Mercurial > repos > public > sbplib

changeset 916:d1c1615bd1a5 feature/timesteppers

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Add comment in butcherTableau about rk4-3/8 being irreducible.
author Martin Almquist <malmquist@stanford.edu>
date Mon, 26 Nov 2018 16:08:54 -0800
parents f5e14e5986b5
children 878652b22157
files +time/+rk/butcherTableau.m
diffstat 1 files changed, 7 insertions(+), 6 deletions(-) [+]
line wrap: on
line diff
--- a/+time/+rk/butcherTableau.m	Thu Nov 15 17:29:30 2018 -0800
+++ b/+time/+rk/butcherTableau.m	Mon Nov 26 16:08:54 2018 -0800
@@ -19,25 +19,26 @@
         % Standard RK4
         s = 4;
         a = zeros(s,s-1);
-        a(2,1) = 1/2; 
+        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
+        % 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(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 
+        % Runge-Kutta 6 from Alshina07
         s = 7;
         a = zeros(s,s-1);
-        a(2,1) = 4/7; 
+        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);
@@ -46,5 +47,5 @@
         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
-        error('That Runge-Kutta method is not implemented', method)    
+        error('That Runge-Kutta method is not implemented', method)
 end
\ No newline at end of file