Entropy discrepancy during MCMC after copying state with new state_args (pclabel change)

I want to copy a state, but change the state_args (in my case changing the PropertyMap which specifies the pclabel).

After copying, the MCMC sometimes raises an Entropy error (code must be run a few times to observe the issue).

Minimal example (files here):

import graph_tool.all as gt
import pickle
from graph_tool import inference
inference.set_test(True)

# Loaded state has strict pclabel - Each question in its own group
with open('example_state.pickle', 'rb') as handle:
    state = pickle.load(handle)

# NEW STATE ARGS. Allow question groups to be merged
new_state_args = state.state_args.copy()
new_state_args['clabel'] = state.g.vp['kind'].copy()
new_state_args['pclabel'] = state.g.vp['kind'].copy()

# Copying state with new state_args causes entropy discrepancy
s = state.copy(state_args=new_state_args)
for i in range(10):
    ret = s.multiflip_mcmc_sweep(beta=1, niter=10)

Note that I get two different, but related error messages across different runs.

Error message 1:

Traceback (most recent call last):
  File "/Users/falkenbergm/Documents/Projects/WVS_Analysis/other/minimal_example_folder/minimal_example_14/minimal_example_14.py", line 24, in <module>
    ret = s.multiflip_mcmc_sweep(beta=1, niter=10)
  File "/opt/anaconda3/envs/gt/lib/python3.13/site-packages/graph_tool/inference/base_states.py", line 85, in wrapper
    Sf = self.entropy(**entropy_args)
  File "/opt/anaconda3/envs/gt/lib/python3.13/site-packages/graph_tool/inference/base_states.py", line 58, in wrapper
    assert math.isclose(S, Salt, abs_tol=1e-8), \
           ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: entropy discrepancy after copying (172591 172592 -1.38629)

Error message 2:

Traceback (most recent call last):
  File "/Users/falkenbergm/Documents/Projects/WVS_Analysis/other/minimal_example_folder/minimal_example_14/minimal_example_14.py", line 19, in <module>
    ret = s.multiflip_mcmc_sweep(beta=1, niter=10)
  File "/opt/anaconda3/envs/gt/lib/python3.13/site-packages/graph_tool/inference/base_states.py", line 86, in wrapper
    assert math.isclose(dS, (Sf - Si), abs_tol=1e-8), \
           ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: inconsistent entropy delta -2003.88 (-1976.17): {}
  • Are you running the latest graph-tool version?: v2.98
  • Did you compile graph-tool manually?: No (conda version)
  • Your operating system: MacOS Tahoe 26.0.1
  • The Python version you are using: 3.13