@mytec: diag iter3.2.2

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# RFCP - Iteration 3.2.2: Dominant Path Performance Diagnostic
## Overview
LOD is working (5 buildings instead of 25) but performance is still ~340ms/point.
This should be ~15x faster but it's almost the same speed. Need to find the bottleneck.
**Observed:**
```
[DOMINANT_PATH_VEC] Point #1: buildings=5, walls=50, dist=2946m
338.8ms/point average
```
**Expected:**
```
5 buildings × 50 walls should be ~20-30ms/point, not 340ms
```
---
## Task 1: Add Detailed Timing to Dominant Path
**File:** `backend/app/services/dominant_path_service.py`
Add timing breakdown to understand where time is spent:
```python
import time
import logging
logger = logging.getLogger(__name__)
def find_dominant_path_with_lod(
tx_lat: float, tx_lon: float, tx_height: float,
rx_lat: float, rx_lon: float, rx_height: float,
frequency_mhz: float,
buildings: list,
distance_m: float = None,
spatial_idx = None, # May be passed in
) -> dict:
"""Find dominant path with LOD and detailed timing."""
timings = {}
t_total_start = time.perf_counter()
# 1. Distance calculation
t_start = time.perf_counter()
if distance_m is None:
from app.services.terrain_service import TerrainService
distance_m = TerrainService.haversine_distance(tx_lat, tx_lon, rx_lat, rx_lon)
timings['distance_calc'] = (time.perf_counter() - t_start) * 1000
# 2. LOD level determination
t_start = time.perf_counter()
lod = get_lod_level(distance_m)
timings['lod_check'] = (time.perf_counter() - t_start) * 1000
# 3. Early return for LOD_NONE
if lod == LODLevel.NONE:
timings['total'] = (time.perf_counter() - t_total_start) * 1000
logger.debug(f"[DP_TIMING] LOD_NONE dist={distance_m:.0f}m total={timings['total']:.2f}ms")
return {
"path_loss_db": 0.0,
"lod_level": "none",
"buildings_checked": 0,
"walls_checked": 0,
"skipped": True,
"timings": timings
}
# 4. Building filtering for LOD_SIMPLIFIED
t_start = time.perf_counter()
buildings_to_check = buildings
if lod == LODLevel.SIMPLIFIED and buildings:
# This filtering might be slow!
if len(buildings) > SIMPLIFIED_MAX_BUILDINGS:
mid_lat = (tx_lat + rx_lat) / 2
mid_lon = (tx_lon + rx_lon) / 2
buildings_with_dist = []
for b in buildings:
geom = b.get('geometry', {})
coords = geom.get('coordinates', [[]])[0] if isinstance(geom, dict) else b.get('geometry', [[]])
if coords and len(coords) > 0:
if isinstance(coords[0], (list, tuple)):
blat = sum(c[1] for c in coords) / len(coords)
blon = sum(c[0] for c in coords) / len(coords)
else:
blat = sum(c.get('lat', c.get('y', 0)) for c in coords) / len(coords)
blon = sum(c.get('lon', c.get('x', 0)) for c in coords) / len(coords)
from app.services.terrain_service import TerrainService
dist = TerrainService.haversine_distance(mid_lat, mid_lon, blat, blon)
buildings_with_dist.append((dist, b))
buildings_with_dist.sort(key=lambda x: x[0])
buildings_to_check = [b for _, b in buildings_with_dist[:SIMPLIFIED_MAX_BUILDINGS]]
timings['building_filter'] = (time.perf_counter() - t_start) * 1000
# 5. Wall extraction
t_start = time.perf_counter()
# ... wall extraction code ...
timings['wall_extraction'] = (time.perf_counter() - t_start) * 1000
# 6. Geometry calculations (intersections, reflections)
t_start = time.perf_counter()
# ... geometry code ...
timings['geometry_calc'] = (time.perf_counter() - t_start) * 1000
# Total
timings['total'] = (time.perf_counter() - t_total_start) * 1000
# Log timing breakdown
logger.info(
f"[DP_TIMING] LOD={lod.value} dist={distance_m:.0f}m "
f"bldgs={len(buildings_to_check)} "
f"filter={timings.get('building_filter', 0):.1f}ms "
f"walls={timings.get('wall_extraction', 0):.1f}ms "
f"geom={timings.get('geometry_calc', 0):.1f}ms "
f"total={timings['total']:.1f}ms"
)
result["timings"] = timings
return result
```
---
## Task 2: Check if Building Filtering is the Bottleneck
The LOD_SIMPLIFIED filtering iterates through ALL 15000 buildings to find 5 nearest.
This is O(n) for every point!
**Potential fix - use spatial index:**
```python
# Instead of iterating all buildings:
if spatial_idx is not None:
# Use spatial index to get nearby buildings quickly
nearby = spatial_idx.query_radius(mid_lat, mid_lon, radius=500) # 500m radius
buildings_to_check = nearby[:SIMPLIFIED_MAX_BUILDINGS]
else:
# Fallback to slow method
...
```
---
## Task 3: Check Coverage Service Integration
**File:** `backend/app/services/coverage_service.py`
Find where dominant_path is called and check:
1. Is spatial_idx being passed?
2. Is building list pre-filtered or full 15000?
3. Are buildings being re-processed for each point?
Look for patterns like:
```python
# BAD - full list passed to every point
for point in points:
result = find_dominant_path_with_lod(..., buildings=all_buildings)
# GOOD - pre-filter by distance to point
for point in points:
nearby = spatial_idx.query(point)
result = find_dominant_path_with_lod(..., buildings=nearby)
```
---
## Task 4: Add Summary Statistics
At the end of coverage calculation, log timing summary:
```python
# In coverage_service.py after all points calculated:
if timing_data:
avg_filter = sum(t.get('building_filter', 0) for t in timing_data) / len(timing_data)
avg_geom = sum(t.get('geometry_calc', 0) for t in timing_data) / len(timing_data)
avg_total = sum(t.get('total', 0) for t in timing_data) / len(timing_data)
logger.info(
f"[DP_SUMMARY] {len(timing_data)} points: "
f"avg_filter={avg_filter:.1f}ms, avg_geom={avg_geom:.1f}ms, "
f"avg_total={avg_total:.1f}ms"
)
```
---
## Task 5: Quick Win - Skip Filtering for LOD_NONE
Make sure LOD_NONE returns IMMEDIATELY without touching buildings list:
```python
def find_dominant_path_with_lod(...):
# FIRST thing - check LOD
if distance_m is None:
distance_m = calculate_distance(...)
lod = get_lod_level(distance_m)
# IMMEDIATE return for LOD_NONE - don't even look at buildings
if lod == LODLevel.NONE:
return {"path_loss_db": 0.0, "skipped": True, "lod_level": "none"}
# Only now process buildings...
```
---
## Expected Output
After implementing, logs should show:
```
[DP_TIMING] LOD=none dist=4500m total=0.05ms
[DP_TIMING] LOD=simplified dist=2500m bldgs=5 filter=250.0ms walls=2.0ms geom=5.0ms total=258.0ms
[DP_TIMING] LOD=full dist=800m bldgs=25 filter=0.0ms walls=5.0ms geom=50.0ms total=56.0ms
```
This will show us exactly where the 340ms is being spent.
---
## Suspected Root Cause
**Building filtering is O(15000) for every point!**
Even with LOD_SIMPLIFIED, we iterate through 15000 buildings to find 5 nearest.
868 points × 15000 buildings = 13 million iterations just for filtering!
**Fix:** Use spatial index to get nearby buildings in O(log n) instead of O(n).
---
## Testing
After implementing diagnostics:
```powershell
cd D:\root\rfcp\installer
.\test-detailed-quick.bat
```
Check logs for `[DP_TIMING]` and `[DP_SUMMARY]` lines.
---
## Success Criteria
1. Logs show timing breakdown for each component
2. Identify which step takes most time (filter vs geometry)
3. If filter is slow → implement spatial index fix
4. If geometry is slow → investigate vectorized calculations
---
*"You can't optimize what you can't measure"*