[Yt-dev] clump finder stuff

[Matthew Turk]

Hi Stephen,

> In my dataset I've found that I need at least 52 for it to work in all cases. I did some statistics and the mean minimum multiplier required is 18 with a standard deviation of 9, so 52 is about 3 sigma out, so it's not that rare. I don't know how globally-applicable these statistics are; this is just one dataset.
>
> What I'm wondering is what we should do about this? Make the multiplier large enough to capture (N)sigma likelihood? Or wrap the call to construct_boundary_relationships in countour_finder.py in a while loop with a try/except that increases the multiplier with each failure?

So why does it need to be so high?  If you look at the sets of loops,
it should be fully-determined.

for i in range(nx):
  for j in range(ny):
    for offset_i in range(3):
      if i == 0 and oi == -1: continue without incrementing
      if i == ny - 1 and offset_i == 1: continue without incrementing
      for offset_j in range(3):
        if something: ti += 1
        if something_else: ti += 1

and then this gets repeated with nx&nz and ny&nz.

Maybe I missed the multiplication by two for the two possible
incrementations, so maybe it should be:

s = (ny*nx + nx*nz + nx*nz - 2) * 18

Either way, I think statistics here might be misguided.  It's a
fully-determined loop.  I just did the math wrong.

-Matt