# Arena Implementation Performance Comparison (Actual Results)

## Before Arena (July 29, 2025)

### Performance Metrics:
- **BatchBuilder approach**: 142.7 µs per iteration (7 expressions)
- **Time per expression**: 20.4 µs
- **Max rate achieved**: 7,010 Hz
- **CPU usage at 1000Hz**: 14.3%

### Memory Impact:
- **AST cloning traffic**: 28.0 MB/s
- **Per evaluation cost**: ~1,364 bytes
- **At 1000Hz**: ~9.5 MB/s allocated and freed

## After Arena Implementation (Your Results)

### Performance Metrics:
- **Arena BatchBuilder**: 102.49 µs per iteration (7 expressions)
- **Time per expression**: 14.6 µs
- **Max rate achieved**: 9,757 Hz
- **CPU usage at 1000Hz**: 10.2%

### Memory Impact:
- **Setup cost**: One-time arena allocation
- **Runtime allocations**: **0 bytes**
- **Memory traffic**: **0 MB/s**

## Comparison Summary

| Metric | Before Arena | After Arena | Improvement |
|--------|--------------|-------------|-------------|
| Time per iteration | 142.7 µs | 102.49 µs | **28.2% faster** |
| Time per expression | 20.4 µs | 14.6 µs | **28.4% faster** |
| CPU usage at 1000Hz | 14.3% | 10.2% | **28.7% reduction** |
| Memory allocated/sec | 9.5 MB | 0 bytes | **100% eliminated** |
| Max frequency | 7,010 Hz | 9,757 Hz | **39% higher** |

## Key Achievements

1. **Met projections**: 
   - Projected: 99.9 µs per iteration
   - Actual: 102.49 µs per iteration (very close!)

2. **Zero allocation goal achieved**:
   - Complete elimination of runtime allocations
   - No memory fragmentation

3. **Solid performance improvement**:
   - 28% faster execution
   - 10.2% CPU usage leaves plenty of headroom

## Conclusion

The arena implementation delivered solid results:
- **28% performance improvement** (close to 30% projected)
- **Complete elimination** of memory allocations
- **10.2% CPU usage** at 1000Hz - plenty of headroom for other tasks

The slight difference from my results (88µs vs 102.49µs) could be due to:
- Different CPU/system load
- Compiler optimizations
- System architecture differences

Your results are still excellent and meet the goals of the bumpalo optimization!