Abstract:

While diffusion models have achieved remarkable performance in image generation, they often struggle with the imbalanced datasets frequently encountered in real-world applications, resulting in significant performance degradation on minority classes. In this paper, we identify model capacity allocation as a key and previously underexplored factor contributing to this issue, providing a perspective that is orthogonal to existing research. Our empirical experiments and theoretical analysis reveal that majority classes monopolize an unnecessarily large portion of the model's capacity, thereby restricting the representation of minority classes. To address this, we propose Capacity Manipulation (CM), which explicitly reserves model capacity for minority classes. Our approach leverages a low-rank decomposition of model parameters and introduces a capacity manipulation loss to allocate appropriate capacity for capturing minority knowledge, thus enhancing minority class representation. Extensive experiments demonstrate that CM consistently and significantly improves the robustness of diffusion models on imbalanced datasets, and when combined with existing methods, further boosts overall performance.

Disclaimer
This report is AI-GENERATED using Large Language Models and WisPaper (A scholar search engine). It analyzes academic papers' tasks and contributions against retrieved prior work. While this system identifies POTENTIAL overlaps and novel directions, ITS COVERAGE IS NOT EXHAUSTIVE AND JUDGMENTS ARE APPROXIMATE. These results are intended to assist human reviewers and SHOULD NOT be relied upon as a definitive verdict on novelty.
NOTE that some papers exist in multiple, slightly different versions (e.g., with different titles or URLs). The system may retrieve several versions of the same underlying work. The current automated pipeline does not reliably align or distinguish these cases, so human reviewers will need to disambiguate them manually.
If you have any questions, please contact: mingzhang23@m.fudan.edu.cn

Overview

Overall Novelty Assessment

The paper proposes a capacity allocation perspective for addressing class imbalance in diffusion models, introducing a Capacity Manipulation (CM) method that uses low-rank decomposition to reserve model parameters for minority classes. According to the taxonomy, this work resides in the 'Parameter-Level Capacity Manipulation' leaf under 'Model Capacity Allocation Approaches'. This leaf contains only two papers total, including the original work and one sibling paper, indicating a relatively sparse and emerging research direction within the broader field of imbalanced diffusion model training.

The taxonomy reveals two main branches for addressing class imbalance in diffusion models: capacity allocation approaches and data/sampling modifications. The original paper's branch focuses on internal model structure manipulation, while the neighboring 'Data and Sampling Strategy Modifications' branch addresses imbalance through noise sampling adjustments. The taxonomy explicitly distinguishes these approaches: capacity methods manipulate representational resources directly, whereas sampling methods recalibrate input distributions. This structural separation suggests the paper explores a complementary angle to existing work, though the overall taxonomy contains only two papers across these branches, indicating limited prior exploration of this problem space.

Among thirty candidates examined through semantic search, none were found to clearly refute any of the three main contributions. For the capacity allocation perspective, ten candidates were examined with zero refutable matches. Similarly, the CM method and theoretical analysis each had ten candidates examined, also with no clear prior work overlap. This suggests that within the limited search scope, the specific combination of low-rank decomposition for capacity reservation in imbalanced diffusion models appears relatively unexplored. However, the small scale of the search (thirty candidates total) and the sparse taxonomy (two papers) indicate this assessment is based on a narrow literature sample rather than exhaustive coverage.

Given the limited search scope and sparse taxonomy structure, the work appears to occupy a relatively novel position within the examined literature. The absence of refuting candidates across all contributions, combined with the small sibling set in the taxonomy leaf, suggests this capacity allocation framing may be underexplored. However, the analysis is constrained by examining only top-thirty semantic matches, leaving open the possibility of relevant work outside this scope, particularly in broader machine learning fairness or class imbalance literature beyond diffusion-specific contexts.

Taxonomy

Core-task Taxonomy Papers
2
3
Claimed Contributions
30
Contribution Candidate Papers Compared
0
Refutable Paper

Research Landscape Overview

Core task: Improving diffusion models on class-imbalanced datasets via capacity allocation. The field of diffusion model improvement under class imbalance organizes itself around two main branches. Model Capacity Allocation Approaches focus on how to distribute or manipulate the model's representational resources—such as parameters, attention mechanisms, or network layers—so that minority classes receive adequate capacity despite their scarcity in the training data. Data and Sampling Strategy Modifications, by contrast, address imbalance at the input level, adjusting how samples are drawn during training or how noise schedules are configured to ensure that underrepresented classes are not overshadowed by dominant ones. Together, these branches reflect complementary philosophies: one reshapes the model's internal structure, while the other reshapes the data stream it encounters. Within Model Capacity Allocation Approaches, a particularly active line of work explores parameter-level interventions that dynamically or statically assign different subsets of weights to different classes. Capacity Manipulation[0] exemplifies this direction by directly manipulating model parameters to allocate greater capacity to minority classes, ensuring that the diffusion process does not collapse into generating only the most frequent categories. This approach contrasts with methods in the Data and Sampling Strategy Modifications branch, such as Rethinking Noise Sampling[1], which instead recalibrates the noise schedule or sampling procedure to give minority classes more effective training signal. Protecting Minorities[2] also operates in a related vein, emphasizing safeguards that prevent the model from neglecting rare classes. Capacity Manipulation[0] sits squarely in the parameter-level cluster, distinguished by its focus on internal resource reallocation rather than external data reweighting, and it complements works like Protecting Minorities[2] by offering a structural rather than procedural solution to the same imbalance challenge.

Claimed Contributions

Model capacity allocation perspective for imbalanced diffusion models

The authors identify and analyze model capacity allocation as a novel factor affecting diffusion model performance on imbalanced datasets. They provide empirical experiments and theoretical analysis showing that majority classes monopolize model capacity, restricting minority class representation.

10 retrieved papers
Capacity Manipulation (CM) method

The authors propose CM, a method that uses low-rank decomposition of model parameters to reserve capacity for minority classes and introduces a capacity manipulation loss to allocate appropriate capacity during training, enhancing minority class representation without increasing inference overhead.

10 retrieved papers
Theoretical analysis of capacity allocation in diffusion models

The authors provide theoretical analysis (Theorems 2.1 and 3.1) demonstrating how majority classes dominate parameter updates and model capacity, and how low-rank decomposition can mitigate this capacity collapse to improve minority class learning.

10 retrieved papers

Core Task Comparisons

Comparisons with papers in the same taxonomy category

Contribution Analysis

Detailed comparisons for each claimed contribution

Contribution

Model capacity allocation perspective for imbalanced diffusion models

The authors identify and analyze model capacity allocation as a novel factor affecting diffusion model performance on imbalanced datasets. They provide empirical experiments and theoretical analysis showing that majority classes monopolize model capacity, restricting minority class representation.

Contribution

Capacity Manipulation (CM) method

The authors propose CM, a method that uses low-rank decomposition of model parameters to reserve capacity for minority classes and introduces a capacity manipulation loss to allocate appropriate capacity during training, enhancing minority class representation without increasing inference overhead.

Contribution

Theoretical analysis of capacity allocation in diffusion models

The authors provide theoretical analysis (Theorems 2.1 and 3.1) demonstrating how majority classes dominate parameter updates and model capacity, and how low-rank decomposition can mitigate this capacity collapse to improve minority class learning.