Math::GSL::ODEIV - functions for solving ordinary differential equation (ODE) initial value problems
use Math::GSL::ODEIV qw /:all/;
Here is a list of all the functions in this module :
gsl_odeiv_step_alloc($T,
$dim) - This function returns a pointer to a newly allocated instance of a stepping function of type $T for a system of $dim dimensions.$T must be one of the step type constant above.gsl_odeiv_step_reset($s) - This function resets the stepping function $s.
It should be used whenever the next use of s will not be a continuation of a previous step.gsl_odeiv_step_free($s) - This function frees all the memory associated with the stepping function $s.gsl_odeiv_step_name($s) - This function returns a pointer to the name of the stepping function.gsl_odeiv_step_order($s) - This function returns the order of the stepping function on the previous step.
This order can vary if the stepping function itself is adaptive.gsl_odeiv_step_apply gsl_odeiv_control_alloc($T) - This function returns a pointer to a newly allocated instance of a control function of type $T.
This function is only needed for defining new types of control functions.
For most purposes the standard control functions described above should be sufficient.
$T is a gsl_odeiv_control_type.gsl_odeiv_control_init($c,
$eps_abs,
$eps_rel,
$a_y,
$a_dydt) - This function initializes the control function c with the parameters eps_abs (absolute error),
eps_rel (relative error),
a_y (scaling factor for y) and a_dydt (scaling factor for derivatives).gsl_odeiv_control_free gsl_odeiv_control_hadjust gsl_odeiv_control_name gsl_odeiv_control_standard_new($eps_abs,
$eps_rel,
$a_y,
$a_dydt) - The standard control object is a four parameter heuristic based on absolute and relative errors $eps_abs and $eps_rel,
and scaling factors $a_y and $a_dydt for the system state y(t) and derivatives y'(t) respectively.
The step-size adjustment procedure for this method begins by computing the desired error level D_i for each component,
D_i = eps_abs + eps_rel * (a_y |y_i| + a_dydt h |y'_i|) and comparing it with the observed error E_i = |yerr_i|.
If the observed error E exceeds the desired error level D by more than 10% for any component then the method reduces the step-size by an appropriate factor,
h_new = h_old * S * (E/D)^(-1/q) where q is the consistency order of the method (e.g.
q=4 for 4(5) embedded RK),
and S is a safety factor of 0.9.
The ratio E/D is taken to be the maximum of the ratios E_i/D_i.
If the observed error E is less than 50% of the desired error level D for the maximum ratio E_i/D_i then the algorithm takes the opportunity to increase the step-size to bring the error in line with the desired level,
h_new = h_old * S * (E/D)^(-1/(q+1)) This encompasses all the standard error scaling methods.
To avoid uncontrolled changes in the stepsize,
the overall scaling factor is limited to the range 1/5 to 5.gsl_odeiv_control_y_new($eps_abs,
$eps_rel) - This function creates a new control object which will keep the local error on each step within an absolute error of $eps_abs and relative error of $eps_rel with respect to the solution y_i(t).
This is equivalent to the standard control object with a_y=1 and a_dydt=0.gsl_odeiv_control_yp_new($eps_abs,
$eps_rel) - This function creates a new control object which will keep the local error on each step within an absolute error of $eps_abs and relative error of $eps_rel with respect to the derivatives of the solution y'_i(t).
This is equivalent to the standard control object with a_y=0 and a_dydt=1.gsl_odeiv_control_scaled_new($eps_abs,
$eps_rel,
$a_y,
$a_dydt,
$scale_abs,
$dim) - This function creates a new control object which uses the same algorithm as gsl_odeiv_control_standard_new but with an absolute error which is scaled for each component by the array reference $scale_abs.
The formula for D_i for this control object is,
D_i = eps_abs * s_i + eps_rel * (a_y |y_i| + a_dydt h |y'_i|) where s_i is the i-th component of the array scale_abs.
The same error control heuristic is used by the Matlab ode suite.gsl_odeiv_evolve_alloc($dim) - This function returns a pointer to a newly allocated instance of an evolution function for a system of $dim dimensions.gsl_odeiv_evolve_apply gsl_odeiv_evolve_reset($e) - This function resets the evolution function $e.
It should be used whenever the next use of $e will not be a continuation of a previous step.gsl_odeiv_evolve_free($e) - This function frees all the memory associated with the evolution function $e.This module also includes the following constants :
$GSL_ODEIV_HADJ_INC$GSL_ODEIV_HADJ_NIL$GSL_ODEIV_HADJ_DEC$gsl_odeiv_step_rk2 - Embedded Runge-Kutta (2,
3) method.$gsl_odeiv_step_rk4 - 4th order (classical) Runge-Kutta.
The error estimate is obtained by halving the step-size.
For more efficient estimate of the error,
use the Runge-Kutta-Fehlberg method described below.$gsl_odeiv_step_rkf45 - Embedded Runge-Kutta-Fehlberg (4,
5) method.
This method is a good general-purpose integrator.$gsl_odeiv_step_rkck - Embedded Runge-Kutta Cash-Karp (4,
5) method.$gsl_odeiv_step_rk8pd - Embedded Runge-Kutta Prince-Dormand (8,9) method.$gsl_odeiv_step_rk2imp - Implicit 2nd order Runge-Kutta at Gaussian points.$gsl_odeiv_step_rk2simp$gsl_odeiv_step_rk4imp - Implicit 4th order Runge-Kutta at Gaussian points.$gsl_odeiv_step_bsimp - Implicit Bulirsch-Stoer method of Bader and Deuflhard.
This algorithm requires the Jacobian.$gsl_odeiv_step_gear1 - M=1 implicit Gear method.$gsl_odeiv_step_gear2 - M=2 implicit Gear method.For more informations on the functions, we refer you to the GSL offcial documentation: http://www.gnu.org/software/gsl/manual/html_node/
Jonathan "Duke" Leto <jonathan@leto.net> and Thierry Moisan <thierry.moisan@gmail.com>
Copyright (C) 2008-2011 Jonathan "Duke" Leto and Thierry Moisan
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
