⚡️ Speed up method Categorical.equals by 1,129%

[codeflash-ai]

📄 1,129% (11.29x) speedup for Categorical.equals in pandas/core/arrays/categorical.py

⏱️ Runtime : 155 microseconds → 12.6 microseconds (best of 17 runs)

📝 Explanation and details

The optimized code achieves a 12x speedup by eliminating expensive hash computations and avoiding unnecessary object allocations in the equals method.

Key optimizations:

1. Early reference equality check: Added if self is other: return True to immediately return for identical objects - a common case in pandas workflows where the same Categorical is compared to itself.

2. Avoided expensive hash computation: The original code called hash(self.dtype) == hash(other.dtype) which is computationally expensive. The optimized version:

   • First checks if dtype objects are identical (self_dtype is other_dtype)
   • Then directly compares .ordered fields and uses Index.equals() for categories comparison
   • Only falls back to hash comparison as a last resort

3. Inlined recoding logic: Instead of calling self._encode_with_my_categories(other) which creates a temporary Categorical object, the optimized version directly calls recode_for_categories() and compares codes, eliminating object allocation overhead.

4. Optimized _categories_match_up_to_permutation: Similarly avoids hash computation by doing direct field comparisons first.

Performance characteristics: These optimizations are particularly effective for:

• Cases where categoricals have identical dtypes (common in pandas operations)
• Self-comparisons (cat.equals(cat))
• Comparisons between categoricals with the same category structure

The line profiler shows the original hash() call took 196ms (100% of time), while the optimized version's field comparisons take only 27ms (70% of total time), with the overall method running 12x faster.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 78 Passed
🌀 Generated Regression Tests	🔘 None Found
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	66.7%

⚙️ Existing Unit Tests and Runtime

Test File::Test Function	Original ⏱️	Optimized ⏱️	Speedup
arrays/categorical/test_operators.py::TestCategoricalOps.test_compare_unordered_different_order	154μs	12.6μs	1129%✅

To edit these changes git checkout codeflash/optimize-Categorical.equals-mhby1z89 and push.