, checked in by Alpar Juttner, 14 years ago

A default LP solver is defined in lp.h

File size: 4.2 KB
Line 
1/* -*- C++ -*-
2 * demo/graph_to_eps.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 <lemon/lp.h>
28
29#include <iostream>
30
31using namespace lemon;
32
33int main()
34{     
35 //The following example is taken from the documentation of the GLPK library.
36 //See it in the GLPK reference manual and among the GLPK sample files (sample.c)
37
38  //A default solver is taken
39  Lp lp;
40  typedef Lp::Row Row;
41  typedef Lp::Col Col;
42 
43
44  std::cout<<"A program demonstrating the LEMON LP solver interface"<<std::endl;
45  std::cout<<"Solver used: "<<default_solver_name<<std::endl;
46
47  //This will be a maximization
48  lp.max();
49
50  //We add coloumns (variables) to our problem
51  Col x1 = lp.addCol();
52  Col x2 = lp.addCol();
53  Col x3 = lp.addCol();
54
55  //Constraints
56  lp.addRow(x1+x2+x3 <=100); 
57  lp.addRow(10*x1+4*x2+5*x3<=600); 
58  lp.addRow(2*x1+2*x2+6*x3<=300); 
59  //Nonnegativity of the variables
60  lp.colLowerBound(x1, 0);
61  lp.colLowerBound(x2, 0);
62  lp.colLowerBound(x3, 0);
63  //Objective function
64  lp.setObj(10*x1+6*x2+4*x3);
65 
66  //Call the routine of the underlying LP solver
67  lp.solve();
68
69  //Print results
70  if (lp.primalStatus()==LpSolverBase::OPTIMAL){
71    std::cout<<"Optimal solution found!"<<std::endl;
72    printf("optimum value = %g; x1 = %g; x2 = %g; x3 = %g\n",
73           lp.primalValue(),
74           lp.primal(x1), lp.primal(x2), lp.primal(x3));
75  }
76  else{
77    std::cout<<"Optimal solution not found!"<<std::endl;
78  }
79
80  //End of LEMON style code
81
82  //Here comes the same problem written in C using GLPK API routines
83
84//   LPX *lp;
85//       int ia[1+1000], ja[1+1000];
86//       double ar[1+1000], Z, x1, x2, x3;
87// s1:   lp = lpx_create_prob();
88// s2:   lpx_set_prob_name(lp, "sample");
89// s3:   lpx_set_obj_dir(lp, LPX_MAX);
90// s4:   lpx_add_rows(lp, 3);
91// s5:   lpx_set_row_name(lp, 1, "p");
92// s6:   lpx_set_row_bnds(lp, 1, LPX_UP, 0.0, 100.0);
93// s7:   lpx_set_row_name(lp, 2, "q");
94// s8:   lpx_set_row_bnds(lp, 2, LPX_UP, 0.0, 600.0);
95// s9:   lpx_set_row_name(lp, 3, "r");
96// s10:  lpx_set_row_bnds(lp, 3, LPX_UP, 0.0, 300.0);
97// s11:  lpx_add_cols(lp, 3);
98// s12:  lpx_set_col_name(lp, 1, "x1");
99// s13:  lpx_set_col_bnds(lp, 1, LPX_LO, 0.0, 0.0);
100// s14:  lpx_set_obj_coef(lp, 1, 10.0);
101// s15:  lpx_set_col_name(lp, 2, "x2");
102// s16:  lpx_set_col_bnds(lp, 2, LPX_LO, 0.0, 0.0);
103// s17:  lpx_set_obj_coef(lp, 2, 6.0);
104// s18:  lpx_set_col_name(lp, 3, "x3");
105// s19:  lpx_set_col_bnds(lp, 3, LPX_LO, 0.0, 0.0);
106// s20:  lpx_set_obj_coef(lp, 3, 4.0);
107// s21:  ia[1] = 1, ja[1] = 1, ar[1] =  1.0; /* a[1,1] =  1 */
108// s22:  ia[2] = 1, ja[2] = 2, ar[2] =  1.0; /* a[1,2] =  1 */
109// s23:  ia[3] = 1, ja[3] = 3, ar[3] =  1.0; /* a[1,3] =  1 */
110// s24:  ia[4] = 2, ja[4] = 1, ar[4] = 10.0; /* a[2,1] = 10 */
111// s25:  ia[5] = 3, ja[5] = 1, ar[5] =  2.0; /* a[3,1] =  2 */
112// s26:  ia[6] = 2, ja[6] = 2, ar[6] =  4.0; /* a[2,2] =  4 */
113// s27:  ia[7] = 3, ja[7] = 2, ar[7] =  2.0; /* a[3,2] =  2 */
114// s28:  ia[8] = 2, ja[8] = 3, ar[8] =  5.0; /* a[2,3] =  5 */
115// s29:  ia[9] = 3, ja[9] = 3, ar[9] =  6.0; /* a[3,3] =  6 */
116// s30:  lpx_load_matrix(lp, 9, ia, ja, ar);
117// s31:  lpx_simplex(lp);
118// s32:  Z = lpx_get_obj_val(lp);
119// s33:  x1 = lpx_get_col_prim(lp, 1);
120// s34:  x2 = lpx_get_col_prim(lp, 2);
121// s35:  x3 = lpx_get_col_prim(lp, 3);
122// s36:  printf("\nZ = %g; x1 = %g; x2 = %g; x3 = %g\n", Z, x1, x2, x3);
123// s37:  lpx_delete_prob(lp);
124//       return 0;
125
126  return 0;
127}
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