Mercurial > repos > public > sbplib
diff +time/Rungekutta.m @ 888:8732d6bd9890 feature/timesteppers
Add general Runge-Kutta class
- Add a general Runge-Kutta class which time integrates the solution based on coefficients obtained from a Butcher tableau
- Add butcher tableau which returns coefficents for the specified Runge-Kutta method
- Remove RungKutta4proper, since obsolete
author | Vidar Stiernström <vidar.stiernstrom@it.uu.se> |
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date | Thu, 15 Nov 2018 17:10:01 -0800 |
parents | |
children | 679f4ddd982f |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/+time/Rungekutta.m Thu Nov 15 17:10:01 2018 -0800 @@ -0,0 +1,46 @@ +classdef Rungekutta < time.Timestepper + properties + F % RHS of the ODE + k % Time step + t % Time point + v % Solution vector + n % Time level + scheme % The scheme used for the time stepping, e.g rk4, rk6 etc. + end + + + methods + % Timesteps v_t = F(v,t), using the specified RK method from t = t0 with + % timestep k and initial conditions v = v0 + function obj = Rungekutta(F, k, t0, v0, method) + default_arg('method',"rk4"); + obj.F = F; + obj.k = k; + obj.t = t0; + obj.v = v0; + obj.n = 0; + % TODO: method "rk4" is also implemented in the butcher tableau, but the rungekutta_4.m implementation + % might be slightly more efficient. Need to do some profiling before deciding whether or not to keep it. + if (method == "rk4") + obj.scheme = @time.rk.rungekutta_4; + else + % Extract the coefficients for the specified method + % used for the RK updates from the Butcher tableua. + [s,a,b,c] = time.rk.butcherTableau(method); + coeffs = struct('s',s,'a',a,'b',b,'c',c); + obj.scheme = @(v,t,dt,F) time.rk.rungekutta(v, t , dt, F, coeffs); + end + end + + function [v,t] = getV(obj) + v = obj.v; + t = obj.t; + end + + function obj = step(obj) + obj.v = obj.scheme(obj.v, obj.t, obj.k, obj.F); + obj.t = obj.t + obj.k; + obj.n = obj.n + 1; + end + end +end \ No newline at end of file