fix: divan walltime metric

Author: not-matthias

crates/codspeed/src/walltime.rs

@@ -50,6 +50,16 @@ impl RawWallTimeData {
 /// Entry point called in patched integration to harvest raw walltime data
 ///
 /// `CODSPEED_CARGO_WORKSPACE_ROOT` is expected to be set for this to work
+///
+/// # Arguments
+///
+/// - `scope`: The used integration, e.g. "divan" or "criterion"
+/// - `name`: The name of the benchmark
+/// - `uri`: The URI of the benchmark
+/// - `iter_per_round`: The number of iterations per round for the benchmark (=sample_size)
+/// - `max_time_ns`: The time limit for the benchmark in nanoseconds (if defined)
+/// - `times_ns`: The **average** time per iteration in nanoseconds. Calculated as `total_time_ns / iter_per_round`
+///
 pub fn collect_raw_walltime_results(
     scope: &str,
     name: String,

crates/divan_compat/Cargo.toml

@@ -25,3 +25,7 @@ codspeed-divan-compat-macros = { version = "=2.10.1", path = './macros' }
 [[bench]]
 name = "basic_example"
 harness = false
+
+[[bench]]
+name = "sleep_benches"
+harness = false

crates/divan_compat/benches/sleep_benches.rs

@@ -0,0 +1,29 @@
+#[divan::bench]
+fn sleep_1ms() {
+    std::thread::sleep(std::time::Duration::from_millis(1));
+}
+
+#[divan::bench]
+fn sleep_10ms() {
+    std::thread::sleep(std::time::Duration::from_millis(10));
+}
+
+#[divan::bench]
+fn sleep_50ms() {
+    std::thread::sleep(std::time::Duration::from_millis(50));
+}
+
+#[divan::bench]
+fn sleep_100ms() {
+    std::thread::sleep(std::time::Duration::from_millis(100));
+}
+
+// Tests COD-1044, do not modify the sample size or count!
+#[divan::bench(sample_size = 3, sample_count = 6)]
+fn sleep_100ms_with_custom_sample() {
+    std::thread::sleep(std::time::Duration::from_millis(100));
+}
+
+fn main() {
+    codspeed_divan_compat::main();
+}

crates/divan_compat/divan_fork/src/divan.rs

@@ -424,8 +424,13 @@ mod codspeed {
         };
 
         let iter_per_round = bench_context.samples.sample_size;
+
+        // Note: times_ns = total time of the round execution, but we need the time per iteration.
+        // See: BenchContext::compute_stats in bench/mod.rs
         let times_ns: Vec<_> =
             bench_context.samples.time_samples.iter().map(|s| s.duration.picos / 1_000).collect();
+        let avg_times_ns: Vec<_> = times_ns.iter().map(|&t| t / iter_per_round as u128).collect();
+
         let max_time_ns = bench_context.options.max_time.map(|t| t.as_nanos());
 
         if let Err(error) = ::codspeed::fifo::send_cmd(codspeed::fifo::Command::CurrentBenchmark {
@@ -443,7 +448,7 @@ mod codspeed {
             uri,
             iter_per_round,
             max_time_ns,
-            times_ns,
+            avg_times_ns,
         );
     }
 }