annotate scripts/optimization/fminbnd.m @ 16772:7eff3032d144

Fix seealso HTML links when using Texinfo 4.X (bug #38862). Use the prefix 'docX' instead of 'doc-' for Texinfo references. * doc/interpreter/arith.txi, doc/interpreter/basics.txi, doc/interpreter/container.txi, doc/interpreter/func.txi, doc/interpreter/java.txi, doc/interpreter/matrix.txi, doc/interpreter/munge-texi.pl, doc/interpreter/package.txi, doc/interpreter/plot.txi, doc/interpreter/stats.txi, doc/interpreter/strings.txi, doc/interpreter/system.txi, doc/interpreter/var.txi, doc/interpreter/vectorize.txi, libinterp/corefcn/qz.cc, libinterp/corefcn/regexp.cc, libinterp/interpfcn/error.cc, scripts/general/accumarray.m, scripts/general/structfun.m, scripts/miscellaneous/setfield.m, scripts/optimization/fminbnd.m, scripts/optimization/fzero.m, scripts/optimization/lsqnonneg.m: Use the prefix 'docX' instead of 'doc-' for Texinfo references.
author Rik <rik@octave.org>
date Tue, 18 Jun 2013 20:35:12 -0700
parents 242e9efd4315
children e39f00a32dc7
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72c96de7a403 maint: update copyright notices for 2012
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1 ## Copyright (C) 2008-2012 VZLU Prague, a.s.
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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 ## Author: Jaroslav Hajek <highegg@gmail.com>
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20
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21 ## -*- texinfo -*-
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22 ## @deftypefn {Function File} {[@var{x}, @var{fval}, @var{info}, @var{output}] =} fminbnd (@var{fun}, @var{a}, @var{b}, @var{options})
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23 ## Find a minimum point of a univariate function.
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24 ##
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25 ## @var{fun} should be a function handle or name. @var{a}, @var{b} specify a
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26 ## starting interval. @var{options} is a structure specifying additional
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27 ## options. Currently, @code{fminbnd} recognizes these options:
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28 ## "FunValCheck", "OutputFcn", "TolX", "MaxIter", "MaxFunEvals". For a
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29 ## description of these options, see @ref{docXoptimset,,optimset}.
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30 ##
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31 ## On exit, the function returns @var{x}, the approximate minimum point
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32 ## and @var{fval}, the function value thereof.
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33 ## @var{info} is an exit flag that can have these values:
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34 ##
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35 ## @itemize
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36 ## @item 1
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37 ## The algorithm converged to a solution.
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38 ##
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39 ## @item 0
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40 ## Maximum number of iterations or function evaluations has been exhausted.
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41 ##
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42 ## @item -1
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43 ## The algorithm has been terminated from user output function.
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44 ## @end itemize
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45 ##
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46 ## Notes: The search for a minimum is restricted to be in the interval
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47 ## bound by @var{a} and @var{b}. If you only have an initial point
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48 ## to begin searching from you will need to use an unconstrained
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49 ## minimization algorithm such as @code{fminunc} or @code{fminsearch}.
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50 ## @code{fminbnd} internally uses a Golden Section search strategy.
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51 ## @seealso{fzero, fminunc, fminsearch, optimset}
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52 ## @end deftypefn
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53
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54 ## This is patterned after opt/fmin.f from Netlib, which in turn is taken from
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55 ## Richard Brent: Algorithms For Minimization Without Derivatives, Prentice-Hall (1973)
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56
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57 ## PKG_ADD: ## Discard result to avoid polluting workspace with ans at startup.
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58 ## PKG_ADD: [~] = __all_opts__ ("fminbnd");
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59
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60 function [x, fval, info, output] = fminbnd (fun, xmin, xmax, options = struct ())
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61
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62 ## Get default options if requested.
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63 if (nargin == 1 && ischar (fun) && strcmp (fun, 'defaults'))
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64 x = optimset ("MaxIter", Inf, "MaxFunEvals", Inf, "TolX", 1e-8,
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65 "OutputFcn", [], "FunValCheck", "off");
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66 return;
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67 endif
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68
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69 if (nargin < 2 || nargin > 4)
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70 print_usage ();
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71 endif
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72
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73 if (ischar (fun))
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74 fun = str2func (fun, "global");
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75 endif
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76
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77 displ = optimget (options, "Display", "notify");
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78 funvalchk = strcmpi (optimget (options, "FunValCheck", "off"), "on");
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79 outfcn = optimget (options, "OutputFcn");
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80 tolx = optimget (options, "TolX", 1e-8);
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81 maxiter = optimget (options, "MaxIter", Inf);
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82 maxfev = optimget (options, "MaxFunEvals", Inf);
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83
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84 if (funvalchk)
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85 ## Replace fun with a guarded version.
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86 fun = @(x) guarded_eval (fun, x);
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87 endif
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88
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89 ## The default exit flag if exceeded number of iterations.
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90 info = 0;
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91 niter = 0;
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92 nfev = 0;
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93 sqrteps = eps (class (xmin + xmax));
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94
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95 c = 0.5*(3 - sqrt (5));
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96 a = xmin; b = xmax;
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97 v = a + c*(b-a);
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98 w = x = v;
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99 e = 0;
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100 fv = fw = fval = fun (x);
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101 nfev++;
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102
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103 ## Only for display purposes.
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104 iter(1).funccount = nfev;
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105 iter(1).x = x;
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106 iter(1).fx = fval;
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107
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108 while (niter < maxiter && nfev < maxfev)
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109 xm = 0.5*(a+b);
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110 ## FIXME: the golden section search can actually get closer than sqrt(eps)
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111 ## sometimes. Sometimes not, it depends on the function. This is the
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112 ## strategy from the Netlib code. Something yet smarter would be good.
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113 tol = 2 * sqrteps * abs (x) + tolx / 3;
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114 if (abs (x - xm) <= (2*tol - 0.5*(b-a)))
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115 info = 1;
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116 break;
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117 endif
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118
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119 if (abs (e) > tol)
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120 dogs = false;
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121 ## Try inverse parabolic step.
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122 iter(niter+1).procedure = "parabolic";
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123
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124 r = (x - w)*(fval - fv);
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125 q = (x - v)*(fval - fw);
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126 p = (x - v)*q - (x - w)*r;
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127 q = 2*(q - r);
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128 p *= -sign (q);
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129 q = abs (q);
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130 r = e;
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131 e = d;
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132
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133 if (abs (p) < abs (0.5*q*r) && p > q*(a-x) && p < q*(b-x))
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134 ## The parabolic step is acceptable.
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135 d = p / q;
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136 u = x + d;
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137
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138 ## f must not be evaluated too close to ax or bx.
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139 if (min (u-a, b-u) < 2*tol)
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140 d = tol * (sign (xm - x) + (xm == x));
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141 endif
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142 else
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143 dogs = true;
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144 endif
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145 else
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146 dogs = true;
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147 endif
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148 if (dogs)
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149 ## Default to golden section step.
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150
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151 ## WARNING: This is also the "initial" procedure following
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152 ## MATLAB nomenclature. After the loop we'll fix the string
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153 ## for the first step.
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154 iter(niter+1).procedure = "golden";
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155
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156 e = ifelse (x >= xm, a - x, b - x);
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157 d = c * e;
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158 endif
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159
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160 ## f must not be evaluated too close to x.
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161 u = x + max (abs (d), tol) * (sign (d) + (d == 0));
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162 fu = fun (u);
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163
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164 niter++;
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165
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166 iter(niter).funccount = nfev++;
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167 iter(niter).x = u;
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168 iter(niter).fx = fu;
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169
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170 ## update a, b, v, w, and x
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171
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172 if (fu <= fval)
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173 if (u < x)
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174 b = x;
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175 else
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176 a = x;
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177 endif
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178 v = w; fv = fw;
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179 w = x; fw = fval;
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180 x = u; fval = fu;
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181 else
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182 ## The following if-statement was originally executed even if fu == fval.
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183 if (u < x)
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184 a = u;
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185 else
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186 b = u;
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187 endif
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188 if (fu <= fw || w == x)
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189 v = w; fv = fw;
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190 w = u; fw = fu;
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191 elseif (fu <= fv || v == x || v == w)
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192 v = u;
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193 fv = fu;
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194 endif
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195 endif
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196
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197 ## If there's an output function, use it now.
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198 if (outfcn)
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199 optv.funccount = nfev;
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200 optv.fval = fval;
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201 optv.iteration = niter;
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202 if (outfcn (x, optv, "iter"))
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203 info = -1;
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204 break;
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205 endif
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206 endif
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207 endwhile
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208
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209 ## Fix the first step procedure.
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210 iter(1).procedure = "initial";
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211
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212 ## Handle the "Display" option
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213 switch displ
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214 case "iter"
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215 print_formatted_table (iter);
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216 print_exit_msg (info, struct("TolX", tolx, "fx", fval));
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217 case "notify"
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218 if (info == 0)
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219 print_exit_msg (info, struct("fx",fval));
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220 endif
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221 case "final"
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222 print_exit_msg (info, struct("TolX", tolx, "fx", fval));
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223 case "off"
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224 "skip";
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225 otherwise
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226 warning ("unknown option for Display: '%s'", displ);
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227 endswitch
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228
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229 output.iterations = niter;
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230 output.funcCount = nfev;
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diff changeset
231 output.bracket = [a, b];
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diff changeset
232 ## FIXME: bracketf possibly unavailable.
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233
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234 endfunction
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235
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236 ## An assistant function that evaluates a function handle and checks for
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237 ## bad results.
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238 function fx = guarded_eval (fun, x)
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239 fx = fun (x);
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240 fx = fx(1);
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241 if (! isreal (fx))
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242 error ("fminbnd:notreal", "fminbnd: non-real value encountered");
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243 elseif (isnan (fx))
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244 error ("fminbnd:isnan", "fminbnd: NaN value encountered");
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245 endif
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246 endfunction
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247
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248 ## A hack for printing a formatted table
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249 function print_formatted_table (table)
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250 printf ("\n Func-count x f(x) Procedure\n");
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251 for row=table
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252 printf("%5.5s %7.7s %8.8s\t%s\n",
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253 int2str (row.funccount), num2str (row.x,"%.5f"),
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254 num2str (row.fx,"%.6f"), row.procedure);
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255 endfor
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256 printf ("\n");
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257 endfunction
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258
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259 ## Print either a success termination message or bad news
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260 function print_exit_msg (info, opt=struct())
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261 printf ("");
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262 switch info
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263 case 1
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264 printf ("Optimization terminated:\n");
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265 printf (" the current x satisfies the termination criteria using OPTIONS.TolX of %e\n", opt.TolX);
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266 case 0
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267 printf ("Exiting: Maximum number of iterations has been exceeded\n");
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268 printf (" - increase MaxIter option.\n");
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269 printf (" Current function value: %.6f\n", opt.fx);
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270 case -1
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271 "FIXME"; ## FIXME: what's the message MATLAB prints for this case?
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272 otherwise
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273 error ("internal error - fminbnd() is bug, sorry!");
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274 endswitch
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275 printf ("\n");
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276 endfunction
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diff changeset
277
14363
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278
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279 %!shared opt0
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280 %! opt0 = optimset ("tolx", 0);
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281 %!assert (fminbnd (@cos, pi/2, 3*pi/2, opt0), pi, 10*sqrt (eps))
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282 %!assert (fminbnd (@(x) (x - 1e-3)^4, -1, 1, opt0), 1e-3, 10e-3*sqrt (eps))
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diff changeset
283 %!assert (fminbnd (@(x) abs (x-1e7), 0, 1e10, opt0), 1e7, 10e7*sqrt (eps))
f3d52523cde1 Use Octave coding conventions in all m-file %!test blocks
Rik <octave@nomad.inbox5.com>
parents: 14138
diff changeset
284 %!assert (fminbnd (@(x) x^2 + sin (2*pi*x), 0.4, 1, opt0), fzero (@(x) 2*x + 2*pi*cos (2*pi*x), [0.4, 1], opt0), sqrt (eps))
f3d52523cde1 Use Octave coding conventions in all m-file %!test blocks
Rik <octave@nomad.inbox5.com>
parents: 14138
diff changeset
285