Pass@k misses output diversity changes caused by model post-training

GRPO and rejection-sampling fine-tuning produced sharply different output distributions despite often similar pass@k scores.

Academic
Subham Rath · Raj Dandekar · Rajat Dandekar · Sreedath Panat

Accenture Strategy & Consulting · Vizuara AI Labs

Research Digest··3 min read
5B-Instruct checkpoint on grade-school mathematics.

5B-Instruct using Group Relative Policy Optimization (GRPO), a reinforcement-learning method based on verifier rewards, and rejection-sampling fine-tuning (RFT).

Why this paper

From Accenture Strategy & Consulting and Vizuara AI Labs

In one line

pass@k measures correct-answer probability but not output diversity, so it cannot detect post-training's effects on capability breadth.

What we could check

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  • ·No weights link found
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  • ✓Limitations stated by the authors
  • ✓Reports numbers on named benchmarks

Observed from the paper text and links we have. Absence here means we did not find it, not that it does not exist.

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Research Digest

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