chore

ISSUE_159_CONCLUSION.md

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-# Issue #159 Performance Analysis - Conclusion
-
-## Problem Summary
-User reported search times of 15-30 seconds instead of the ~2 seconds mentioned in the paper.
-
-**Configuration:**
-- GPU: 4090×1
-- Embedding Model: BAAI/bge-large-zh-v1.5 (~300M parameters)
-- Data Size: 180MB text (~90K chunks)
-- Backend: HNSW
-- beam_width: 10
-- Other parameters: Default values
-
-## Root Cause Analysis
-
-### 1. **Search Complexity Parameter**
-The **default `complexity` parameter is 64**, which is too high for achieving ~2 second search times with this configuration.
-
-**Test Results (Reproduced):**
-- **Complexity 64 (default)**: **36.17 seconds** ❌
-- **Complexity 32**: **2.49 seconds** ✅
-- **Complexity 16**: **2.24 seconds** ✅ (Close to paper's ~2 seconds)
-- **Complexity 8**: **1.67 seconds** ✅
-
-### 2. **beam_width Parameter**
-The `beam_width` parameter is **mainly for DiskANN backend**, not HNSW. Setting it to 10 has minimal/no effect on HNSW search performance.
-
-### 3. **Embedding Model Size**
-The paper uses a smaller embedding model (~100M parameters), while the user is using `BAAI/bge-large-zh-v1.5` (~300M parameters). This contributes to slower embedding computation during search, but the main bottleneck is the search complexity parameter.
-
-## Solution
-
-### **Recommended Fix: Reduce Search Complexity**
-
-To achieve search times close to ~2 seconds, use:
-
-```python
-from leann.api import LeannSearcher
-
-searcher = LeannSearcher(INDEX_PATH)
-results = searcher.search(
-    query="your query",
-    top_k=10,
-    complexity=16,  # or complexity=32 for slightly better accuracy
-    # beam_width parameter doesn't affect HNSW, can be ignored
-)
-```
-
-Or via CLI:
-```bash
-leann search your-index "your query" --complexity 16
-```
-
-### **Alternative Solutions**
-
-1. **Use DiskANN Backend** (Recommended by maintainer)
-   - DiskANN is faster for large datasets
-   - Better performance scaling
-   - `beam_width` parameter is relevant here
-   ```python
-   builder = LeannBuilder(backend_name="diskann")
-   ```
-
-2. **Use Smaller Embedding Model**
-   - Switch to a smaller model (~100M parameters) like the paper
-   - Faster embedding computation
-   - Example: `BAAI/bge-base-zh-v1.5` instead of `bge-large-zh-v1.5`
-
-3. **Disable Recomputation** (Trade storage for speed)
-   - Use `--no-recompute` flag
-   - Stores all embeddings (much larger storage)
-   - Faster search (no embedding recomputation)
-   ```bash
-   leann build your-index --no-recompute --no-compact
-   leann search your-index "query" --no-recompute
-   ```
-
-## Performance Comparison
-
-| Complexity | Search Time | Accuracy | Recommendation |
-|------------|-------------|----------|---------------|
-| 64 (default) | ~36s | Highest | ❌ Too slow |
-| 32 | ~2.5s | High | ✅ Good balance |
-| 16 | ~2.2s | Good | ✅ **Recommended** (matches paper) |
-| 8 | ~1.7s | Lower | ⚠️ May sacrifice accuracy |
-
-## Key Takeaways
-
-1. **The default `complexity=64` is optimized for accuracy, not speed**
-2. **For ~2 second search times, use `complexity=16` or `complexity=32`**
-3. **`beam_width` parameter is for DiskANN, not HNSW**
-4. **The paper's ~2 second results likely used:**
-   - Smaller embedding model (~100M params)
-   - Lower complexity (16-32)
-   - Possibly DiskANN backend
-
-## Verification
-
-The issue has been reproduced and verified. The test script `test_issue_159.py` demonstrates:
-- Default complexity (64) results in ~36 second search times
-- Reducing complexity to 16-32 achieves ~2 second search times
-- This matches the user's reported issue and provides a clear solution
-
-## Next Steps
-
-1. ✅ Issue reproduced and root cause identified
-2. ✅ Solution provided (reduce complexity parameter)
-3. ⏳ User should test with `complexity=16` or `complexity=32`
-4. ⏳ Consider updating documentation to clarify complexity parameter trade-offs
-