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comparison +time/+rk/rungekutta_6RV.m @ 846:c6fcee3fcf1b feature/burgers1d

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Add generalized RungeKutta and RungeKuttaRV class which extracts its coefficients from a butcher tableau, specified on the scheme.
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Thu, 20 Sep 2018 17:51:19 +0200
parents +time/+rk4/rungekutta_6RV.m@1e057b0f2fed
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845:1e057b0f2fed 846:c6fcee3fcf1b
1 % Takes one time step of size dt using the rungekutta method
2 % starting from v_0 and where the function F(v,t) gives the
3 % time derivatives.
4 function v = rungekutta_6RV(v, t , dt, F, RV)
5 s = 7;
6 k = zeros(length(v),s);
7 a = zeros(7,6);
8 c = [0, 4/7, 5/7, 6/7, (5-sqrt(5))/10, (5+sqrt(5))/10, 1];
9 b = [1/12, 0, 0, 0, 5/12, 5/12, 1/12];
10 a = [
11 0, 0, 0, 0, 0, 0;
12 4/7, 0, 0, 0, 0, 0;
13 115/112, -5/16, 0, 0, 0, 0;
14 589/630, 5/18, -16/45, 0, 0, 0;
15 229/1200 - 29/6000*sqrt(5), 119/240 - 187/1200*sqrt(5), -14/75 + 34/375*sqrt(5), -3/100*sqrt(5), 0, 0;
16 71/2400 - 587/12000*sqrt(5), 187/480 - 391/2400*sqrt(5), -38/75 + 26/375*sqrt(5), 27/80 - 3/400*sqrt(5), (1+sqrt(5))/4, 0;
17 -49/480 + 43/160*sqrt(5), -425/96 + 51/32*sqrt(5), 52/15 - 4/5*sqrt(5), -27/16 + 3/16*sqrt(5), 5/4 - 3/4*sqrt(5), 5/2 - 1/2*sqrt(5);
18 ];
19
20 k(:,1) = F(v,t,RV.getViscosity());
21
22 for i = 2:s
23 u = v;
24 for j = 1:i-1
25 u = u + dt*a(i,j)*k(:,j);
26 end
27 RV.update(u,v,c(i)*dt);
28 k(:,i) = F(u,t+c(i)*dt,RV.getViscosity());
29 end
30
31 u = v;
32 for i = 1:s
33 u = u + dt*b(i)*k(:,i);
34 end
35 RV.update(u,v,dt);
36 v = u;
37 end