Not able to read the Halo Finder output generated using HOP halo finder..

[chavan-shende]

What I am trying is to use yt HOP halo finder for identifying halos in a gadget/gizmo snapshot generated for DM cosmological Simulation. I was able to read the file, and then create the HaloCatalog, but when I am trying to load the HaloCatalog I am getting the error...

from yt.extensions.astro_analysis.halo_analysis import HaloCatalog

ds = yt.load("snapshot_012.0.hdf5")

hc = HaloCatalog(data_ds=ds, finder_method="hop")
hc.create()
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'''  The HaloCatalog was created successfully '''
yt : [INFO     ] 2025-01-09 22:03:43,323 Omega Lambda is 0.0, so we are turning off Cosmology.
yt : [INFO     ] 2025-01-09 22:03:43,324 Assuming length units are in kpc (physical)
yt : [INFO     ] 2025-01-09 22:03:43,354 Parameters: current_time              = 0.39999999999999997
yt : [INFO     ] 2025-01-09 22:03:43,355 Parameters: domain_dimensions         = [1 1 1]
yt : [INFO     ] 2025-01-09 22:03:43,355 Parameters: domain_left_edge          = [0. 0. 0.]
yt : [INFO     ] 2025-01-09 22:03:43,356 Parameters: domain_right_edge         = [100. 100. 100.]
yt : [INFO     ] 2025-01-09 22:03:43,357 Parameters: cosmological_simulation   = 0
yt : [INFO     ] 2025-01-09 22:03:43,398 Allocating for 2.097e+06 particles
Loading particle index: 100%|█████████████████████████| 9/9 [00:00<00:00, 816.61it/s]
yt : [INFO     ] 2025-01-09 22:03:43,944 Initializing HOP
Calling hop... 2097152 1.600e+02
yt : [INFO     ] 2025-01-09 22:04:08,221 Parsing outputs
Copying arrays for 2097152 particles
Building Tree...
Finding Densities...
Finding Densest Neighbors...
Grouping...
Merging Groups...
Writing Output...
All Done!
nSmooth = 65 kd->nActive = 2097152
Calling regroup...
No minimum group size specified.  Assuming 10 particles.
ngroups = 9545
yt : [INFO     ] 2025-01-09 22:04:24,939 Saving 1239 halos: halo_catalogs/snapshot_012/snapshot_012.0.h5.

But now when I am trying to read that HaloCatalog,

halo = yt.load("halo_catalogs/snapshot_012/snapshot_012.0.h5")
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# I am getting an error
AttributeError: 'YTHaloCatalogDataset' object has no attribute 'cosmology'

Please guide me if I am making any mistake...

Edit : I just tried on the dataset provided by yt

galaxy = yt.load_sample("IsolatedGalaxy")
hc = HaloCatalog(data_ds=galaxy, finder_method="hop", )
hc.create()

and I am getting the same "Attribute error" when I am trying to load the HaloCatalog file...

galaxy_halo = yt.load("halo_catalogs/galaxy0030/galaxy0030.0.h5")
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'YTHaloCatalogDataset' object has no attribute 'cosmology'

[welcome]

Hi, and welcome to yt! Thanks for opening your first issue. We have an issue template that helps us to gather relevant information to help diagnosing and fixing the issue.

[neutrinoceros]

This looks like a bug in yt_astro_analysis, in which case, this issue should be moved there. But I'll let @cphyc and @brittonsmith be the judges.