arXiv Machine Learning

Beyond Distribution Matching: Selective Margin Preservation for Supervised Fine-Tuning

The paper introduces Selective Rank-Preserving Supervised Fine‑Tuning (SRP‑SFT), a method that applies a hinge‑based soft margin target to preserve selected local non‑target logit margins during teacher‑forced fine‑tuning. SRP‑SFT uses reference‑scaled lower bounds for pairs from the reference’s top‑K non‑target tokens, stopping once the bound is met. Experiments on Qwen3‑4B‑Base and UltraFeedback show that SRP‑SFT improves MATH‑500 and code‑generation scores compared to cross‑entropy and LP‑SFT baselines.

arXiv AI
Sep 30

PACT: Pairwise-Anchored Calibrated Tuning for Single-Token Typed Decisions

The paper introduces PACT, a tuning method for single-token typed-decision models that leverages contrastive pair data to add four training terms—difference-in-differences margin, permutation-consistency, evidence-necessity, and ordinal transport cost—without requiring new annotations. PACT achieves comparable accuracy to existing recipes while reducing position bias and ordinal error, and it improves robustness and stability across seeds. The authors provide code, data splits, and trained adapters for reproducibility.

By Yida Lin
arXiv Computation and Language
Aug 31

Nested Byte-Level Vocabularies Are Cheap to Deploy and Expensive to Share: A Pre-Registered Negative Result

The paper demonstrates that a byte‑level BPE tokenizer can be sliced to create multiple vocabulary sizes from a single trained model, preserving exact logits while reducing deployed weights by 66%. Experiments on 30 models show that while sliced models match the full model numerically, they underperform fixed‑cap specialists by a few percentage points in bits‑per‑byte. Multi‑cap training improves robustness to typographical noise, suggesting benefits from training across multiple granularities rather than from control tokens alone.

By Christos Koutsiaris
arXiv Computation and Language
Aug 28

TwinKV: A Composable Repair Pass for KV Cache Eviction via Pairwise Key Redundancy

TwinKV is a training‑free, attention‑free repair pass that identifies and swaps orphaned and redundant tokens in a KV cache, improving long‑context inference for small models. It works by detecting near‑duplicate keys and can be composed with existing eviction policies without altering their scoring rules. Experiments on Qwen3‑4B and Llama‑3.2‑1B across LongBench, LooGLE, RULER, and MMLU‑Pro show that TwinKV consistently improves performance for most configurations, especially at tighter compression ratios.

By Hong Chen, Yudong Zeng, Yongwei Huang, Zuhao Ouyang, Junyan Zhang, Xuming Hu
arXiv Machine Learning
Sep 22

ValueDiff: Value-Geometric KV Cache Eviction for Sink-Suppressed LLMs

ValueDiff introduces a value‑geometric KV cache eviction strategy for large language models that suppress attention sinks. It ranks tokens by the L2 deviation of their value vectors from the cache mean, a score that aligns with minimal‑disturbance eviction under a max‑entropy assumption. Across several benchmarks—RULER, LongBench, and MATH‑500—ValueDiff consistently retains a higher proportion of useful tokens than prior methods, especially under tight cache budgets.

By Junyoung Park, Jungwook Choi, Mingu Lee
arXiv Machine Learning
Aug 20

GEAR: Generative Expansion and Real Anchoring for Two-Stage Distillation of Tabular Foundation Models

GEAR is a two‑stage framework that distills tabular foundation models into lightweight MLP or tree‑based predictors for efficient CPU deployment. In the first stage, synthetic covariates are used as teacher‑query locations to train the student on soft TFM targets, expanding coverage beyond observed rows. The second stage re‑anchors the student to the target distribution using real labels and out‑of‑fold teacher predictions, preventing self‑labeling leakage and improving performance. Experiments on TALENT and TabArena show that GEAR‑distilled MLPs outperform supervised MLPs by up to 2.00 AUC points on binary tasks and 1.35 on multiclass tasks, and also outperform CatBoost, while dramatically reducing inference time and memory usage.

By Qi Qin, Jiajie Zhu, Dali Chen, Yuzhao Zhang, Jia-Xing Han, Yu Su, Peng Zhang, Ying Yan, Yifan Sun