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1 /* |
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2 |
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3 Copyright (C) 1996, 1997 John W. Eaton |
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4 |
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5 This file is part of Octave. |
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6 |
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7 Octave is free software; you can redistribute it and/or modify it |
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8 under the terms of the GNU General Public License as published by the |
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9 Free Software Foundation; either version 2, or (at your option) any |
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10 later version. |
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11 |
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12 Octave is distributed in the hope that it will be useful, but WITHOUT |
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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15 for more details. |
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16 |
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17 You should have received a copy of the GNU General Public License |
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18 along with Octave; see the file COPYING. If not, write to the Free |
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19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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20 |
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21 */ |
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22 |
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23 #ifdef HAVE_CONFIG_H |
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24 #include <config.h> |
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25 #endif |
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26 |
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27 #include "CmplxLU.h" |
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28 #include "dbleLU.h" |
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29 |
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30 #include "defun-dld.h" |
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31 #include "error.h" |
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32 #include "gripes.h" |
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33 #include "oct-obj.h" |
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34 #include "utils.h" |
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35 |
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36 DEFUN_DLD (lu, args, nargout, |
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37 "-*- texinfo -*-\n\ |
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38 @deftypefn {Loadable Function} {[@var{l}, @var{u}, @var{p}] =} lu (@var{a})\n\ |
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39 @cindex LU decomposition\n\ |
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40 Compute the LU decomposition of @var{a}, using subroutines from\n\ |
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41 @sc{Lapack}. The result is returned in a permuted form, according to\n\ |
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42 the optional return value @var{p}. For example, given the matrix\n\ |
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43 @code{a = [1, 2; 3, 4]},\n\ |
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44 \n\ |
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45 @example\n\ |
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46 [l, u, p] = lu (a)\n\ |
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47 @end example\n\ |
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48 \n\ |
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49 @noindent\n\ |
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50 returns\n\ |
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51 \n\ |
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52 @example\n\ |
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53 l =\n\ |
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54 \n\ |
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55 1.00000 0.00000\n\ |
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56 0.33333 1.00000\n\ |
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57 \n\ |
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58 u =\n\ |
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59 \n\ |
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60 3.00000 4.00000\n\ |
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61 0.00000 0.66667\n\ |
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62 \n\ |
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63 p =\n\ |
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64 \n\ |
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65 0 1\n\ |
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66 1 0\n\ |
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67 @end example\n\ |
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68 @end deftypefn") |
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69 { |
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70 octave_value_list retval; |
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71 |
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72 int nargin = args.length (); |
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73 |
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74 if (nargin != 1 || nargout > 3) |
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75 { |
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76 print_usage ("lu"); |
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77 return retval; |
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78 } |
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79 |
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80 octave_value arg = args(0); |
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81 |
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82 int nr = arg.rows (); |
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83 int nc = arg.columns (); |
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84 |
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85 int arg_is_empty = empty_arg ("lu", nr, nc); |
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86 |
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87 if (arg_is_empty < 0) |
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88 return retval; |
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89 else if (arg_is_empty > 0) |
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90 return octave_value_list (3, Matrix ()); |
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91 |
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92 if (nr != nc) |
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93 { |
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94 gripe_square_matrix_required ("lu"); |
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95 return retval; |
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96 } |
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97 |
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98 if (arg.is_real_type ()) |
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99 { |
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100 Matrix m = arg.matrix_value (); |
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101 |
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102 if (! error_state) |
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103 { |
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104 LU fact (m); |
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105 |
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106 switch (nargout) |
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107 { |
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108 case 0: |
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109 case 1: |
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110 case 2: |
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111 { |
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112 Matrix P = fact.P (); |
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113 Matrix L = P.transpose () * fact.L (); |
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114 retval(1) = fact.U (); |
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115 retval(0) = L; |
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116 } |
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117 break; |
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118 |
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119 case 3: |
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120 default: |
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121 retval(2) = fact.P (); |
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122 retval(1) = fact.U (); |
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123 retval(0) = fact.L (); |
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124 break; |
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125 } |
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126 } |
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127 } |
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128 else if (arg.is_complex_type ()) |
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129 { |
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130 ComplexMatrix m = arg.complex_matrix_value (); |
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131 |
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132 if (! error_state) |
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133 { |
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134 ComplexLU fact (m); |
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135 |
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136 switch (nargout) |
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137 { |
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138 case 0: |
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139 case 1: |
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140 case 2: |
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141 { |
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142 ComplexMatrix P = fact.P (); |
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143 ComplexMatrix L = P.transpose () * fact.L (); |
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144 retval(1) = fact.U (); |
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145 retval(0) = L; |
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146 } |
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147 break; |
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148 |
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149 case 3: |
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150 default: |
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151 retval(2) = fact.P (); |
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152 retval(1) = fact.U (); |
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153 retval(0) = fact.L (); |
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154 break; |
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155 } |
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156 } |
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157 } |
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158 else |
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159 { |
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160 gripe_wrong_type_arg ("lu", arg); |
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161 } |
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162 |
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163 return retval; |
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164 } |
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165 |
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166 /* |
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167 ;;; Local Variables: *** |
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168 ;;; mode: C++ *** |
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169 ;;; End: *** |
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170 */ |
