Initial commit

2016-02-03 18:52:05 +00:00
commit d40505e161
507 changed files with 91383 additions and 0 deletions
@@ -0,0 +1,29 @@
+      SUBROUTINE mmid(y,dydx,nvar,xs,htot,nstep,yout,derivs)
+      INTEGER nstep,nvar,NMAX
+      REAL htot,xs,dydx(nvar),y(nvar),yout(nvar)
+      EXTERNAL derivs
+      PARAMETER (NMAX=50)
+      INTEGER i,n
+      REAL h,h2,swap,x,ym(NMAX),yn(NMAX)
+      h=htot/nstep
+      do 11 i=1,nvar
+        ym(i)=y(i)
+        yn(i)=y(i)+h*dydx(i)
+11    continue
+      x=xs+h
+      call derivs(x,yn,yout)
+      h2=2.*h
+      do 13 n=2,nstep
+        do 12 i=1,nvar
+          swap=ym(i)+h2*yout(i)
+          ym(i)=yn(i)
+          yn(i)=swap
+12      continue
+        x=x+h
+        call derivs(x,yn,yout)
+13    continue
+      do 14 i=1,nvar
+        yout(i)=0.5*(ym(i)+yn(i)+h*yout(i))
+14    continue
+      return
+      END