Issue fine_tuning_select

[luimaren]

The mace.cli.fine_tuning_select command fails when attempting to write the selected replay configurations, raising an exception that indicates the output filename is not compatible with the ExtXYZ format, even though the filename is valid and ASE correctly recognizes it as an ExtXYZ file.

I reproduced the exact same error using different foundation models (mace-mpa-0-medium.model).

I discard any issue with my fine-tuning dataset, since I created a new dataset by copying a few configurations directly from the replay dataset itself, so both input files have exactly the same format and structure. Even in this case, fine_tuning_select reports exactly the same error.

Here, I simplified the replay selection as much as possible by requesting only 100 replay configurations with random sampling (--num_samples 100 and --subselect random), avoiding more complex selection methods such as FPS and --num_samples 10000. Also, in that cases failed.

Thanks in advance for any help.

Environment

• OS: Windows 11
• Python: Conda environment
• MACE: 0.3.16
• ASE: 3.29.0

Command

python -m mace.cli.fine_tuning_select
--configs_pt replay-data-mh-1-omat-pbe.xyz
--configs_ft dataset_BGDY.xyz
--num_samples 100
--subselect random
--model mace-mh-1.model
--output selected_configs.xyz
--head_pt oc20_usemppbe
--head_ft Default
--weight_pt 1.0
--weight_ft 10.0

Output

C:\Users\luism\anaconda3\envs\mace_new\lib\site-packages\e3nn\o3_wigner.py:10: FutureWarning: You are using torch.load with weights_only=False (the current default value), which uses the default pickle module implicitly. It is possible to construct malicious pickle data which will execute arbitrary code during unpickling (See https://github.com/pytorch/pytorch/blob/main/SECURITY.md#untrusted-models for more details). In a future release, the default value for weights_only will be flipped to True. This limits the functions that could be executed during unpickling. Arbitrary objects will no longer be allowed to be loaded via this mode unless they are explicitly allowlisted by the user via torch.serialization.add_safe_globals. We recommend you start setting weights_only=True for any use case where you don't have full control of the loaded file. Please open an issue on GitHub for any issues related to this experimental feature.
_Jd, _W3j_flat, _W3j_indices = torch.load(os.path.join(os.path.dirname(file), 'constants.pt'))
2026-07-02 10:35:20 INFO Start: Parse command line arguments
2026-07-02 10:35:20 INFO Reading ./replay-data-mh-1-omat-pbe.xyz
2026-07-02 10:37:42 INFO Filtering configurations based on the finetuning set, filtering type: none, elements: ['B', 'C']
2026-07-02 10:37:42 INFO Subsample data
2026-07-02 10:37:42 INFO Subselecting 100 from filtered 372355 using random sampling
Traceback (most recent call last):
File "C:\Users\luism\anaconda3\envs\mace_new\lib\runpy.py", line 196, in _run_module_as_main
return _run_code(code, main_globals, None,
File "C:\Users\luism\anaconda3\envs\mace_new\lib\runpy.py", line 86, in _run_code
exec(code, run_globals)
File "C:\Users\luism\anaconda3\envs\mace_new\lib\site-packages\mace\cli\fine_tuning_select.py", line 575, in
main()
File "C:\Users\luism\anaconda3\envs\mace_new\lib\site-packages\mace\cli\fine_tuning_select.py", line 571, in main
select_samples(SelectionSettings(**vars(args)))
File "C:\Users\luism\anaconda3\envs\mace_new\lib\site-packages\mace\cli\fine_tuning_select.py", line 528, in select_samples
raise ValueError(
ValueError: filename './selected_configs.xyz' does no have suffix compatible with extxyz format