Do Post-Training Algorithms Actually Differ? A Controlled Study Across Model Scales Uncovers Scale-Dependent Ranking Inversions

📰 ArXiv cs.AI

A controlled study compares 51 post-training algorithms across 4 model scales, revealing scale-dependent ranking inversions

advanced Published 23 Mar 2026
Action Steps
  1. Implement a unified framework to compare post-training algorithms
  2. Evaluate algorithms across multiple model scales and domains
  3. Analyze results to identify scale-dependent ranking inversions
  4. Select the most suitable algorithm based on the specific model scale and evaluation domain
Who Needs to Know This

AI engineers and ML researchers benefit from this study as it provides a comprehensive comparison of post-training algorithms, helping them make informed decisions for their models

Key Insight

💡 Post-training algorithm performance can vary significantly depending on the model scale, and a unified framework is necessary for fair comparisons

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🤖 New study compares 51 post-training algorithms across 4 model scales, revealing surprising scale-dependent ranking inversions!

Key Takeaways

A controlled study compares 51 post-training algorithms across 4 model scales, revealing scale-dependent ranking inversions

Full Article

Title: Do Post-Training Algorithms Actually Differ? A Controlled Study Across Model Scales Uncovers Scale-Dependent Ranking Inversions

Abstract:
arXiv:2603.19335v1 Announce Type: cross Abstract: Post-training alignment has produced dozens of competing algorithms -- DPO, SimPO, KTO, GRPO, and others -- yet practitioners lack controlled comparisons to guide algorithm selection. We present OXRL, a unified framework implementing 51 post-training algorithms with identical infrastructure, enabling the first large-scale apples-to-apples evaluation. Our study spans 8 algorithms across 4 model scales (0.5B--7B), 3 evaluation domains, and a 20-var
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