Generally an error like this is due to a bug in yt. I don't know enough about the code you're using to provide useful advice, but perhaps we should be checking if `children` is `None` and doing something else. The "workaround" is likely to fix whatever bug you've run into.

On Fri, Sep 7, 2018 at 2:56 PM, Stephanie Tonnesen <stonnes@gmail.com> wrote:
Hi yt-users!

I have been fiddling some more with yt's clump finder and have another question.  I want to use density to find clumps, but want my maximum threshold value to be below the fiducial setting--instead of above the maximum possible density in the code I just want the finder to stop searching at, say 3.2e-24.  

The code was working but running out of memory until I set the max threshold, and I now get this error:

....lots of pleasant looking output messages....
Updating joins ... :   0%|          | 0/7 [00:00<?, ?it/s]
Updating joins ... : 100%|██████████| 7/7 [00:00<00:00, 48933.55it/s]
yt : [INFO     ] 2018-09-07 14:08:55,007 Investigating 2 children.
yt : [INFO     ] 2018-09-07 14:08:55,007 Finding clumps: min: 3.200000e-24, max: 3.200000e-24, step: 2.000000
yt : [INFO     ] 2018-09-07 14:08:55,041 Finding clumps: min: 3.200000e-24, max: 3.200000e-24, step: 2.000000
yt : [INFO     ] 2018-09-07 14:08:55,042 Eliminating invalid, childless clump with 2 cells.
yt : [INFO     ] 2018-09-07 14:08:55,042 1 of 2 children survived, linking its children to parent.
Traceback (most recent call last):
  File "yt_clump_fingert.py", line 59, in <module>
    find_clumps(master_clump, c_min, c_max, step)
  File "/mnt/home/stonnesen/yt-conda/yt/yt/analysis_modules/level_sets/clump_handling.py", line 444, in find_clumps
    find_clumps(child, min_val*d_clump, max_val, d_clump)
  File "/mnt/home/stonnesen/yt-conda/yt/yt/analysis_modules/level_sets/clump_handling.py", line 438, in find_clumps
    find_clumps(clump, min_val*d_clump, max_val, d_clump)
  File "/mnt/home/stonnesen/yt-conda/yt/yt/analysis_modules/level_sets/clump_handling.py", line 438, in find_clumps
    find_clumps(clump, min_val*d_clump, max_val, d_clump)
  File "/mnt/home/stonnesen/yt-conda/yt/yt/analysis_modules/level_sets/clump_handling.py", line 438, in find_clumps
    find_clumps(clump, min_val*d_clump, max_val, d_clump)
  File "/mnt/home/stonnesen/yt-conda/yt/yt/analysis_modules/level_sets/clump_handling.py", line 461, in find_clumps
    for child in clump.children:
TypeError: 'NoneType' object is not iterable

I tried to circumvent this error by changing my max to 2e-24 (not a multiple of 2 of 1e-25), and got the same error when the min was 3.2e-24 and the max was 2e-24 (!).  

Is there any way I can get around this error and have the clumpfinder stop looking once it has clump edges at my maximum density?

Thanks!
Stephanie
--
Dr. Stephanie Tonnesen
Associate Research Scientist
CCA, Flatiron Institute
New York, NY

stonnes@gmail.com

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