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comparison +time/+rk/General.m @ 993:44e7e497c3b7 feature/timesteppers

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Make time.rk.General accept a butcher tableau instead of a string to choose method. String variant implemented as a static method
author Jonatan Werpers <jonatan@werpers.com>
date Wed, 09 Jan 2019 11:14:16 +0100
parents bbd165cc585c
children 10c5eda235b7
comparison
equal deleted inserted replaced
992:bbd165cc585c 993:44e7e497c3b7
11 K % All stage rates in most recent time step 11 K % All stage rates in most recent time step
12 end 12 end
13 13
14 14
15 methods 15 methods
16 % Timesteps v_t = F(v,t), using the specified RK method from t = t0 with 16 % Timesteps v_t = F(v,t), using the specified ButcherTableau
17 % timestep dt and initial conditions v = v0 17 % from t = t0 with timestep dt and initial conditions v(0) = v0
18 function obj = General(F, dt, t0, v0, method, discreteData) 18 function obj = General(F, dt, t0, v0, bt, discreteData)
19 default_arg('method',"rk4"); 19 assertType(bt, 'time.rk.ButcherTableau')
20 default_arg('discreteData', []); 20 default_arg('discreteData', []);
21 obj.F = F; 21 obj.F = F;
22 obj.dt = dt; 22 obj.dt = dt;
23 obj.t = t0; 23 obj.t = t0;
24 obj.v = v0; 24 obj.v = v0;
25 obj.n = 0; 25 obj.n = 0;
26 26
27 % Extract the coefficients for the specified method 27 assert(bt.isExplicit())
28 % used for the RK updates from the Butcher tableua. 28 obj.coeffs = struct('s',bt.nStages,'a',bt.a(:,1:end-1),'b',bt.b,'c',bt.c);
29 [s,a,b,c] = time.rk.butcherTableauFromStr(method);
30 obj.coeffs = struct('s',s,'a',a,'b',b,'c',c);
31 29
32 if isempty(discreteData) 30 if isempty(discreteData)
33 obj.scheme = @(v,t,n) time.rk.rungekutta(v, t, dt, F, obj.coeffs); 31 obj.scheme = @(v,t,n) time.rk.rungekutta(v, t, dt, F, obj.coeffs);
34 else 32 else
35 obj.scheme = @(v,t,n) time.rk.rungekuttaDiscreteData(v, t, dt, F, obj.coeffs, discreteData, n); 33 obj.scheme = @(v,t,n) time.rk.rungekuttaDiscreteData(v, t, dt, F, obj.coeffs, discreteData, n);
76 N = round( (tEnd-t0)/obj.dt ); 74 N = round( (tEnd-t0)/obj.dt );
77 b = obj.coeffs.b; 75 b = obj.coeffs.b;
78 weights = repmat(b', N, 1); 76 weights = repmat(b', N, 1);
79 end 77 end
80 end 78 end
79
80 methods(Static)
81 % TBD: Function name
82 function ts = methodFromStr(F, dt, t0, v0, methodStr, discreteData)
83 default_arg('discreteData', []);
84
85 try
86 bt = time.rk.ButcherTableau.(method);
87 catch
88 error('Runge-Kutta method ''%s'' is not implemented', methodStr)
89 end
90
91 ts = time.rk.General(F, dt, t0, v0, bt, discreteData);
92 end
93 end
81 end 94 end