Aot

[danielsuo]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @danielsuo, 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 introduces a foundational Ahead-of-Time (AOT) compilation API into JAX, enabling the definition and efficient caching of computational components. The primary goal is to optimize performance by reducing redundant compilations and facilitating the reuse of pre-compiled graph segments. This is achieved through new modules for component definition and sophisticated caching utilities, alongside targeted modifications to JAX's core tracing and compilation infrastructure to seamlessly integrate AOT capabilities.

Highlights

• New AOT Component API: Introduced jax._src.aot.py with a component decorator to define reusable, cacheable computational graphs, including its primitive implementation, abstract evaluation, lowering, and batching rules.
• AOT Caching Utilities: Added jax._src.aot_util.py providing ComponentKey, CacheEntry, and Cache classes to manage and serialize AOT component states and compiled modules, along with utilities for function transformations and state management.
• Enhanced JAX Caching: Modified jax._src.linear_util.py to augment the cache decorator with hit tracking (hit_caches) and additional introspection methods (cache_items, cache_get, cache_keys, hit_get), crucial for the new AOT caching mechanism.
• Pjit Integration and Caching Improvements: Updated jax/_src/pjit.py with logging for cache behavior in _cpp_pjit and _infer_params_internal, and introduced a new internal cache for _infer_params_internal, indicating deeper integration with JAX's pjit compilation.
• Tracing API Refinement: jax._src.api.py now includes a dedicated trace function, which eval_shape utilizes, streamlining the tracing process for AOT components.
• Comprehensive Testing: A new ComponentTest class in tests/aot_test.py validates the aot.component decorator's functionality, including its interaction with jit, vmap, and detailed cache management, ensuring the robustness of the new API.

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[gemini-code-assist]

Code Review

This pull request introduces a new experimental Ahead-of-Time (AOT) compilation API, centered around the @aot.component decorator. The changes are substantial, adding new files for the AOT logic and utilities, and modifying existing files to support caching and testing.

While this is a promising feature, the implementation appears to be in an early stage and has several critical issues that need to be addressed. For example, there's an incorrect equality implementation in ComponentKey, a module-level cache in pjit.py that will cause memory leaks and is not thread-safe, and a bug in traceback_util.py where a casted variable is not returned. Additionally, the code contains numerous TODO comments and debug logging statements that should be cleaned up. The hardcoding of platforms=["cpu"] also severely limits the current implementation.

[gemini-code-assist]

A module-level dictionary cache is used for caching in _infer_params_internal. This is problematic for several reasons:

1. Memory Leak: The cache has no eviction policy and will grow indefinitely, leading to a memory leak.
2. Thread Safety: A global mutable dictionary is not thread-safe. In a multi-threaded environment, this can lead to race conditions.

A proper caching mechanism should be used, such as functools.lru_cache or a custom cache implementation that handles thread safety and eviction.

[gemini-code-assist]

The platforms argument is hardcoded to ["cpu"], which limits this AOT functionality to only the CPU backend. The associated TODO indicates this is a known issue. This should be resolved to correctly use the platform context from the lowering context (ctx.platforms) to support other backends like GPU and TPU.

[gemini-code-assist]

The casted variable is created but the original reraise_with_filtered_traceback is returned. This is likely a bug. The surrounding logging statements also appear to be for debugging and can be removed. The code can be simplified to return the casted value directly.

Suggested change

	casted = cast(C, reraise_with_filtered_traceback)
	if hasattr(fun, '__name__') and 'wrapper' in fun.__name__:
	logging.info("casted reraise id %s",
	id(casted))
	return reraise_with_filtered_traceback
	return cast(C, reraise_with_filtered_traceback)

[gemini-code-assist]

This and other logging.info statements throughout the changes appear to be for debugging. They should be removed before merging to avoid polluting user logs.