Mercurial > repos > public > sbplib

annotate +time/Rungekutta.m @ 932:3860dad28239 feature/timesteppers

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Remove unnecessary(?) arguments in Rungekutta.scheme.
author Martin Almquist <malmquist@stanford.edu>
date Mon, 03 Dec 2018 16:33:27 -0800
parents 384ca2331a12
children 34b3d092a4d0
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
1 classdef Rungekutta < time.Timestepper
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
2 properties
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
3 F % RHS of the ODE
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
4 dt % Time step
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
5 t % Time point
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
6 v % Solution vector
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
7 n % Time level
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
8 scheme % The scheme used for the time stepping, e.g rk4, rk6 etc.
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
9 coeffs % Butcher tableau coefficients
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
10 V % All stage approximations in most recent time step
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
11 K % All stage rates in most recent time step
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
12 end
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
13
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
14
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
15 methods
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
16 % Timesteps v_t = F(v,t), using the specified RK method from t = t0 with
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
17 % timestep dt and initial conditions v = v0
931
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
18 function obj = Rungekutta(F, dt, t0, v0, method, discreteData)
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
19 default_arg('method',"rk4");
931
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
20 default_arg('discreteData', []);
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
21 obj.F = F;
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
22 obj.dt = dt;
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
23 obj.t = t0;
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
24 obj.v = v0;
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
25 obj.n = 0;
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
26
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
27 % Extract the coefficients for the specified method
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
28 % used for the RK updates from the Butcher tableua.
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
29 [s,a,b,c] = time.rk.butcherTableau(method);
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
30 obj.coeffs = struct('s',s,'a',a,'b',b,'c',c);
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
31
931
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
32 if isempty(discreteData)
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
33 % TODO: method "rk4" is also implemented in the butcher tableau, but the rungekutta_4.m implementation
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
34 % might be slightly more efficient. Need to do some profiling before deciding whether or not to keep it.
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
35 if (method == "rk4")
932
3860dad28239 Remove unnecessary(?) arguments in Rungekutta.scheme.
Martin Almquist <malmquist@stanford.edu>
parents: 931
diff changeset
36 obj.scheme = @(v,t,n) time.rk.rungekutta_4(v ,t, dt, F);
931
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
37 else
932
3860dad28239 Remove unnecessary(?) arguments in Rungekutta.scheme.
Martin Almquist <malmquist@stanford.edu>
parents: 931
diff changeset
38 obj.scheme = @(v,t,n) time.rk.rungekutta(v, t, dt, F, obj.coeffs);
931
384ca2331a12 Make Rungekutta class allow for discrete data.
Martin Almquist <malmquist@stanford.edu>
parents: 918
diff changeset
39 end
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
40 else
932
3860dad28239 Remove unnecessary(?) arguments in Rungekutta.scheme.
Martin Almquist <malmquist@stanford.edu>
parents: 931
diff changeset
41 obj.scheme = @(v,t,n) time.rk.rungekuttaDiscreteData(v, t, dt, F, obj.coeffs, discreteData, n);
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
42 end
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
43 end
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
44
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
45 % v: Current solution
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
46 % t: Current time
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
47 % V: All stage approximations in most recent time step
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
48 % K: All stage rates in most recent time step
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
49 % T: Time points (corresponding to V and K) in most recent time step
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
50 function [v,t,V,T,K] = getV(obj)
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
51 v = obj.v;
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
52 t = obj.t;
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
53 V = obj.V;
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
54 K = obj.K;
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
55 T = obj.t + obj.dt*obj.coeffs.b;
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
56 end
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
57
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
58 function obj = step(obj)
932
3860dad28239 Remove unnecessary(?) arguments in Rungekutta.scheme.
Martin Almquist <malmquist@stanford.edu>
parents: 931
diff changeset
59 [obj.v, obj.V, obj.K] = obj.scheme(obj.v, obj.t, obj.n);
918
679f4ddd982f Add properties for stage approximations and stage rates in the Rungekutta class.
Martin Almquist <malmquist@stanford.edu>
parents: 888
diff changeset
60 obj.t = obj.t + obj.dt;
888
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
61 obj.n = obj.n + 1;
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
62 end
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
63 end
8732d6bd9890 Add general Runge-Kutta class
Vidar Stiernström <vidar.stiernstrom@it.uu.se>
parents:
diff changeset
64 end