1 | /* $Id: CbcFathomDynamicProgramming.hpp 1573 2011-01-05 01:12:36Z lou $ */ |
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2 | // Copyright (C) 2004, International Business Machines |
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3 | // Corporation and others. All Rights Reserved. |
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4 | // This code is licensed under the terms of the Eclipse Public License (EPL). |
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5 | |
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6 | #ifndef CbcFathomDynamicProgramming_H |
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7 | #define CbcFathomDynamicProgramming_H |
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8 | |
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9 | #include "CbcFathom.hpp" |
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10 | |
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11 | //############################################################################# |
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12 | /** FathomDynamicProgramming class. |
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13 | |
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14 | The idea is that after some branching the problem will be effectively smaller than |
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15 | the original problem and maybe there will be a more specialized technique which can completely |
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16 | fathom this branch quickly. |
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17 | |
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18 | This is a dynamic programming implementation which is very fast for some |
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19 | specialized problems. It expects small integral rhs, an all integer problem |
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20 | and positive integral coefficients. At present it can not do general set covering |
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21 | problems just set partitioning. It can find multiple optima for various rhs |
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22 | combinations. |
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23 | |
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24 | The main limiting factor is size of state space. Each 1 rhs doubles the size of the problem. |
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25 | 2 or 3 rhs quadruples, 4,5,6,7 by 8 etc. |
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26 | */ |
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27 | |
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28 | class CbcFathomDynamicProgramming : public CbcFathom { |
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29 | public: |
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30 | // Default Constructor |
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31 | CbcFathomDynamicProgramming (); |
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32 | |
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33 | // Constructor with model - assumed before cuts |
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34 | CbcFathomDynamicProgramming (CbcModel & model); |
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35 | // Copy constructor |
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36 | CbcFathomDynamicProgramming(const CbcFathomDynamicProgramming & rhs); |
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37 | |
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38 | virtual ~CbcFathomDynamicProgramming(); |
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39 | |
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40 | /// update model (This is needed if cliques update matrix etc) |
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41 | virtual void setModel(CbcModel * model); |
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42 | |
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43 | /// Clone |
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44 | virtual CbcFathom * clone() const; |
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45 | |
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46 | /// Resets stuff if model changes |
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47 | virtual void resetModel(CbcModel * model); |
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48 | |
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49 | /** returns 0 if no fathoming attempted, 1 fully fathomed , |
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50 | 2 incomplete search, 3 incomplete search but treat as complete. |
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51 | If solution then newSolution will not be NULL and |
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52 | will be freed by CbcModel. It is expected that the solution is better |
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53 | than best so far but CbcModel will double check. |
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54 | |
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55 | If returns 3 then of course there is no guarantee of global optimum |
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56 | */ |
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57 | virtual int fathom(double *& newSolution); |
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58 | |
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59 | /// Maximum size allowed |
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60 | inline int maximumSize() const { |
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61 | return maximumSizeAllowed_; |
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62 | } |
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63 | inline void setMaximumSize(int value) { |
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64 | maximumSizeAllowed_ = value; |
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65 | } |
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66 | /// Returns type of algorithm and sets up arrays |
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67 | int checkPossible(int allowableSize = 0); |
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68 | // set algorithm |
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69 | inline void setAlgorithm(int value) { |
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70 | algorithm_ = value; |
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71 | } |
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72 | /** Tries a column |
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73 | returns true if was used in making any changes. |
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74 | */ |
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75 | bool tryColumn(int numberElements, const int * rows, |
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76 | const double * coefficients, double cost, |
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77 | int upper = COIN_INT_MAX); |
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78 | /// Returns cost array |
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79 | inline const double * cost() const { |
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80 | return cost_; |
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81 | } |
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82 | /// Returns back array |
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83 | inline const int * back() const { |
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84 | return back_; |
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85 | } |
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86 | /// Gets bit pattern for target result |
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87 | inline int target() const { |
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88 | return target_; |
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89 | } |
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90 | /// Sets bit pattern for target result |
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91 | inline void setTarget(int value) { |
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92 | target_ = value; |
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93 | } |
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94 | private: |
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95 | /// Does deleteions |
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96 | void gutsOfDelete(); |
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97 | |
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98 | /** Adds one attempt of one column of type 0, |
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99 | returns true if was used in making any changes |
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100 | */ |
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101 | bool addOneColumn0(int numberElements, const int * rows, |
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102 | double cost); |
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103 | /** Adds one attempt of one column of type 1, |
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104 | returns true if was used in making any changes. |
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105 | At present the user has to call it once for each possible value |
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106 | */ |
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107 | bool addOneColumn1(int numberElements, const int * rows, |
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108 | const int * coefficients, double cost); |
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109 | /** Adds one attempt of one column of type 1, |
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110 | returns true if was used in making any changes. |
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111 | At present the user has to call it once for each possible value. |
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112 | This version is when there are enough 1 rhs to do faster |
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113 | */ |
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114 | bool addOneColumn1A(int numberElements, const int * rows, |
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115 | const int * coefficients, double cost); |
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116 | /// Gets bit pattern from original column |
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117 | int bitPattern(int numberElements, const int * rows, |
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118 | const int * coefficients); |
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119 | /// Gets bit pattern from original column |
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120 | int bitPattern(int numberElements, const int * rows, |
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121 | const double * coefficients); |
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122 | /// Fills in original column (dense) from bit pattern - returning number nonzero |
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123 | int decodeBitPattern(int bitPattern, int * values, int numberRows); |
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124 | |
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125 | protected: |
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126 | |
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127 | /// Size of states (power of 2 unless just one constraint) |
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128 | int size_; |
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129 | /** Type - 0 coefficients and rhs all 1, |
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130 | 1 - coefficients > 1 or rhs > 1 |
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131 | */ |
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132 | int type_; |
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133 | /// Space for states |
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134 | double * cost_; |
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135 | /// Which state produced this cheapest one |
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136 | int * back_; |
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137 | /// Some rows may be satisified so we need a lookup |
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138 | int * lookup_; |
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139 | /// Space for sorted indices |
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140 | int * indices_; |
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141 | /// Number of active rows |
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142 | int numberActive_; |
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143 | /// Maximum size allowed |
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144 | int maximumSizeAllowed_; |
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145 | /// Start bit for each active row |
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146 | int * startBit_; |
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147 | /// Number bits for each active row |
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148 | int * numberBits_; |
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149 | /// Effective rhs |
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150 | int * rhs_; |
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151 | /// Space for sorted coefficients |
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152 | int * coefficients_; |
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153 | /// Target pattern |
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154 | int target_; |
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155 | /// Number of Non 1 rhs |
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156 | int numberNonOne_; |
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157 | /// Current bit pattern |
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158 | int bitPattern_; |
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159 | /// Current algorithm |
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160 | int algorithm_; |
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161 | private: |
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162 | |
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163 | /// Illegal Assignment operator |
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164 | CbcFathomDynamicProgramming & operator=(const CbcFathomDynamicProgramming& rhs); |
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165 | |
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166 | }; |
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167 | |
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168 | #endif |
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169 | |
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