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comparison +rv/+time/RungekuttaExteriorRvMg.m @ 1160:76e3bb7836cf feature/rv

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First attempt at multi-grid calculation of the residual
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Tue, 25 Jun 2019 16:52:54 +0200
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children 0ec06ca3fc36
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1159:1ad7da049b50 1160:76e3bb7836cf
1 classdef RungekuttaExteriorRvMg < time.Timestepper
2 properties
3 F % RHS of the ODE
4 k % Time step
5 t % Time point
6 v % Solution vector
7 n % Time level
8 rkScheme % The particular RK scheme used for time integration
9 RV % Residual Viscosity operator
10 DvDt % Function for computing the time deriative used for the RV evaluation
11 v_unstable
12 viscosity
13 end
14 methods
15
16 function obj = RungekuttaExteriorRvMg(F, k, t0, v0, RV, DvDt, order)
17 obj.F = F;
18 obj.k = k;
19 obj.t = t0;
20 obj.v = v0;
21 obj.n = 0;
22
23 if (order == 4) % Use specialized RK4 scheme
24 obj.rkScheme = @time.rk.rungekutta_4;
25 else
26 % Extract the coefficients for the specified order
27 % used for the RK updates from the Butcher tableua.
28 [s,a,b,c] = time.rk.butcherTableau(order);
29 coeffs = struct('s',s,'a',a,'b',b,'c',c);
30 obj.rkScheme = @(v,t,dt,F) time.rk.rungekutta(v, t , dt, F, coeffs);
31 end
32
33 obj.RV = RV;
34 obj.DvDt = DvDt;
35 obj.v_unstable = 0*v0
36 obj.viscosity = 0*v0
37 end
38
39 function [v, t] = getV(obj)
40 v = obj.v;
41 t = obj.t;
42 end
43
44 function state = getState(obj)
45 dvdt = obj.DvDt(obj.v_unstable);
46 [viscosity, Df, firstOrderViscosity, residualViscosity] = obj.RV.evaluate(obj.v, dvdt);
47 state = struct('v', obj.v, 'dvdt', dvdt, 'Df', Df, 'viscosity', viscosity, 'residualViscosity', residualViscosity, 'firstOrderViscosity', firstOrderViscosity, 't', obj.t);
48 end
49
50 % Advances the solution vector one time step using the Runge-Kutta method given by
51 % obj.coeffs, using a fixed residual viscosity for the Runge-Kutta substeps
52 function obj = step(obj)
53 % Fix the viscosity of the RHS function F
54 m = length(obj.viscosity);
55 F_stable = @(v,t) obj.F(v,t,spdiags(obj.viscosity,0,m,m));
56 F_unstable = @(v,t) obj.F(v,t,spdiags(0*obj.viscosity,0,m,m));
57 obj.v = obj.rkScheme(obj.v, obj.t, obj.k, F_stable);
58 obj.v_unstable = obj.rkScheme(obj.v, obj.t, obj.k, F_unstable);
59 obj.viscosity = obj.RV.evaluateViscosity(obj.v, obj.DvDt(obj.v_unstable));
60 obj.t = obj.t + obj.k;
61 obj.n = obj.n + 1;
62 end
63 end
64 end