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annotate +rv/+time/RungekuttaRvMultiGrid.m @ 1169:d02e5b8a0b24 feature/rv

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Rename RungekuttaRV time steppers. Add RungekuttaRVMultiStage time stepper
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Fri, 28 Jun 2019 13:13:17 +0200
parents +rv/+time/RungekuttaExteriorRvMg.m@745ae0d134c9
children b96b1245a77d
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1 classdef RungekuttaRvMultiGrid < time.Timestepper
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2 properties
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3 F % RHS of the ODE
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4 F_coarse % RHS of the unstabalized ODE
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5 k % Time step
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6 t % Time point
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7 v % Solution vector
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8 n % Time level
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9 rkScheme % The particular RK scheme used for time integration
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10 RV % Residual Viscosity operator
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11 DvDt % Function for computing the time deriative used for the RV evaluation
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12 v_unstable
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13 viscosity
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14 end
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15 methods
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16
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17 function obj = RungekuttaRvMultiGrid(F, F_coarse, k, t0, v0, RV, DvDt, order)
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18 obj.F = F;
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19 obj.F_coarse = F_coarse;
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20 obj.k = k;
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21 obj.t = t0;
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22 obj.v = v0;
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23 obj.n = 0;
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24
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25 if (order == 4) % Use specialized RK4 scheme
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26 obj.rkScheme = @time.rk.rungekutta_4;
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27 else
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28 % Extract the coefficients for the specified order
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29 % used for the RK updates from the Butcher tableua.
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30 [s,a,b,c] = time.rk.butcherTableau(order);
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31 coeffs = struct('s',s,'a',a,'b',b,'c',c);
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32 obj.rkScheme = @(v,t,dt,F) time.rk.rungekutta(v, t , dt, F, coeffs);
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33 end
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34
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35 obj.RV = RV;
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36 obj.DvDt = DvDt;
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37 obj.v_unstable = 0*v0;
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38 obj.viscosity = 0*v0;
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39 end
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40
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41 function [v, t] = getV(obj)
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42 v = obj.v;
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43 t = obj.t;
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44 end
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45
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46 function state = getState(obj)
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47 dvdt = obj.DvDt(obj.v_unstable);
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48 [viscosity, Df, firstOrderViscosity, residualViscosity] = obj.RV.evaluate(obj.v, dvdt);
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49 state = struct('v', obj.v, 'dvdt', dvdt, 'Df', Df, 'viscosity', obj.viscosity, 'residualViscosity', residualViscosity, 'firstOrderViscosity', firstOrderViscosity, 't', obj.t);
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50 end
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51
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52 % Advances the solution vector one time step using the Runge-Kutta method given by
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53 % obj.coeffs, using a fixed residual viscosity for the Runge-Kutta substeps
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54 function obj = step(obj)
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55 m = length(obj.viscosity);
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56 obj.v_unstable = obj.rkScheme(obj.v, obj.t, obj.k, obj.F_coarse);
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57 obj.viscosity = obj.RV.evaluateViscosity(obj.v, obj.DvDt(obj.v_unstable));
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58 % Fix the viscosity of the stabilized RHS
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59 F_stable = @(v,t) obj.F(v,t,spdiags(obj.viscosity,0,m,m));
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60 obj.v = obj.rkScheme(obj.v, obj.t, obj.k, F_stable);
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61 obj.t = obj.t + obj.k;
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62 obj.n = obj.n + 1;
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63 end
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64 end
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65 end