COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/mip_cplex.cc @ 2226:0411ac8a2d87

Last change on this file since 2226:0411ac8a2d87 was 2226:0411ac8a2d87, checked in by athos, 13 years ago

MIP interface tested (and corrected) for cplex 9.0

File size: 3.6 KB
Line 
1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2006
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_MIP_CPLEX_CC
20#define LEMON_MIP_CPLEX_CC
21
22///\file
23///\brief Implementation of the LEMON-CPLEX mip solver interface.
24
25#include <lemon/mip_cplex.h>
26
27namespace lemon {
28 
29  MipCplex::MipCplex() {
30    //This is unnecessary: setting integrality constraints on
31    //variables will set this, too
32
33    ///\todo The constant CPXPROB_MIP is
34    ///called CPXPROB_MILP in later versions
35#if CPX_VERSION < 800
36    CPXchgprobtype( env,  lp, CPXPROB_MIP);
37#else
38    CPXchgprobtype( env,  lp, CPXPROB_MILP);
39#endif
40
41  }
42
43  void MipCplex::_colType(int i, MipCplex::ColTypes col_type){
44
45    // Note If a variable is to be changed to binary, a call to CPXchgbds
46    // should also be made to change the bounds to 0 and 1.
47
48    int indices[1];
49    indices[0]=i;
50    char ctype[1];
51    switch (col_type){
52      case LEMON_INTEGER:
53        ctype[0]=CPX_INTEGER;//'I'
54        break;
55      case REAL:
56        ctype[0]=CPX_CONTINUOUS ;//'C'
57        break;
58    default:;
59        //FIXME problem
60    }
61    CPXchgctype (env, lp, 1, indices, ctype);
62  }
63 
64  MipCplex::ColTypes MipCplex::_colType(int i){
65   
66    char ctype[1];
67    status = CPXgetctype (env, lp, ctype, i, i);
68    switch (ctype[0]){
69
70    case CPX_INTEGER:
71      return LEMON_INTEGER;
72    case CPX_CONTINUOUS:
73      return REAL;
74    default:
75      return REAL;//Error!
76    }
77
78  }
79 
80  LpCplex::SolveExitStatus MipCplex::_solve(){
81
82    status = CPXmipopt (env, lp);
83    if (status==0)
84      return SOLVED;
85    else
86      return UNSOLVED;
87
88  }
89
90
91  LpCplex::SolutionStatus MipCplex::_getMipStatus(){
92
93    int stat = CPXgetstat(env, lp);
94
95    //Fortunately, MIP statuses did not change for cplex 8.0
96    switch (stat)
97    {
98      case CPXMIP_OPTIMAL:
99        return OPTIMAL;
100        //This also exists in later issues
101        //    case CPXMIP_UNBOUNDED:
102        //return INFINITE;
103      case CPXMIP_INFEASIBLE:
104        return INFEASIBLE;
105      default:
106        return UNDEFINED;
107    }
108    //Unboundedness not treated well: the following is from cplex 9.0 doc
109    // About Unboundedness
110
111    // The treatment of models that are unbounded involves a few
112    // subtleties. Specifically, a declaration of unboundedness means that
113    // ILOG CPLEX has determined that the model has an unbounded
114    // ray. Given any feasible solution x with objective z, a multiple of
115    // the unbounded ray can be added to x to give a feasible solution
116    // with objective z-1 (or z+1 for maximization models). Thus, if a
117    // feasible solution exists, then the optimal objective is
118    // unbounded. Note that ILOG CPLEX has not necessarily concluded that
119    // a feasible solution exists. Users can call the routine CPXsolninfo
120    // to determine whether ILOG CPLEX has also concluded that the model
121    // has a feasible solution.
122     
123  } 
124
125  MipCplex::Value MipCplex::_getPrimal(int i){
126    Value x;
127    CPXgetmipx(env, lp, &x, i, i);
128    return x;
129  }
130 
131  MipCplex::Value MipCplex::_getPrimalValue(){
132    Value objval;
133    status = CPXgetmipobjval(env, lp, &objval);
134    return objval;
135  }
136} //END OF NAMESPACE LEMON
137
138#endif //END OF MIP_CPLEX_CC
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