fix: preference filter applies both length limits

[Chessing234]

Summary

• Preference filter used a nested ternary: if max_prompt_token_length was set, max_token_length was never checked.
• Match SFT: AND both checks independently.

GPU_TESTS=bypass

Test plan

• Unit: preference row with ok prompt length but oversize chosen/rejected is filtered when both limits set

Made with Cursor

[gemini-code-assist]

Code Review

This pull request updates the preference dataset filter in open_instruct/dataset_processor.py to apply both max_prompt_token_length and max_token_length constraints simultaneously, rather than treating them as mutually exclusive. A review comment suggests optimizing this filtering function by returning early (short-circuiting) as soon as any length check fails, which avoids unnecessary evaluations on large datasets.

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[gemini-code-assist]

We can optimize this filtering function by returning early (short-circuiting) as soon as any length check fails. This avoids unnecessary list length evaluations and boolean operations on subsequent checks, which can improve performance when processing large datasets.

Suggested change

	max_prompt_token_length_ok = True
	if self.config.max_prompt_token_length is not None:
	max_prompt_token_length_ok = len(row[INPUT_IDS_PROMPT_KEY]) <= self.config.max_prompt_token_length
	max_token_length_ok = True
	if self.config.max_token_length is not None:
	max_token_length_ok = (
	len(row[INPUT_IDS_CHOSEN_KEY]) <= self.config.max_token_length
	and len(row[INPUT_IDS_REJECTED_KEY]) <= self.config.max_token_length
	if self.config.max_token_length is not None
	else True
	)
	)
	return max_prompt_token_length_ok and max_token_length_ok
	if self.config.max_prompt_token_length is not None:
	if len(row[INPUT_IDS_PROMPT_KEY]) > self.config.max_prompt_token_length:
	return False
	if self.config.max_token_length is not None:
	if (
	len(row[INPUT_IDS_CHOSEN_KEY]) > self.config.max_token_length
	or len(row[INPUT_IDS_REJECTED_KEY]) > self.config.max_token_length
	):
	return False
	return True