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Enhancement - Fix preprocessing crash when num_workers=0 in Megatron GPT3 dataset generation #800

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Enhancement - Fix preprocessing crash when num_workers=0 in Megatron GPT3 dataset generation #800

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5 changes: 4 additions & 1 deletion superbench/benchmarks/model_benchmarks/megatron_gpt3.py
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Original file line number Diff line number Diff line change
Expand Up @@ -651,13 +651,16 @@ def _generate_dataset(self):
if self._args.dataset_url:
self._raw_data_path = str(Path(self._args.data_home) / 'data.json')
download_file(self._args.dataset_url, self._raw_data_path)

command = (
'python3 '
f'{os.path.join(self._args.code_base, "tools/preprocess_data.py")} '
f'--input {self._raw_data_path} '
f'--tokenizer-type {self._args.tokenizer_type} '
f'--output-prefix {os.path.join(self._args.data_home, "dataset")} '
f'--workers {str(self._args.num_workers)} '
# num_workers=0 is valid for DataLoader (main process loads data),
# but preprocess_data.py requires workers>=1 for multiprocessing.Pool.
f'--workers {max(1, self._args.num_workers)} '
Comment on lines +661 to +663
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Copilot AI Apr 1, 2026

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The new max(1, self._args.num_workers) clamp is a regression-critical behavior change (fixing the multiprocessing.Pool(0) crash), but there’s no unit test asserting that --workers passed to preprocess_data.py is at least 1 when --num_workers=0. Since this benchmark already has tests, consider adding a test that exercises _generate_dataset() with num_workers=0 and asserts the constructed preprocess command uses --workers 1.

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f'--vocab-file {self._vocab_path} '
Comment on lines 659 to 664
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Copilot AI Apr 1, 2026

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--output-prefix is hardcoded to ${data_home}/dataset, but the rest of the method uses self._args.data_prefix (and exposes it as a CLI arg). If --data_prefix is customized and the dataset needs to be generated (no existing .bin/.idx), preprocessing will generate dataset_text_document.* while the code checks for {data_prefix}.*, leading to a false failure. Consider deriving --output-prefix from data_prefix (e.g., strip a _text_document suffix when present) so generation and subsequent checks are consistent.

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f'--merge-file {self._merges_path}'
)
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