docs(readme): add Benchmarks section with run steps, report paths, an… (#7)

Author: beinan

rust/lance-graph/README.md

@@ -125,6 +125,41 @@ Most APIs return `Result<T, GraphError>`. Errors include parsing failures, missi
 cargo test -p lance-graph
 ```
 
+## Benchmarks
+
+- **Requirements**:
+  - **protoc**: install `protobuf-compiler` (Debian/Ubuntu: `sudo apt-get install -y protobuf-compiler`).
+  - Optional: **gnuplot** for Criterion's gnuplot backend; otherwise the plotters backend is used.
+
+- **Run** (from `rust/lance-graph`):
+
+```bash
+cargo bench --bench graph_execution
+
+# Quicker local run (shorter warm-up/measurement):
+cargo bench --bench graph_execution -- --warm-up-time 1 --measurement-time 2 --sample-size 10
+```
+
+- **Reports**:
+  - Global index: `rust/lance-graph/target/criterion/report/index.html`
+  - Group index: `rust/lance-graph/target/criterion/cypher_execution/report/index.html`
+
+- **Typical results** (x86_64, quick run: warm-up 1s, measurement 2s, sample size 10):
+
+| Benchmark                           | Size      | Median time | Approx. throughput |
+|-------------------------------------|-----------|-------------|--------------------|
+| `basic_node_filter`                 | 100       | ~680 µs     | ~147 Kelem/s       |
+| `basic_node_filter`                 | 10,000    | ~715 µs     | ~13.98 Melem/s     |
+| `basic_node_filter`                 | 1,000,000 | ~743 µs     | ~1.35 Gelem/s      |
+| `single_hop_expand`                 | 100       | ~2.79 ms    | ~35.9 Kelem/s      |
+| `single_hop_expand`                 | 10,000    | ~3.77 ms    | ~2.65 Melem/s      |
+| `single_hop_expand`                 | 1,000,000 | ~3.70 ms    | ~270 Melem/s       |
+| `two_hop_expand`                    | 100       | ~4.52 ms    | ~22.1 Kelem/s      |
+| `two_hop_expand`                    | 10,000    | ~6.41 ms    | ~1.56 Melem/s      |
+| `two_hop_expand`                    | 1,000,000 | ~6.16 ms    | ~162 Melem/s       |
+
+Numbers are illustrative; your hardware, compiler, and runtime load will affect results.
+
 ## Python Bindings
 
 Python bindings for this crate live under `python/src/graph.rs` and expose the same configuration and query APIs via PyO3.