;$Id: ploits.pro,v 1.2 2014/07/29 22:05:47 brandenb Exp $
;
;  Compute Loitsyansky invariant
;
nx=n_elements(var.x)
ny=n_elements(var.y)
nz=n_elements(var.z)
icount=0L
I=0.
;
;  shifts
;
stride=2
for n=0,nz-1,stride do begin
for m=0,ny-1,stride do begin
for l=0,nx-1,stride do begin
  dx=acos(cos(var.x(l)-var.x(0)))
  dy=acos(cos(var.y(m)-var.y(0)))
  dz=acos(cos(var.z(n)-var.z(0)))
  uprime=shift(var.uu,l,m,n,0)
  r2=dx^2+dy^2+dz^2
  I=I+mean(r2*dot(var.uu,uprime))
  icount=icount+1L
endfor
endfor
print,icount,I/icount
endfor
;
print,I/icount
u2=mean(dot2(var.uu))
t=var.t
cwd,run
fo='(f7.1,2e12.3,2x,a)'
print,t,I/icount,u2,run,fo=fo
openw,1,'tmp.dat'
printf,1,t,I/icount,u2,run,fo=fo
close,1
spawn,'cat tmp.dat >> ../idl/loits.dat'
END