Mercurial > repos > public > sbplib
diff +time/+rk/butcherTableauFromStr.m @ 990:1066bb31bc95 feature/timesteppers
Create class for butcher tableau
author | Jonatan Werpers <jonatan@werpers.com> |
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date | Wed, 09 Jan 2019 09:09:15 +0100 |
parents | a32856fc2ad2 |
children |
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--- a/+time/+rk/butcherTableauFromStr.m Wed Jan 09 08:56:42 2019 +0100 +++ b/+time/+rk/butcherTableauFromStr.m Wed Jan 09 09:09:15 2019 +0100 @@ -6,46 +6,16 @@ % @return b - weights for summing stages % @return c - time step coefficents for intermediate stages function [s,a,b,c] = butcherTableauFromStr(method) -switch method - case "tvd-3" - % TVD (Total Variational Diminishing) - s = 3; - a = zeros(s,s-1); - a(2,1) = 1; - a(3,1) = 1/4; a(3,2) = 1/4; - b = [1/6, 1/6, 2/3]; - c = [0 1 1/2]; - case "rk4" - % Standard RK4 - s = 4; - a = zeros(s,s-1); - a(2,1) = 1/2; - a(3,1) = 0; a(3,2) = 1/2; - a(4,1) = 0; a(4,2) = 0; a(4,3) = 1; - b = [1/6 1/3 1/3 1/6]; - c = [0, 1/2, 1/2, 1]; - case "rk4-3/8" - % 3/8 RK4 (Kuttas method). Lower truncation error, more flops. - % Irreducible, unlike standard rk4. - s = 4; - a = zeros(s,s-1); - a(2,1) = 1/3; - a(3,1) = -1/3; a(3,2) = 1; - a(4,1) = 1; a(4,2) = -1; a(4,3) = 1; - b = [1/8 3/8 3/8 1/8]; - c = [0, 1/3, 2/3, 1]; - case "rk6" - % Runge-Kutta 6 from Alshina07 - s = 7; - a = zeros(s,s-1); - a(2,1) = 4/7; - a(3,1) = 115/112; a(3,2) = -5/16; - a(4,1) = 589/630; a(4,2) = 5/18; a(4,3) = -16/45; - a(5,1) = 229/1200 - 29/6000*sqrt(5); a(5,2) = 119/240 - 187/1200*sqrt(5); a(5,3) = -14/75 + 34/375*sqrt(5); a(5,4) = -3/100*sqrt(5); - a(6,1) = 71/2400 - 587/12000*sqrt(5); a(6,2) = 187/480 - 391/2400*sqrt(5); a(6,3) = -38/75 + 26/375*sqrt(5); a(6,4) = 27/80 - 3/400*sqrt(5); a(6,5) = (1+sqrt(5))/4; - a(7,1) = -49/480 + 43/160*sqrt(5); a(7,2) = -425/96 + 51/32*sqrt(5); a(7,3) = 52/15 - 4/5*sqrt(5); a(7,4) = -27/16 + 3/16*sqrt(5); a(7,5) = 5/4 - 3/4*sqrt(5); a(7,6) = 5/2 - 1/2*sqrt(5); - b = [1/12 0 0 0 5/12 5/12 1/12]; - c = [0, 4/7, 5/7, 6/7, (5-sqrt(5))/10, (5+sqrt(5))/10, 1]; - otherwise + try + bt = time.rk.ButcherTableau.(method); + catch error('Runge-Kutta method %s is not implemented', method) -end \ No newline at end of file + end + + assert(bt.isExplicit()); + + s = bt.nStages(); + a = bt.a(:,1:end-1); + b = bt.b; + c = bt.c; +end