Initial commit

2016-02-03 18:52:05 +00:00
commit d40505e161
507 changed files with 91383 additions and 0 deletions
@@ -0,0 +1,28 @@
+      SUBROUTINE rk4(y,dydx,n,x,h,yout,derivs)
+      INTEGER n,NMAX
+      REAL h,x,dydx(n),y(n),yout(n)
+      EXTERNAL derivs
+      PARAMETER (NMAX=50)
+      INTEGER i
+      REAL h6,hh,xh,dym(NMAX),dyt(NMAX),yt(NMAX)
+      hh=h*0.5
+      h6=h/6.
+      xh=x+hh
+      do 11 i=1,n
+        yt(i)=y(i)+hh*dydx(i)
+11    continue
+      call derivs(xh,yt,dyt)
+      do 12 i=1,n
+        yt(i)=y(i)+hh*dyt(i)
+12    continue
+      call derivs(xh,yt,dym)
+      do 13 i=1,n
+        yt(i)=y(i)+h*dym(i)
+        dym(i)=dyt(i)+dym(i)
+13    continue
+      call derivs(x+h,yt,dyt)
+      do 14 i=1,n
+        yout(i)=y(i)+h6*(dydx(i)+dyt(i)+2.*dym(i))
+14    continue
+      return
+      END