Use FlattenMapper before codegen

[inducer]

• Smaller expressions to crunch through
• Throws off flop counts

[Copilot]

Pull request overview

This pull request adds the FlattenMapper from pymbolic to the expression transformation pipeline before code generation to process smaller expressions. The kernel cache version is incremented to ensure regeneration of cached kernels with the new transformation logic.

Changes:

• Add FlattenMapper to the mapper chain in to_loopy_insns to flatten expressions before other transformations
• Increment kernel cache version from 1 to 2 to invalidate cached kernels

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
sumpy/codegen.py	Import FlattenMapper and apply it as the first transformation in the mapper chain
sumpy/version.py	Increment kernel cache version to force regeneration of cached kernels

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.