Fetch network graph cache and run benchmarks on CI

Author: TheBlueMatt

.github/workflows/build.yml

@@ -126,6 +126,39 @@ jobs:
           token: f421b687-4dc2-4387-ac3d-dc3b2528af57
           fail_ci_if_error: true
 
+  benchmark:
+    runs-on: ubuntu-latest
+    env:
+      TOOLCHAIN: nightly
+    steps:
+      - name: Checkout source code
+        uses: actions/checkout@v2
+      - name: Install Rust ${{ env.TOOLCHAIN }} toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ env.TOOLCHAIN }}
+          override: true
+          profile: minimal
+      - name: Cache routing graph snapshot
+        id: cache-graph
+        uses: actions/cache@v2
+        with:
+          path: lightning/net_graph-2021-02-12.bin
+          key: net_graph-2021-02-12
+      - name: Fetch routing graph snapshot
+        if: steps.cache-graph.outputs.cache-hit != 'true'
+        run: |
+          wget -O lightning/net_graph-2021-02-12.bin https://bitcoin.ninja/ldk-net_graph-879e309c128-2020-02-12.bin
+          if [ "$(sha256sum lightning/net_graph-2021-02-12.bin | awk '{ print $1 }')" != "890a1f80dfb6ef674a1e4ff0f23cd73d740731c395f99d85abbede0cfbb701ab" ]; then
+            echo "Bad hash"
+            exit 1
+          fi
+      - name: Run benchmarks on Rust ${{ matrix.toolchain }}
+        run: |
+          cd lightning
+          cargo bench --features unstable
+          cd ..
+
   check_commits:
     runs-on: ubuntu-latest
     env:

lightning/src/routing/router.rs

@@ -1295,16 +1295,31 @@ mod benches {
 
 	#[bench]
 	fn generate_routes(bench: &mut Bencher) {
-		let mut seed: usize = 0xdeadbeef;
 		let mut d = File::open("net_graph-2021-02-12.bin").expect("Please fetch https://bitcoin.ninja/ldk-net_graph-879e309c128-2020-02-12.bin and place it at lightning/net_graph-2021-02-12.bin");
 		let graph = NetworkGraph::read(&mut d).unwrap();
-		let node_count = graph.get_nodes().len();
+
+		// First, get 100 (source, destination) pairs for which route-getting actually succeeds...
+		let mut path_endpoints = Vec::new();
+		let mut seed: usize = 0xdeadbeef;
+		'load_endpoints: for _ in 0..100 {
+			loop {
+				seed *= 0xdeadbeef;
+				let src = graph.get_nodes().keys().skip(seed % graph.get_nodes().len()).next().unwrap();
+				seed *= 0xdeadbeef;
+				let dst = graph.get_nodes().keys().skip(seed % graph.get_nodes().len()).next().unwrap();
+				if get_route(src, &graph, dst, None, &[], seed as u64 % 1_000_000, 42, &DummyLogger{}).is_ok() {
+					path_endpoints.push((src, dst));
+					continue 'load_endpoints;
+				}
+			}
+		}
+
+		// ...then benchmark finding paths between the nodes we learned.
+		let mut idx = 0;
 		bench.iter(|| {
-			seed *= 0xdeadbeef;
-			let src = graph.get_nodes().keys().skip(seed % node_count).next().unwrap();
-			seed *= 0xdeadbeef;
-			let dst = graph.get_nodes().keys().skip(seed % node_count).next().unwrap();
-			let _ = get_route(src, &graph, dst, None, &[], seed as u64 % 1_000_000, 42, &DummyLogger{});
+			let (src, dst) = path_endpoints[idx % path_endpoints.len()];
+			assert!(get_route(src, &graph, dst, None, &[], seed as u64 % 1_000_000, 42, &DummyLogger{}).is_ok());
+			idx += 1;
 		});
 	}
 }