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comparison +rv/+time/RungekuttaExteriorRvBdf.m @ 1152:010bb2677230 feature/rv

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Clean up in +rv/+time. Make the time stepping more efficient by not storing unnessecary properties in the RK-RV time steppers
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Tue, 05 Mar 2019 10:53:34 +0100
parents 2ef20d00b386
children 3108963cc42c
comparison
equal deleted inserted replaced
1151:03ecf18d035f 1152:010bb2677230
13 DvDt % Function for computing the time deriative used for the RV evaluation 13 DvDt % Function for computing the time deriative used for the RV evaluation
14 lowerBdfOrder % Orders of the approximation of the time deriative, used for the RV evaluation. 14 lowerBdfOrder % Orders of the approximation of the time deriative, used for the RV evaluation.
15 % dictates which accuracy the boot-strapping should start from. 15 % dictates which accuracy the boot-strapping should start from.
16 upperBdfOrder % Orders of the approximation of the time deriative, used for the RV evaluation. 16 upperBdfOrder % Orders of the approximation of the time deriative, used for the RV evaluation.
17 % Dictates the order of accuracy used once the boot-strapping is complete. 17 % Dictates the order of accuracy used once the boot-strapping is complete.
18
19 % Convenience properties. Only for plotting
20 viscosity % Total viscosity
21 residualViscosity % Residual viscosity
22 firstOrderViscosity % first order viscosity
23 dvdt % Evaluated time derivative in residual
24 Df % Evaluated flux in residual
25 end 18 end
26 methods 19 methods
27 function obj = RungekuttaExteriorRvBdf(F, k, t0, v0, RV, rkOrder, bdfOrders) 20 function obj = RungekuttaExteriorRvBdf(F, k, t0, v0, RV, rkOrder, bdfOrders)
28 obj.F = F; 21 obj.F = F;
29 obj.k = k; 22 obj.k = k;
34 % used for the RK updates from the Butcher tableua. 27 % used for the RK updates from the Butcher tableua.
35 [s,a,b,c] = time.rk.butcherTableau(rkOrder); 28 [s,a,b,c] = time.rk.butcherTableau(rkOrder);
36 obj.coeffs = struct('s',s,'a',a,'b',b,'c',c); 29 obj.coeffs = struct('s',s,'a',a,'b',b,'c',c);
37 30
38 obj.RV = RV; 31 obj.RV = RV;
39 % TBD: Decide on if the initialization of the previous stages used by
40 % the BDF should be done here, or if it should be checked for each
41 % step taken.
42 % If it is moved here, then multiple branching stages can be removed in step()
43 % but this will effectively result in a plotted simulation starting from n = upperBdfOrder.
44 % In addition, the properties lowerBdfOrder and upperBdfOrder can be removed.
45 obj.lowerBdfOrder = bdfOrders.lowerBdfOrder; 32 obj.lowerBdfOrder = bdfOrders.lowerBdfOrder;
46 obj.upperBdfOrder = bdfOrders.upperBdfOrder; 33 obj.upperBdfOrder = bdfOrders.upperBdfOrder;
47 assert((obj.lowerBdfOrder >= 1) && (obj.upperBdfOrder <= 6)); 34 assert((obj.lowerBdfOrder >= 1) && (obj.upperBdfOrder <= 6));
48 obj.v_prev = []; 35 obj.v_prev = [];
49 obj.DvDt = rv.time.BdfDerivative(); 36 obj.DvDt = rv.time.BdfDerivative();
50 obj.viscosity = zeros(size(v0));
51 obj.firstOrderViscosity = zeros(size(v0));
52 obj.residualViscosity = zeros(size(v0));
53 obj.dvdt = zeros(size(v0));
54 obj.Df = zeros(size(v0));
55 end 37 end
56 38
57 function [v, t] = getV(obj) 39 function [v, t] = getV(obj)
58 v = obj.v; 40 v = obj.v;
59 t = obj.t; 41 t = obj.t;
60 end 42 end
61 43
62 function state = getState(obj) 44 function state = getState(obj)
63 state = struct('v', obj.v, 'dvdt', obj.dvdt, 'Df', obj.Df, 'viscosity', obj.viscosity, 'residualViscosity', obj.residualViscosity, 'firstOrderViscosity', obj.firstOrderViscosity, 't', obj.t); 45 if (size(obj.v_prev,2) >= obj.lowerBdfOrder)
46 dvdt = obj.DvDt.evaluate(obj.v, obj.v_prev, obj.k);
47 [viscosity, Df, firstOrderViscosity, residualViscosity] = obj.RV.evaluate(obj.v, dvdt);
48 else
49 viscosity = zeros(size(obj.v));
50 dvdt = zeros(size(obj.v));
51 Df = zeros(size(obj.v));
52 firstOrderViscosity = zeros(size(obj.v));
53 residualViscosity = zeros(size(obj.v));
54 end
55 state = struct('v', obj.v, 'dvdt', dvdt, 'Df', Df, 'viscosity', viscosity, 'residualViscosity', residualViscosity, 'firstOrderViscosity', firstOrderViscosity, 't', obj.t);
64 end 56 end
65 57
66 function obj = step(obj) 58 function obj = step(obj)
67 % Store current time level and update v_prev 59 nStoredStages = size(obj.v_prev,2);
68 numStoredStages = size(obj.v_prev,2); 60
69 if (numStoredStages < obj.upperBdfOrder) 61 %Calculate viscosity for the new time level
62 if (nStoredStages >= obj.lowerBdfOrder)
63 viscosity = obj.RV.evaluateViscosity(obj.v, obj.DvDt.evaluate(obj.v, obj.v_prev, obj.k));
64 else
65 viscosity = zeros(size(obj.v));
66 end
67
68 % Store current time level and update v_prev
69 if (nStoredStages < obj.upperBdfOrder)
70 obj.v_prev = [obj.v, obj.v_prev]; 70 obj.v_prev = [obj.v, obj.v_prev];
71 numStoredStages = numStoredStages+1;
72 else 71 else
73 obj.v_prev(:,2:end) = obj.v_prev(:,1:end-1); 72 obj.v_prev(:,2:end) = obj.v_prev(:,1:end-1);
74 obj.v_prev(:,1) = obj.v; 73 obj.v_prev(:,1) = obj.v;
75 end 74 end
76 75
77 % Fix the viscosity of the RHS function F 76 % Fix the viscosity of the RHS function F
78 F_visc = @(v,t) obj.F(v,t,obj.viscosity); 77 F_visc = @(v,t) obj.F(v, t, viscosity);
79 obj.v = time.rk.rungekutta(obj.v, obj.t, obj.k, F_visc, obj.coeffs); 78 obj.v = time.rk.rungekutta(obj.v, obj.t, obj.k, F_visc, obj.coeffs);
80 obj.t = obj.t + obj.k; 79 obj.t = obj.t + obj.k;
81 obj.n = obj.n + 1; 80 obj.n = obj.n + 1;
82
83 %Calculate dvdt and evaluate RV for the new time level
84 if ((numStoredStages >= obj.lowerBdfOrder) && (numStoredStages <= obj.upperBdfOrder))
85 obj.dvdt = obj.DvDt.evaluate(obj.v, obj.v_prev, obj.k);
86 [obj.viscosity, obj.Df, obj.firstOrderViscosity, obj.residualViscosity] = obj.RV.evaluate(obj.v,obj.dvdt);
87 end
88 end 81 end
89 end 82 end
90 end 83 end