Mercurial > octave-nkf
view scripts/ode/private/starting_stepsize.m @ 20620:e5f36a7854a5
Remove fuzzy matching from odeset/odeget.
* levenshtein.cc: Deleted file.
* libinterp/corefcn/module.mk: Remove levenshtein.cc from build system.
* fuzzy_compare.m: Deleted file.
* scripts/ode/module.mk: Remove fuzzy_compare.m from build system
* odeget.m: Reword docstring. Use a persistent cellstr variable to keep track
of all options. Replace fuzzy_compare() calls with combination of strcmpi and
strncmpi. Report errors relative to function odeget rather than OdePkg.
Rewrite and extend BIST tests. Add input validation BIST tests.
* odeset.m: Reword docstring. Use a persistent cellstr variable to keep track
of all options. Replace fuzzy_compare() calls with combination of strcmpi and
strncmpi. Report errors relative to function odeset rather than OdePkg.
Use more meaningful variables names and create intermediate variables with
logical names to help make code readable. Remove interactive input when
multiple property names match and just issue an error. Rewrite BIST tests.
* ode_struct_value_check.m: Remove input checking for private function which
must always be invoked correctly by caller. Use intermediate variables opt and
val to make the code more understandable. Consolidate checks on values into
single if statements. Use 'val == fix (val)' to check for integer.
* __unimplemented__.m: Removed odeset, odeget, ode45 from list.
author | Rik <rik@octave.org> |
---|---|
date | Fri, 09 Oct 2015 12:03:23 -0700 |
parents | eb9e2d187ed2 |
children |
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## Copyright (C) 2013, Roberto Porcu' <roberto.porcu@polimi.it> ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 3 of the License, or (at ## your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} {@var{h} =} starting_stepsize (@var{order}, @var{@@fun}, @var{t0}, @var{x0}) ## ## This function file can be used to determine a good initial step for an ODE ## solver of order @var{order}. The algorithm is that one described in [1]. ## ## Second input argument, which is @var{@@fun}, is the function describing ## the differential equations, @var{t0} is the initial time and @var{x0} is ## the initial condition. ## ## This function returns a good guess for the initial timestep @var{h}. ## ## References: ## [1] E. Hairer, S.P. Norsett and G. Wanner, ## "Solving Ordinary Differential Equations I: Nonstiff Problems", Springer. ## @end deftypefn ## ## @seealso{odepkg} function h = starting_stepsize (order, func, t0, x0, AbsTol, RelTol, normcontrol) ## compute norm of initial conditions d0 = AbsRel_Norm (x0, x0, AbsTol, RelTol, normcontrol); ## compute norm of the function evaluated at initial conditions y = func (t0, x0); d1 = AbsRel_Norm (y, y, AbsTol, RelTol, normcontrol); if (d0 < 1e-5 || d1 < 1e-5) h0 = 1e-6; else h0 = .01 * (d0 / d1); endif ## compute one step of Explicit-Euler x1 = x0 + h0 * y; ## approximate the derivative norm d2 = (1 / h0) * ... AbsRel_Norm (func (t0+h0, x1) - y, func (t0+h0, x1) - y, AbsTol, RelTol, normcontrol); if (max(d1, d2) <= 1e-15) h1 = max (1e-6, h0*1e-3); else h1 = (1e-2 / max (d1, d2)) ^(1 / (order+1)); endif h = min (100*h0, h1); endfunction