1 files changed, 242 insertions, 0 deletions
diff --git a/library/test/src/bench.rs b/library/test/src/bench.rs
new file mode 100644
index 000000000..7869ba2c0
--- /dev/null
+++ b/library/test/src/bench.rs
@@ -0,0 +1,242 @@
+//! Benchmarking module.
+use super::{
+    event::CompletedTest,
+    options::BenchMode,
+    test_result::TestResult,
+    types::{TestDesc, TestId},
+    Sender,
+};
+
+use crate::stats;
+use std::cmp;
+use std::io;
+use std::panic::{catch_unwind, AssertUnwindSafe};
+use std::sync::{Arc, Mutex};
+use std::time::{Duration, Instant};
+
+/// An identity function that *__hints__* to the compiler to be maximally pessimistic about what
+/// `black_box` could do.
+///
+/// See [`std::hint::black_box`] for details.
+#[inline(always)]
+pub fn black_box<T>(dummy: T) -> T {
+    std::hint::black_box(dummy)
+}
+
+/// Manager of the benchmarking runs.
+///
+/// This is fed into functions marked with `#[bench]` to allow for
+/// set-up & tear-down before running a piece of code repeatedly via a
+/// call to `iter`.
+#[derive(Clone)]
+pub struct Bencher {
+    mode: BenchMode,
+    summary: Option<stats::Summary>,
+    pub bytes: u64,
+}
+
+impl Bencher {
+    /// Callback for benchmark functions to run in their body.
+    pub fn iter<T, F>(&mut self, mut inner: F)
+    where
+        F: FnMut() -> T,
+    {
+        if self.mode == BenchMode::Single {
+            ns_iter_inner(&mut inner, 1);
+            return;
+        }
+
+        self.summary = Some(iter(&mut inner));
+    }
+
+    pub fn bench<F>(&mut self, mut f: F) -> Option<stats::Summary>
+    where
+        F: FnMut(&mut Bencher),
+    {
+        f(self);
+        self.summary
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct BenchSamples {
+    pub ns_iter_summ: stats::Summary,
+    pub mb_s: usize,
+}
+
+pub fn fmt_bench_samples(bs: &BenchSamples) -> String {
+    use std::fmt::Write;
+    let mut output = String::new();
+
+    let median = bs.ns_iter_summ.median as usize;
+    let deviation = (bs.ns_iter_summ.max - bs.ns_iter_summ.min) as usize;
+
+    write!(
+        output,
+        "{:>11} ns/iter (+/- {})",
+        fmt_thousands_sep(median, ','),
+        fmt_thousands_sep(deviation, ',')
+    )
+    .unwrap();
+    if bs.mb_s != 0 {
+        write!(output, " = {} MB/s", bs.mb_s).unwrap();
+    }
+    output
+}
+
+// Format a number with thousands separators
+fn fmt_thousands_sep(mut n: usize, sep: char) -> String {
+    use std::fmt::Write;
+    let mut output = String::new();
+    let mut trailing = false;
+    for &pow in &[9, 6, 3, 0] {
+        let base = 10_usize.pow(pow);
+        if pow == 0 || trailing || n / base != 0 {
+            if !trailing {
+                write!(output, "{}", n / base).unwrap();
+            } else {
+                write!(output, "{:03}", n / base).unwrap();
+            }
+            if pow != 0 {
+                output.push(sep);
+            }
+            trailing = true;
+        }
+        n %= base;
+    }
+
+    output
+}
+
+fn ns_iter_inner<T, F>(inner: &mut F, k: u64) -> u64
+where
+    F: FnMut() -> T,
+{
+    let start = Instant::now();
+    for _ in 0..k {
+        black_box(inner());
+    }
+    start.elapsed().as_nanos() as u64
+}
+
+pub fn iter<T, F>(inner: &mut F) -> stats::Summary
+where
+    F: FnMut() -> T,
+{
+    // Initial bench run to get ballpark figure.
+    let ns_single = ns_iter_inner(inner, 1);
+
+    // Try to estimate iter count for 1ms falling back to 1m
+    // iterations if first run took < 1ns.
+    let ns_target_total = 1_000_000; // 1ms
+    let mut n = ns_target_total / cmp::max(1, ns_single);
+
+    // if the first run took more than 1ms we don't want to just
+    // be left doing 0 iterations on every loop. The unfortunate
+    // side effect of not being able to do as many runs is
+    // automatically handled by the statistical analysis below
+    // (i.e., larger error bars).
+    n = cmp::max(1, n);
+
+    let mut total_run = Duration::new(0, 0);
+    let samples: &mut [f64] = &mut [0.0_f64; 50];
+    loop {
+        let loop_start = Instant::now();
+
+        for p in &mut *samples {
+            *p = ns_iter_inner(inner, n) as f64 / n as f64;
+        }
+
+        stats::winsorize(samples, 5.0);
+        let summ = stats::Summary::new(samples);
+
+        for p in &mut *samples {
+            let ns = ns_iter_inner(inner, 5 * n);
+            *p = ns as f64 / (5 * n) as f64;
+        }
+
+        stats::winsorize(samples, 5.0);
+        let summ5 = stats::Summary::new(samples);
+
+        let loop_run = loop_start.elapsed();
+
+        // If we've run for 100ms and seem to have converged to a
+        // stable median.
+        if loop_run > Duration::from_millis(100)
+            && summ.median_abs_dev_pct < 1.0
+            && summ.median - summ5.median < summ5.median_abs_dev
+        {
+            return summ5;
+        }
+
+        total_run += loop_run;
+        // Longest we ever run for is 3s.
+        if total_run > Duration::from_secs(3) {
+            return summ5;
+        }
+
+        // If we overflow here just return the results so far. We check a
+        // multiplier of 10 because we're about to multiply by 2 and the
+        // next iteration of the loop will also multiply by 5 (to calculate
+        // the summ5 result)
+        n = match n.checked_mul(10) {
+            Some(_) => n * 2,
+            None => {
+                return summ5;
+            }
+        };
+    }
+}
+
+pub fn benchmark<F>(
+    id: TestId,
+    desc: TestDesc,
+    monitor_ch: Sender<CompletedTest>,
+    nocapture: bool,
+    f: F,
+) where
+    F: FnMut(&mut Bencher),
+{
+    let mut bs = Bencher { mode: BenchMode::Auto, summary: None, bytes: 0 };
+
+    let data = Arc::new(Mutex::new(Vec::new()));
+
+    if !nocapture {
+        io::set_output_capture(Some(data.clone()));
+    }
+
+    let result = catch_unwind(AssertUnwindSafe(|| bs.bench(f)));
+
+    io::set_output_capture(None);
+
+    let test_result = match result {
+        //bs.bench(f) {
+        Ok(Some(ns_iter_summ)) => {
+            let ns_iter = cmp::max(ns_iter_summ.median as u64, 1);
+            let mb_s = bs.bytes * 1000 / ns_iter;
+
+            let bs = BenchSamples { ns_iter_summ, mb_s: mb_s as usize };
+            TestResult::TrBench(bs)
+        }
+        Ok(None) => {
+            // iter not called, so no data.
+            // FIXME: error in this case?
+            let samples: &mut [f64] = &mut [0.0_f64; 1];
+            let bs = BenchSamples { ns_iter_summ: stats::Summary::new(samples), mb_s: 0 };
+            TestResult::TrBench(bs)
+        }
+        Err(_) => TestResult::TrFailed,
+    };
+
+    let stdout = data.lock().unwrap().to_vec();
+    let message = CompletedTest::new(id, desc, test_result, None, stdout);
+    monitor_ch.send(message).unwrap();
+}
+
+pub fn run_once<F>(f: F)
+where
+    F: FnMut(&mut Bencher),
+{
+    let mut bs = Bencher { mode: BenchMode::Single, summary: None, bytes: 0 };
+    bs.bench(f);
+}