Fix block dimensions consistency

[igor-holt]

Fixed inconsistency where single-block scalar states were not expanded to have a leading dimension. Removed special handling for len(collected) == 1 to always use _stack. Added regression test.

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PR created automatically by Jules for task 10423846750295347954 started by @igor-holt

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[gemini-code-assist]

Summary of Changes

Hello @igor-holt, 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 addresses an inconsistency in how block dimensions were handled, specifically for scalar states within single blocks. By standardizing the dimension expansion, it ensures that all states, regardless of the number of blocks, maintain a consistent shape, thereby improving the robustness and predictability of the block_management system.

Highlights

• Dimension Consistency: Ensured that single-block scalar states are consistently expanded to have a leading dimension (e.g., () to (1,)) to match multi-block states.
• Simplified Logic: Removed special conditional handling for single-block collections in block_state_to_global, now always using jax.tree.map(_stack, *collected).
• Regression Test: Added a new test file (tests/test_block_management_scalar.py) to verify the correct shape expansion for scalar states in both single and multi-block scenarios.

Changelog

• tests/test_block_management_scalar.py
  • Added a new test file test_block_management_scalar.py to validate the shape of scalar states in single and multi-block configurations.
• thrml/block_management.py
  • Modified the block_state_to_global function to remove special handling for single-element collected lists, ensuring jax.tree.map(_stack, *collected) is always used.

Activity

• PR created automatically by Jules for task 10423846750295347954, started by @igor-holt.

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[gemini-code-assist]

Code Review

This pull request addresses an inconsistency in how scalar states are handled for single blocks. By removing the special case for a single collected state in block_state_to_global and always using jax.tree.map with _stack, the code now correctly expands scalar states to have a leading dimension, making their shape (1,) instead of (). This improves consistency with multi-block states which are stacked into shapes like (N,). The change simplifies the code and removes a TODO comment. A new regression test has been added to verify this fix, covering both single and multi-block scenarios. The implementation is clean and the test is comprehensive. This is a great improvement.