arXiv AI

Structure Tax: How Structured Output affects LLMs Performance

The paper investigates the so‑called ‘structure tax’ that is often attributed to constraining large language model outputs to structured formats like JSON or XML. By evaluating various models, datasets, and schema designs, the authors find that the accuracy loss depends more on how the schema is organized than on the presence of structure itself. Specifically, reasoning‑first field ordering can match or surpass free‑form accuracy, whereas answer‑first ordering leads to significant drops, especially in smaller models. The study also shows that well‑designed schemas improve confidence calibration and the separability of correct versus incorrect representations in transformer layers.

arXiv AI
Sep 17

Schema-Key Wording as an Instruction Channel in Structured Generation under Constrained Decoding

The paper investigates how the wording of schema‑key tokens can serve as an implicit instruction channel in constrained decoding for structured generation. By treating structured generation as a multi‑channel instruction problem, the authors analyze when an instructional advantage is preserved after grammar projection and conduct experiments on GSM8K and Math500 across seven language models. Results show that changing only the schema‑key wording can significantly alter accuracy, with both positive and negative effects, and that prompt‑level and schema‑level instructions interact non‑additively.

By Yifan Le
arXiv Machine Learning
Sep 15

Specification Oracles

arXiv:2609.13415v1 Announce Type: new Abstract: Specifications face a basic tradeoff: leave details out, and important questions go unanswered; record every detail separately, and the specification b...

By Atticus Cull, Justin McCarthy
arXiv Machine Learning
Aug 31

Parser States Already Know: Structure-Conditioned KV Persistence for Structured Generation

The paper introduces PASK (Parser-Aware Structural KV Persistence), a method that leverages parser transitions to inform key‑value (KV) persistence decisions in structured generation tasks. By aligning KV compression with task‑level structured risk, PASK sets protection floors based on error sensitivity and allocates remaining KV capacity using attention‑output distortion, producing a lightweight, structure‑conditioned lookup policy. In experiments on Qwen3‑4B, PASK achieves a 17.39‑point accuracy gain over the best compressed baseline, while delivering up to 2.2× higher throughput, 3.3× lower TPOT, and 0.53× the peak GPU memory of full KV.

By Linze Wu, Xinrui Chen
arXiv AI
3d ago

Constrained Decoding: Harmful or Beneficial? Revisiting Its Impact on LLM Performance

The paper investigates whether constrained decoding harms or helps large language model (LLM) performance. It introduces a taxonomy of three constraint types—format, validity, and reasoning—and shows that suitable constraints can preserve or even improve performance by eliminating invalid paths. Experiments across multiple model families reveal that perceived performance drops are mainly due to non-equivalent prompting and output formats, while validity constraints boost reliability and reasoning constraints can enhance accuracy when they guide beneficial reasoning trajectories.

By Ngoc Trinh Hung Nguyen, Alonso Silva, Armen Aghasaryan, Mehwish Alam
arXiv Machine Learning
Jun 2

From Scaling to Structured Expressivity: Rethinking Transformers for CTR Prediction

arXiv:2511. 12081v2 Announce Type: replace-cross Abstract: Despite massive investments in scale, deep models for click-through rate (CTR) prediction often exhibit rapidly diminishing returns -- a stark contrast to the {predictable scaling laws} seen in large language models (LLMs).

By Bencheng Yan, Yuejie Lei, Zhiyuan Zeng, Zheye Deng, Di Wang, Kaiyi Lin, Pengjie Wang, Chuan Yu, Jian Xu, Bo Zheng
arXiv AI
Sep 10

LogicSkills: A Structured Benchmark for Formal Reasoning in Large Language Models

LogicSkills is a benchmark designed to isolate three core logical abilities in large language models: formal symbolization, countermodel construction, and validity assessment. The dataset draws items from the two-variable fragment of first‑order logic without identity, presented in both English and a Carrollian nonce‑word language, and all instances are solver‑verified with Z3. Results show that conventional instruction‑tuned LLMs excel at validity assessment but struggle with symbolization and countermodel construction, whereas recent reasoning‑tuned models perform well across all tasks, indicating a more systematic logical skill profile.

By Brian Rabern, Philipp Mondorf, Barbara Plank
arXiv AI
Aug 25

Revisiting the Effectiveness of LLM Pruning for Test-Time Scaling

The paper revisits the impact of pruning on large language models (LLMs) during test-time scaling (TTS). While prior work found that structured pruning degrades reasoning performance, this study shows that unstructured pruning—removing only specific redundant weights—can actually improve TTS performance on reasoning benchmarks for models s1.1-7B and Qwen3-8B, sometimes surpassing the full-weight models. The authors also examine how different layer-wise sparsity allocation strategies affect these outcomes.

By Ocean Monjur, Shahriar Kabir Nahin, Anshuman Chhabra