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arxiv: 2604.13413 · v1 · submitted 2026-04-15 · 💻 cs.LG

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Dataset-Level Metrics Attenuate Non-Determinism: A Fine-Grained Non-Determinism Evaluation in Diffusion Language Models

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Pith reviewed 2026-05-10 13:28 UTC · model grok-4.3

classification 💻 cs.LG
keywords diffusion language modelsnon-determinism evaluationdataset-level metricssample-level analysisFactor Variance Attributioncode generationquestion answering
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The pith

Dataset-level metrics systematically mask non-determinism in diffusion language models by averaging across samples and runs.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that standard dataset-level metrics for diffusion language models hide substantial variability because they combine prediction quality from many individual samples and separate runs into single aggregate scores. This averaging produces the appearance of stability even when the same model and input produce different outputs under small changes to guidance scale, diffusion steps, batch size, hardware, or numerical precision. Shifting attention to direct sample-level prediction differences uncovers that non-determinism is both widespread and patterned, appearing far more strongly in code-generation tasks than in question answering. The authors introduce Factor Variance Attribution to measure how much of the observed variation can be traced to each factor setting.

Core claim

Dataset-level metrics attenuate non-determinism in diffusion language models by aggregating sample-level prediction quality across different runs. As a result, configurations with similar aggregate performance can exhibit substantially different behaviors on individual inputs. Fine-grained analysis across model and system factors reveals that non-determinism is pervasive and structured, with code generation showing markedly higher sensitivity than question answering.

What carries the argument

Factor Variance Attribution (FVA), a cross-factor metric that decomposes observed sample-level non-determinism into portions attributable to each evaluation factor such as guidance scale or hardware precision.

If this is right

  • Configurations that look equivalent under dataset averages can differ substantially on specific inputs and error types.
  • Non-determinism strength depends on task type, reaching higher levels in code generation than in question answering.
  • Both model factors such as diffusion steps and system factors such as numerical precision contribute measurable variance.
  • Reliable assessment of diffusion language models requires factor-aware, sample-level metrics in addition to aggregates.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Reporting only averages may lead practitioners to underestimate deployment risk when outputs must remain consistent on single queries.
  • The same sample-level decomposition could be applied to other generative architectures to locate common sources of run-to-run drift.
  • Developers could add variance-aware benchmarks that require models to keep individual-sample disagreement below a stated threshold.

Load-bearing premise

Observed differences in sample-level predictions across runs and factor settings reflect the models' inherent non-determinism rather than unaccounted implementation details or limited Monte Carlo sampling.

What would settle it

Reproduce the sample-level comparisons while holding every implementation detail fixed, using identical hardware, and drawing thousands of Monte Carlo samples per input; if prediction differences across runs then disappear or fall within expected statistical noise, the claim of pervasive structured non-determinism would be falsified.

Figures

Figures reproduced from arXiv: 2604.13413 by Huiyuan Chen, Jing Li, Kaiyu Tang, Tianyi Li, Xiaoge Zhang, Xiao Li, Zhengyu Fang, Zhimeng Jiang.

Figure 1
Figure 1. Figure 1: Sample-level prediction flip rates across inference-time configurations. Each panel varies one inference factor while holding all other factors fixed: (a) batch size, (b) classifier-free guidance (CFG) scale, and (c) number of Monte Carlo (MC) samples. For a given sample s, the prediction flip rate is defined as 1 − maxa|{c ∈ C : ˆys,c = a}|/|C|, where yˆs,c denotes the predicted label for sample s under c… view at source ↗
Figure 2
Figure 2. Figure 2: This hierarchy underlies our sample-aware and factor-aware evaluation paradigm and is formally instantiated by the definitions in Section 3.2. differ (Ribeiro et al., 2020). The consistency of this phe￾nomenon across factors suggests that such non-determinism is not an isolated artifact, but a recurring property of diffu￾sion language model evaluation. Towards Factor-Aware and Sample-Aware Evaluation. The … view at source ↗
Figure 3
Figure 3. Figure 3: Within-factor variability across datasets and backbones. The figure reports the standard deviation (Std) of evaluation scores across different settings within each factor, aggregated by dataset. Larger Std indicates stronger sensitivity to specific settings of the same factor, reflecting pronounced setting-level non-determinism. Results are shown for both LLaDA and LLaDA-1.5 on question answering and code … view at source ↗
Figure 4
Figure 4. Figure 4: Uncertainty of factor-level effects across datasets and backbones. The figure reports the standard error (SE) of the mean evaluation score for each factor, aggregated across its settings. SE reflects the reliability of the estimated factor-level effect and complements within-factor variability by characterizing uncertainty at the factor level. Together with FVA, this analysis clarifies how evaluation non-d… view at source ↗
read the original abstract

Diffusion language models (DLMs) have emerged as a promising paradigm for large language models (LLMs), yet the non-deterministic behavior of DLMs remains poorly understood. The existing non-determinism evaluations for LLMs predominantly rely on dataset-level metrics under fixed inference configurations, providing limited insight into how model behavior varies across runs and evaluation conditions. In this work, we show that dataset-level metrics systematically attenuate non-determinism in diffusion language models by aggregating sample-level prediction quality across different runs. As a result, configurations with similar aggregate performance can exhibit substantially different behaviors on individual inputs, leaving fine-grained instability and distinct error patterns uncharacterized. To address this limitation, we conduct a fine-grained evaluation of non-determinism based on sample-level prediction differences across a range of model-related factors-including guidance scale, diffusion steps, and Monte Carlo sampling-as well as system-related factors such as batch size, hardware, and numerical precision. Our analysis reveals that non-determinism in DLMs is pervasive and structured, with code generation exhibiting markedly higher sensitivity to factor-level choices than question answering. To attribute sources of non-determinism evaluation, we introduce Factor Variance Attribution (FVA), a cross-factor analysis metric that decomposes observed non-determinism into variance attributable to different evaluation factor settings. Our findings highlight the need for fine-grained, factor-aware evaluation to enable reliable non-determinism assessment of diffusion language models.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 1 minor

Summary. The paper claims that dataset-level metrics attenuate non-determinism in diffusion language models (DLMs) by averaging sample-level prediction quality across runs, such that configurations with similar aggregates can hide substantially different per-input behaviors. It conducts a fine-grained analysis of non-determinism across model factors (guidance scale, diffusion steps, Monte Carlo sampling) and system factors (batch size, hardware, numerical precision), reports that non-determinism is pervasive and task-dependent (higher in code generation than QA), and introduces Factor Variance Attribution (FVA) as a cross-factor decomposition metric to attribute observed variance to specific evaluation settings.

Significance. If the empirical findings hold, the work identifies a systematic limitation in how non-determinism is currently assessed for an emerging LLM paradigm, motivating factor-aware and sample-level evaluation protocols. The FVA metric offers a concrete tool for variance decomposition that could be adopted more broadly, and the task-specific sensitivity results provide actionable guidance for inference configuration choices in DLMs.

major comments (1)
  1. [Abstract and §3] Abstract and §3 (Evaluation Methodology): The central attenuation claim requires that observed sample-level prediction differences across runs and factor settings primarily reflect inherent model non-determinism rather than unaccounted implementation artifacts. The manuscript states that system factors are evaluated, yet provides no explicit controls or reporting for diffusion-specific sources of nondeterminism such as per-denoising-step RNG state, floating-point reduction order in attention, or library nondeterminism flags; without these, the base measurements feeding FVA may be contaminated, undermining the attribution and the claim that dataset-level metrics systematically attenuate true non-determinism.
minor comments (1)
  1. [Abstract] The abstract refers to 'Monte Carlo sampling' as a factor but does not specify the number of samples drawn per configuration or the exact variance estimator used; this detail should be added in the methods for reproducibility.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive feedback and for identifying a key methodological gap. We agree that stronger documentation of controls is needed to support the central claims. We address the major comment below and will revise the manuscript accordingly.

read point-by-point responses
  1. Referee: [Abstract and §3] Abstract and §3 (Evaluation Methodology): The central attenuation claim requires that observed sample-level prediction differences across runs and factor settings primarily reflect inherent model non-determinism rather than unaccounted implementation artifacts. The manuscript states that system factors are evaluated, yet provides no explicit controls or reporting for diffusion-specific sources of nondeterminism such as per-denoising-step RNG state, floating-point reduction order in attention, or library nondeterminism flags; without these, the base measurements feeding FVA may be contaminated, undermining the attribution and the claim that dataset-level metrics systematically attenuate true non-determinism.

    Authors: We acknowledge that the manuscript provides insufficient explicit reporting on diffusion-specific nondeterminism sources. Although system factors (batch size, hardware, numerical precision) were varied and reported at a high level, we did not document per-denoising-step RNG state handling, attention reduction orders, or library flags such as torch.use_deterministic_algorithms. In the revision we will expand §3 (Evaluation Methodology) with: (i) the precise RNG seeding protocol applied at each diffusion step, (ii) the nondeterminism flags and environment settings used, and (iii) any steps taken to stabilize floating-point reduction order. These additions will allow readers to assess whether the sample-level differences primarily reflect the intended model and system factors. We maintain that the observed attenuation of non-determinism by dataset-level metrics remains valid across the tested configurations, but we agree that the requested documentation is necessary to fully substantiate the FVA attribution. revision: yes

Circularity Check

0 steps flagged

No circularity: empirical definitions and variance decomposition remain independent of inputs

full rationale

The paper is an empirical evaluation that defines non-determinism directly from observed sample-level prediction differences across runs and factor settings, then reports the attenuation effect of dataset-level aggregation as a measured outcome rather than a derived equation. The introduced FVA metric decomposes observed variance into factor contributions via standard cross-factor analysis without reducing to fitted parameters or prior self-citations. No load-bearing steps invoke self-definitional loops, uniqueness theorems from the same authors, or ansatzes smuggled via citation; the central claims rest on experimental measurements that can be independently replicated or falsified.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The central claim rests on the domain assumption that sample-level prediction differences across runs constitute measurable non-determinism and that the chosen factors are the relevant sources of variance.

axioms (1)
  • domain assumption Non-determinism in DLMs can be quantified by differences in per-sample predictions across repeated runs under varied factor settings
    Invoked when the paper defines fine-grained evaluation and attributes variance to factors.
invented entities (1)
  • Factor Variance Attribution (FVA) no independent evidence
    purpose: Decompose observed non-determinism into contributions from individual evaluation factors
    New metric introduced to attribute sources of instability

pith-pipeline@v0.9.0 · 5585 in / 1260 out tokens · 50463 ms · 2026-05-10T13:28:36.942538+00:00 · methodology

discussion (0)

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