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This PR introduces support for tensor parallelism autosharding in Keras, enabling users to shard large model layers across multiple devices. This is a crucial feature for training models that are too large to fit into the memory of a single accelerator.

The implementation is centered around two new components:

autoconfig.py: This module contains the logic to analyze a Keras model, identify sharding candidates (e.g., Dense, EinsumDense layers), and generate a sharding plan.

coordinated_optimizer.py: This is an optimizer wrapper that consumes the sharding plan. During training, it intercepts gradients for sharded variables and performs a collective AllReduce to ensure weight updates are correctly synchronized across all devices.

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Summary of Changes

Hello @buildwithsuhana, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances Keras's capabilities for large-scale model training by introducing foundational support for tensor parallelism autosharding. It provides mechanisms to automatically determine how model layers should be split across multiple devices and a specialized optimizer to manage the distributed training process, including sharding optimizer states and synchronizing gradients. This enables users to train models that exceed the memory capacity of a single accelerator, making distributed training more accessible and efficient within the Keras ecosystem.

Highlights

  • Automatic Sharding Configuration: Introduced "autoconfig.py" to intelligently analyze Keras models (e.g., Dense, EinsumDense, Embedding layers) and generate a tensor parallelism sharding plan, classifying Dense layers as "up-projection" or "down-projection" for optimal splitting.
  • Coordinated Optimizer for Distributed Training: Added "coordinated_optimizer.py" which provides "CoordinatedOptimizer" for managing sharded optimizer states and synchronizing gradients across devices, and "TensorParallelOptimizer" as a Keras-compatible wrapper.
  • Gradient Synchronization Logic: The "CoordinatedOptimizer" includes logic to perform "all-reduce" operations on gradients of column-parallel sharded weights, ensuring correct updates in a distributed setting.
  • Optimizer State Sharding: Implemented functionality to partition optimizer state variables (like momentum and velocity) across multiple devices, reducing memory footprint per device.
  • Comprehensive Testing: New test files ("autoconfig_test.py", "coordinated_optimizer_test.py") were added to validate the automatic sharding configuration and the distributed optimizer's behavior, including handling of replicated and sharded states, and serialization.
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Code Review

This pull request introduces significant new functionality for tensor parallelism autosharding in Keras, including modules for automatic configuration and a coordinated optimizer. The implementation is well-structured, with new logic for analyzing models, generating sharding plans, and synchronizing gradients. However, I've identified a few issues that need attention. There is a critical bug in the CoordinatedOptimizer where a method for applying gradients with sharded states is called but not defined. I also found a couple of high-severity issues related to incorrect logic for matching optimizer states and gathering sharded parameters, which could lead to runtime errors or incorrect behavior. Additionally, there are some medium-severity issues regarding code clarity, such as unused parameters. The accompanying tests are a good start but do not cover the code path with the critical bug.

@buildwithsuhana buildwithsuhana marked this pull request as draft October 2, 2025 17:28
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