axiom-energy-ref

# Energy Optimization Reference

Complete API reference for iOS energy optimization, with code examples from WWDC sessions and Apple documentation.

**Related skills**: `axiom-energy` (decision trees, patterns), `axiom-energy-diag` (troubleshooting)

---

## Part 1: Power Profiler Workflow

### Recording a Trace with Instruments

#### Tethered Recording (Connected to Mac)

```
1. Connect iPhone wirelessly to Xcode
   - Xcode → Window → Devices and Simulators
   - Enable "Connect via network" for your device

2. Profile your app
   - Xcode → Product → Profile (Cmd+I)
   - Select Blank template
   - Click "+" → Add "Power Profiler"
   - Optionally add "CPU Profiler" for correlation

3. Record
   - Select your app from target dropdown
   - Click Record (red button)
   - Use app normally for 2-3 minutes
   - Click Stop

4. Analyze
   - Expand Power Profiler track
   - Examine per-app lanes: CPU, GPU, Display, Network
```

**Important**: Use wireless debugging. When device is charging via cable, system power usage shows 0.

#### On-Device Recording (Without Mac)

From WWDC25-226: Capture traces in real-world conditions.

```
1. Enable Developer Mode
   Settings → Privacy & Security → Developer Mode → Enable

2. Enable Performance Trace
   Settings → Developer → Performance Trace → Enable
   Set tracing mode to "Power Profiler"
   Toggle ON your app in the app list

3. Add Control Center shortcut
   Control Center → Tap "+" → Add a Control → Performance Trace

4. Record
   Swipe down → Tap Performance Trace icon → Start
   Use app (can record up to 10 hours)
   Tap Performance Trace icon → Stop

5. Share trace
   Settings → Developer → Performance Trace
   Tap Share button next to trace file
   AirDrop to Mac or email to developer
```

### Interpreting Power Profiler Metrics

| Lane | Meaning | What High Values Indicate |
|------|---------|--------------------------|
| System Power | Overall battery drain rate | General energy consumption |
| CPU Power Impact | Processor