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1 ## Copyright (C) 1996 Auburn University. All rights reserved. |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} zgreduce (@var{sys}, @var{meps}) |
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21 ## Implementation of procedure REDUCE in (Emami-Naeini and Van Dooren, |
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22 ## Automatica, # 1982). |
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23 ## @end deftypefn |
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24 |
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25 function retsys = zgreduce (Asys, meps) |
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26 |
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27 ## SYS_INTERNAL accesses members of system data structure |
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28 |
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29 is_digital(Asys); # make sure it's pure digital/continuous |
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30 |
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31 exit_1 = 0; # exit_1 = 1 or 2 on exit of loop |
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32 |
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33 if(Asys.n + Asys.nz == 0) |
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34 exit_1 = 2; # there are no finite zeros |
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35 endif |
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36 |
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37 while (! exit_1) |
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38 [Q,R,Pi] = qr(Asys.d); # compress rows of D |
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39 Asys.d = Q'*Asys.d; |
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40 Asys.c = Q'*Asys.c; |
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41 |
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42 ## check row norms of Asys.d |
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43 [sig,tau] = zgrownorm(Asys.d,meps); |
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44 |
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45 ## disp("=======================================") |
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46 ## disp(["zgreduce: meps=",num2str(meps), ", sig=",num2str(sig), ... |
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47 ## ", tau=",num2str(tau)]) |
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48 ## sysout(Asys) |
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49 |
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50 if(tau == 0) |
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51 exit_1 = 1; # exit_1 - reduction complete and correct |
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52 else |
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53 Cb = Db = []; |
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54 if(sig) |
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55 Cb = Asys.c(1:sig,:); |
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56 Db = Asys.d(1:sig,:); |
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57 endif |
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58 Ct =Asys.c(sig+(1:tau),:); |
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59 |
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60 ## compress columns of Ct |
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61 [pp,nn] = size(Ct); |
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62 rvec = nn:-1:1; |
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63 [V,Sj,Pi] = qr(Ct'); |
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64 V = V(:,rvec); |
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65 [rho,gnu] = zgrownorm(Sj,meps); |
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66 |
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67 ## disp(["zgreduce: rho=",num2str(rho),", gnu=",num2str(gnu)]) |
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68 ## Cb |
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69 ## Db |
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70 ## Ct |
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71 ## Sj' |
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72 |
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73 if(rho == 0) |
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74 exit_1 = 1; # exit_1 - reduction complete and correct |
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75 elseif(gnu == 0) |
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76 exit_1 = 2; # there are no zeros at all |
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77 else |
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78 mu = rho + sig; |
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79 |
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80 ## update system with Q |
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81 M = [Asys.a , Asys.b ]; |
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82 [nn,mm] = size(Asys.b); |
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83 |
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84 pp = rows(Asys.d); |
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85 Vm =[V,zeros(nn,mm) ; zeros(mm,nn), eye(mm)]; |
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86 if(sig) |
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87 M = [M; Cb, Db]; |
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88 Vs =[V',zeros(nn,sig) ; zeros(sig,nn), eye(sig)]; |
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89 else |
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90 Vs = V'; |
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91 endif |
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92 ## disp("zgreduce: before transform: M="); |
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93 ## M |
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94 ## Vs |
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95 ## Vm |
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96 |
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97 M = Vs*M*Vm; |
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98 |
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99 ## disp("zgreduce: after transform: M="); |
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100 ## M |
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101 |
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102 ## disp("debugging code:") |
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103 ## Mtmp = [Asys.a Asys.b; Asys.c Asys.d] |
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104 ## Vl = [V', zeros(nn,mm); zeros(mm,nn),Q] |
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105 ## Vr =[V,zeros(nn,mm) ; zeros(mm,nn), eye(mm)]; |
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106 ## Mtmpf = Vl*Mtmp*Vr |
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107 |
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108 idx = 1:gnu; |
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109 jdx = nn + (1:mm); |
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110 sdx = gnu + (1:mu); |
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111 |
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112 Asys.a = M(idx,idx); |
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113 Asys.b = M(idx,jdx); |
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114 Asys.c = M(sdx,idx); |
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115 Asys.d = M(sdx,jdx); |
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116 |
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117 ## disp(["zgreduce: resulting system: nn =",num2str(nn)," mu=",num2str(mu)]) |
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118 ## sysout(Asys) |
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119 ## idx |
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120 ## jdx |
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121 ## sdx |
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122 endif |
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123 endif |
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124 endwhile |
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125 |
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126 ## disp(["zgreduce: while loop done: exit_1=",num2str(exit_1)]); |
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127 |
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128 if(exit_1 == 2) |
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129 ## there are no zeros at all! |
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130 Asys.a = Asys.b = Asys.c = []; |
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131 endif |
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132 |
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133 ## update dimensions |
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134 if(is_digital(Asys)) |
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135 Asys.nz = rows(Asys.a); |
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136 else |
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137 Asys.n = rows(Asys.a); |
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138 endif |
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139 |
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140 retsys = Asys; |
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141 |
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142 endfunction |
