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MoEC: Mixture of Experts Implicit Neural Compression (2312.01361v1)

Published 3 Dec 2023 in cs.CV, cs.LG, and eess.IV

Abstract: Emerging Implicit Neural Representation (INR) is a promising data compression technique, which represents the data using the parameters of a Deep Neural Network (DNN). Existing methods manually partition a complex scene into local regions and overfit the INRs into those regions. However, manually designing the partition scheme for a complex scene is very challenging and fails to jointly learn the partition and INRs. To solve the problem, we propose MoEC, a novel implicit neural compression method based on the theory of mixture of experts. Specifically, we use a gating network to automatically assign a specific INR to a 3D point in the scene. The gating network is trained jointly with the INRs of different local regions. Compared with block-wise and tree-structured partitions, our learnable partition can adaptively find the optimal partition in an end-to-end manner. We conduct detailed experiments on massive and diverse biomedical data to demonstrate the advantages of MoEC against existing approaches. In most of experiment settings, we have achieved state-of-the-art results. Especially in cases of extreme compression ratios, such as 6000x, we are able to uphold the PSNR of 48.16.

Citations (3)

Summary

  • The paper introduces MoEC, a novel method that uses a mixture of experts approach to adaptively compress complex 3D and 4D biomedical data.
  • It leverages an intelligent router and a shared encoder-decoder to optimize data partitioning and maintain high reconstruction fidelity, achieving superior PSNR and SSIM scores compared to TINC and HEVC.
  • The training strategy incorporates balancing loss and expert capacity constraints to evenly distribute workloads, enabling effective compression even at extreme ratios up to 6000x.

MoEC: An Adaptive Compression Method for 3D and 4D Biomedical Data

Introduction

Imagine trying to compress massive biomedical datasets without losing any critical information. Traditional compression methods often struggle with such tasks, particularly when it comes to 3D or 4D data. Enter MoEC (Mixture of Experts Compression), a novel method designed to tackle this exact challenge.

MoEC employs a Mixture of Experts (MoE) strategy, which is basically a team of specialized neural networks working together. Each expert focuses on a different part of the data, and a "router" decides which expert deals with which data segment. This setup allows MoEC to adaptively partition and compress complex biomedical data without needing hand-crafted rules.

Key Components and Methodology

Intelligent Router and Expert Networks

At its core, MoEC comprises:

  1. An Intelligent Router: This network decides which parts of the data should be managed by which experts.
  2. Expert Networks: Set of specialized neural networks, each designed to compress specific segments of the data.
  3. Shared Encoder-Decoder: Transforms and reconstructs data, leveraging information from all expert networks to ensure a faithful representation of the original data.

Let's break down the operation:

  • Routing: The router network intelligently assigns data points to the most suitable expert.
  • Compression by Experts: Each expert receives its designated data points, compresses them using an optimized compression routine involving fully-connected layers and sinusoidal activation functions.
  • Reconstruction: A shared decoder uses the combined outputs of all experts to reconstruct the original data.

Training Strategy

Training an MoEC model isn't straightforward because it involves balancing the workload among all experts. To tackle this, the paper introduces:

  • Balancing Loss: Ensures all experts get properly trained by penalizing imbalance in load among experts.
  • Expert Capacity: Limits how much data an expert can process, ensuring even workload distribution.
  • Uniform Dispatch: Optimizes the shipping of data points to experts, keeping the training process efficient.

Experimental Results

Low Compression Ratios

The MoEC method was tested on various organ datasets (lung, heart, kidney, brain) with compression ratios ranging from 64x to 1024x. The results were impressive:

  • PSNR and SSIM Metrics: These metrics quantify the fidelity of the reconstructed data. MoEC consistently delivered higher PSNR and SSIM values compared to existing methods like TINC and HEVC.
  • Comparison with TINC and HEVC: MoEC demonstrated reduced block artifacts and better preservation of high-frequency details, such as edges between organs and backgrounds.

High Compression Ratios

When pushed to compression ratios as extreme as 6000x, MoEC still held strong:

  • State-of-the-Art Performance: At high compression ratios, MoEC outperformed INR-based methods (like TINC) and codec methods (like HEVC), which typically suffered from severe block artifacts and loss of information in critical frames.
  • Practical Implications: This robustness makes MoEC particularly well-suited for medical imaging applications where data fidelity is crucial.

Ablation Studies

To further validate the contributions of different components in MoEC, the authors conducted ablation studies:

  • Effect of Top-k Route: They found using more routes (Top-2) allowed the network to generalize better, although it required more computational resources.
  • Balancing Loss: Showed significant improvements in ensuring that all expert networks contribute to the final compressed output.
  • Number of Experts: Increasing the number of experts didn't necessarily lead to better performance, emphasizing the importance of optimal parameter distribution among experts.

Implications and Future Directions

This work presents a solid step forward in the compression of high-dimensional biomedical data. In essence, MoEC's adaptive approach to partitioning and compressing data paves the way for more efficient storage and transmission of massive biomedical datasets.

Some potential future developments could include:

  • Scalability: Extending MoEC to handle even larger datasets across more varied domains.
  • Automated Optimization: Developing algorithms that automatically tune the number of experts and their configurations based on the dataset characteristics.
  • Real-Time Applications: Adapting MoEC for real-time data compression tasks in medical imaging and other technology-intensive fields.

MoEC's adaptable and robust design highlights the growing prowess of neural networks in tackling complex and practical problems in data compression. This work exemplifies how we can leverage specialized AI components to improve performance in highly demanding applications.