[Feature] Enhance dataset preprocessing memory management and fix hash failure

[xin3he]

Description

Reduced peak_ram from 9GB to 2.5GB for Qwen/Qwen3-0.6B

Details:

1. Subprocess Preprocessing:

   • Introduced a subprocess mode for dataset preprocessing.
     Since operations like datasets.map generate large temporary memory objects that gc.collect() cannot fully reclaim, running it in a forked subprocess ensures all memory is returned to the OS upon exit, preventing memory leaks during quantization.

2. add _make_map_fingerprint to fix below warning:

   Parameter 'function'=<function get_tokenizer_function.<locals>.default_tokenizer_function at 0x752e9b7b36a0> of the 
   transform datasets.arrow_dataset.Dataset._map_single couldn't be hashed properly, a random hash was used instead. Ma
   ke sure your transforms and parameters are serializable with pickle or dill for the dataset fingerprinting and cachi
   ng to work. If you reuse this transform, the caching mechanism will consider it to be different from the previous ca
   lls and recompute everything. This warning is only shown once. Subsequent hashing failures won't be shown.
   

3. Documentation:

   • Added docs/environments_CN.md as a Chinese translation of docs/environments.md, covering all environment variables including AR_DISABLE_DATASET_SUBPROCESS.
   • Added language toggle links between the English and Chinese documentation files.

Type of Change

• Bug fix
• New feature
• Documentation update
• Performance improvement
• Code refactoring
• Other (please specify):

Related Issues

Checklist Before Submitting

• My code has been tested locally.
• Documentation has been updated as needed.
• New or updated tests are included where applicable.

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[Copilot]

Pull request overview

This PR improves AutoRound’s calibration dataset preprocessing by reducing peak RAM via subprocess-based preprocessing and adding a persistent on-disk cache keyed by tokenizer/dataset parameters, with configuration exposed through environment variables.

Changes:

• Added subprocess preprocessing mode for calibration dataset generation with in-process fallback.
• Implemented a disk cache for preprocessed calibration datasets using a SHA-256–derived key and a completion marker.
• Integrated new environment variables into envs.py and documented them in docs/environments.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
docs/environments.md	Documents new dataset preprocessing/caching environment variables.
auto_round/envs.py	Adds unified env accessors for disabling subprocess mode and selecting cache directory.
auto_round/calib_dataset.py	Introduces subprocess-based preprocessing and persistent disk cache for calibration datasets.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

auto_round/calib_dataset.py:708

• The _get_dataset_impl docstring lists parameters like split and apply_chat_template that are not present in the function signature. This makes the internal API misleading and harder to maintain; please update the docstring to match the actual parameters and behavior.

def _get_dataset_impl(tokenizer, seqlen, dataset_name="NeelNanda/pile-10k", seed=42, nsamples=512):
    """Internal implementation: generate a dataset for calibration.

    Args:
        tokenizer (Tokenizer): The tokenizer to use for tokenization.
        seqlen (int): The exact sequence length. samples < seqlen will be dropped,
                      samples longer than seqlen will be truncated
        dataset_name (str, optional): The name of the dataset or datasets separated by commas.
                                     Defaults to "NeelNanda/pile-10k".
        split (str, optional): The data split to use. Defaults to None.
        seed (int, optional): The random seed for reproducibility. Defaults to 42.
        nsamples (int, optional): The total number of samples to include. Defaults to 512.
        apply_chat_template: Whether to apply chat template in tokenization.

[wenhuach21]

This PR should not target this release, as it introduces a new feature, right?

[xin3he]

/azp run Unit-Test-CUDA-AutoRound

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