Summary

Refactored the combine method in GasInfo to use more efficient entry-based operations instead of creating new collections. The new implementation directly updates the existing variable_values and function_costs maps by iterating through the entries of the other GasInfo instance and adding values to the corresponding entries or inserting new ones when needed.

Type of change

Please check one:

• Bug fix (fixes incorrect behavior)
• New feature
• Performance improvement
• Documentation change with concrete technical impact
• Style, wording, formatting, or typo-only change

Why is this change needed?

The previous implementation of combine was inefficient as it created new collections by first collecting unique keys from both maps, then creating new entries with combined values. This approach involved unnecessary allocations and computations. The new implementation directly updates the existing maps, reducing memory allocations and improving performance.

What was the behavior or documentation before?

The previous implementation created new collections by collecting unique keys, swapping out values, and building new maps from scratch, which was less efficient.

What is the behavior or documentation after?

The new implementation maintains the same functionality but uses the Entry API to directly update the existing maps in-place, reducing allocations and improving performance. It also adds a descriptive comment about the method's purpose.

Additional context

This change is part of ongoing performance optimizations in the Sierra gas calculation system. The functionality remains identical, but the implementation is more efficient.