ATOM: Asynchronous Training of Massive Models for Deep Learning in a Decentralized Environment (2403.10504v1)

Abstract: The advent of the Transformer architecture has propelled the growth of NLP models, leading to remarkable achievements in numerous NLP tasks. Yet, the absence of specialized hardware like expansive GPU memory and high-speed interconnects poses challenges for training large-scale models. This makes it daunting for many users to experiment with pre-training and fine-tuning LLMs. In this study, we introduce \atom, a resilient distributed training framework designed for asynchronous training of vast models in a decentralized setting using cost-effective hardware, including consumer-grade GPUs and Ethernet. Unlike conventional model partitioning methods that distribute sub-models across GPUs, \atom aims to accommodate a complete LLM on one host (peer) through seamlessly model swapping and concurrently trains multiple copies across various peers to optimize training throughput. Through static analysis, \atom identifies the best model partitioning strategy and flawlessly merges model execution with swapping. Key benefits of \atom include: Avoiding the central point of failure found in pipeline parallelism methods. Demonstrating superior performance and scalability compared to closely-integrated pipeline parallelism in slower networks. Our experiments using different GPT-3 model configurations reveal that, in scenarios with suboptimal network connections, \atom can enhance training efficiency up to $20 \times$ when juxtaposed with the state-of-the-art decentralized pipeline parallelism approaches.

Asynchronous Training of Massive Models in Decentralized Environments with Atom

Introduction to Atom

The continual growth of LLMs like GPT-3 necessitates an evolution in training methodologies, especially for entities lacking specialized hardware. Conventional distributed training approaches, while effective, demand substantial hardware resources and optimized network conditions, limiting access for a broader user base. Atom represents a novel approach, sidestepping these restrictions by facilitating the training of vast models in decentralized settings on cost-effective hardware. Unlike standard partitioning that distributes a model across GPUs, Atom proposes a model where each host (peer) accommodates a complete LLM through model swapping, optimizing the training process across multiple peers for enhanced throughput.

Challenges in LLM Training

The introduction of Transformer models has remarkably progressed the capabilities of deep neural networks, enabling groundbreaking successes in NLP. However, the training of these models, due to their enormity, requires substantial computational resources that surpass the development of conventional hardware. Training from scratch further accentuates the challenge, necessitating methodologies that allow the use of LLMs without resorting to massive accelerator farms.

Atom's Approach to Distributed Training

Atom's infrastructure diverges from existing model and pipeline parallelism by housing a complete model within a server's memory. This method, pioneering within the context of distributed LLM training, leverages memory swapping to facilitate model execution on singular GPUs. Atom's design prioritizes preventing GPU idleness, adeptly managing the trade-off between computation and memory swapping.

Characterization of GPT-3 for Atom

Critical to Atom's approach is a detailed profiling of the GPT-3 model to understand its memory and execution demands. Through profiling, Atom determines that even the most intensive layers of GPT-3 can be accommodated within a single consumer-grade GPU. This discovery underpins Atom's strategy of exploiting the individual operator/layer fitting within GPU memory, averting the need for extensive model partitioning.

Streamlining Memory Swapping

Atom addresses memory swapping's traditional overhead by establishing an optimal schedule that aligns model execution with swapping. This involves extending the forward propagation phase to match sub-model loading times, leveraging gradient accumulation. Particularly notable is Atom's handling of the embedding layer, a considerable but computationally minimal component, ensuring its efficient utilization without impeding performance.

Implementation Insights

Implemented on Pytorch and leveraging Hivemind for decentralized coordination, Atom encapsulates model tracing, partitioning, and compilation into a streamlined process. This process effectively divides the model into sub-models for independent training across peers, synchronizing through periodic allreduce communication.

Evaluation and Findings

Empirical assessments underscore Atom's superior performance in scenarios constrained by suboptimal network conditions, showcasing up to a 20x enhancement in training efficiency over decentralized pipeline parallelism methods. These evaluations also affirm Atom's scalability and effectiveness in maintaining convergence amidst dynamic changes, such as node failures or varying network conditions.

Concluding Remarks

Atom emerges as a robust framework for the asynchronous training of large-scale models within decentralized environments, mitigating the steep hardware requisites traditionally associated with such tasks. It not only demonstrates practical scalability and efficiency but also ensures model training effectiveness is kept intact, paving the way for broader accessibility to high-quality AI model training.