bench mycelium round trips

2 files changed, 35 insertions, 2 deletions

diff --git a/docs/development.md b/docs/development.md
index 1771539..2ed15f6 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -21,8 +21,9 @@ The benchmarks are ignored tests named `bench_*`: the document's (writes and syn
 messages, `document/bench.rs`), the remakes' replay (`remake/bench.rs`), and what
 passing changes on costs over the simulated network (`simtest/bench.rs`: messages and
 bytes per write by kind, propagation delays, for a full mesh, a writer behind NAT, two
-transports, partial meshes of 50 and 100 nodes, lossy links, a member away for a
-while, and members joining during the writes; several minutes, or one scenario alone
+transports, partial meshes of 50 and 100 nodes, lossy links (with delays at random,
+and with Mycelium's round trips, each link its own), a member away for a while, and
+members joining during the writes; several minutes, or one scenario alone
 with `BENCH_SCENARIO`, part of its name: `BENCH_SCENARIO=NAT`; all at once with
 `BENCH_PARALLEL=1`, faster on many cores, though sharing them makes delays come out
 somewhat higher; and in `bench_bridge`, large values from a writer on a fast transport
diff --git a/src/simtest/bench.rs b/src/simtest/bench.rs
index d5ca624..06b557e 100644
--- a/src/simtest/bench.rs
+++ b/src/simtest/bench.rs
@@ -105,6 +105,28 @@ fn lossy(sim: &Sim, _: &[String]) {
     });
 }
 
+/// As `lossy`, but each link with a latency of its own, as over Mycelium: round trips
+/// from 20 to 250 ms, each message within a fifth of its link's. So what the uniform
+/// 50–500 ms of `lossy` gives that real links don't: messages on one link overtake each
+/// other only within the jitter, and the fast links to a node are fast every time.
+fn mycelium_like(sim: &Sim, ids: &[String]) {
+    let mut rng = crate::testrand::Rng::new(7);
+    for (i, from) in ids.iter().enumerate() {
+        for to in &ids[i + 1..] {
+            let rtt_ms = 20.0 + rng.next_f64() * 230.0;
+            let half = Duration::from_secs_f64(rtt_ms / 2.0 / 1000.0);
+            let link = LinkParams {
+                loss: 0.02,
+                duplicate: 0.01,
+                delay: (half * 4 / 5, half * 6 / 5),
+                ..LinkParams::default()
+            };
+            sim.net.set_link(from, to, link.clone());
+            sim.net.set_link(to, from, link);
+        }
+    }
+}
+
 const SCENARIOS: &[Scenario] = &[
     Scenario {
         name: "full mesh, 13 nodes",
@@ -178,6 +200,16 @@ const SCENARIOS: &[Scenario] = &[
         away: None,
         joining: 5,
     },
+    // Last, so the others keep their seeds.
+    Scenario {
+        name: "partial mesh, lossy links with Mycelium's round trips, 50 nodes",
+        nodes: 50,
+        on: sim_only,
+        net: mycelium_like,
+        writer: 1,
+        away: None,
+        joining: 0,
+    },
 ];
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 16)]