[Mosaic] Add abs, sign, erf, atan2, reduce_min, reduce_prod support to mgpu

[oulgen]

Needed to enable more PyTorch Inductor mgpu tests like pytorch/pytorch#171485

[gemini-code-assist]

Summary of Changes

Hello @oulgen, 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 expands the functional capabilities of the Mosaic GPU backend by integrating several fundamental mathematical operations and reduction primitives. These additions are crucial for enhancing JAX's compatibility with PyTorch Inductor, allowing for a broader range of computations to be efficiently compiled and executed on GPUs. The changes involve updating lowering rules, extending the FragmentedArray API, and ensuring robust test coverage for the new functionalities.

Highlights

• New Math Operations: Added support for abs, sign, erf, and atan2 operations within the Mosaic GPU lowering rules.
• Reduction Operations: Introduced support for reduce_min and reduce_prod operations, including their resource estimation and lowering rules for both Lane and Warpgroup semantics.
• FragmentedArray Enhancements: Implemented corresponding abs, sign, erf, atan2, min, and prod methods directly within the FragmentedArray class for efficient GPU execution.
• Comprehensive Testing: Expanded the test suite with new tests for sign, atan2, reduce_min, and reduce_prod, and updated existing unary operation tests to cover abs and erf.

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[gemini-code-assist]

Code Review

This pull request adds support for abs, sign, erf, atan2, reduce_min, and reduce_prod to Mosaic GPU, which is a great enhancement. The implementation looks solid and is accompanied by relevant tests. I have a couple of suggestions to refactor some duplicated code in the lowering rules for better maintainability. Additionally, I've pointed out a missing test case for unsigned integers in the sign operation test.

[oulgen]

I don't have permissions to add reviewers, so here it goes: @sharadmv @voznesenskym @apaszke