1 //! Benchmarking module.
5 test_result::TestResult,
6 types::{TestDesc, TestId},
13 use std::panic::{catch_unwind, AssertUnwindSafe};
14 use std::sync::{Arc, Mutex};
15 use std::time::{Duration, Instant};
17 /// An identity function that *__hints__* to the compiler to be maximally pessimistic about what
18 /// `black_box` could do.
20 /// See [`std::hint::black_box`] for details.
22 pub fn black_box<T>(dummy: T) -> T {
23 std::hint::black_box(dummy)
26 /// Manager of the benchmarking runs.
28 /// This is fed into functions marked with `#[bench]` to allow for
29 /// set-up & tear-down before running a piece of code repeatedly via a
34 summary: Option<stats::Summary>,
39 /// Callback for benchmark functions to run in their body.
40 pub fn iter<T, F>(&mut self, mut inner: F)
44 if self.mode == BenchMode::Single {
45 ns_iter_inner(&mut inner, 1);
49 self.summary = Some(iter(&mut inner));
52 pub fn bench<F>(&mut self, mut f: F) -> Option<stats::Summary>
54 F: FnMut(&mut Bencher),
61 #[derive(Debug, Clone, PartialEq)]
62 pub struct BenchSamples {
63 pub ns_iter_summ: stats::Summary,
67 pub fn fmt_bench_samples(bs: &BenchSamples) -> String {
69 let mut output = String::new();
71 let median = bs.ns_iter_summ.median as usize;
72 let deviation = (bs.ns_iter_summ.max - bs.ns_iter_summ.min) as usize;
76 "{:>11} ns/iter (+/- {})",
77 fmt_thousands_sep(median, ','),
78 fmt_thousands_sep(deviation, ',')
82 write!(output, " = {} MB/s", bs.mb_s).unwrap();
87 // Format a number with thousands separators
88 fn fmt_thousands_sep(mut n: usize, sep: char) -> String {
90 let mut output = String::new();
91 let mut trailing = false;
92 for &pow in &[9, 6, 3, 0] {
93 let base = 10_usize.pow(pow);
94 if pow == 0 || trailing || n / base != 0 {
96 write!(output, "{}", n / base).unwrap();
98 write!(output, "{:03}", n / base).unwrap();
111 fn ns_iter_inner<T, F>(inner: &mut F, k: u64) -> u64
115 let start = Instant::now();
119 start.elapsed().as_nanos() as u64
122 pub fn iter<T, F>(inner: &mut F) -> stats::Summary
126 // Initial bench run to get ballpark figure.
127 let ns_single = ns_iter_inner(inner, 1);
129 // Try to estimate iter count for 1ms falling back to 1m
130 // iterations if first run took < 1ns.
131 let ns_target_total = 1_000_000; // 1ms
132 let mut n = ns_target_total / cmp::max(1, ns_single);
134 // if the first run took more than 1ms we don't want to just
135 // be left doing 0 iterations on every loop. The unfortunate
136 // side effect of not being able to do as many runs is
137 // automatically handled by the statistical analysis below
138 // (i.e., larger error bars).
141 let mut total_run = Duration::new(0, 0);
142 let samples: &mut [f64] = &mut [0.0_f64; 50];
144 let loop_start = Instant::now();
146 for p in &mut *samples {
147 *p = ns_iter_inner(inner, n) as f64 / n as f64;
150 stats::winsorize(samples, 5.0);
151 let summ = stats::Summary::new(samples);
153 for p in &mut *samples {
154 let ns = ns_iter_inner(inner, 5 * n);
155 *p = ns as f64 / (5 * n) as f64;
158 stats::winsorize(samples, 5.0);
159 let summ5 = stats::Summary::new(samples);
161 let loop_run = loop_start.elapsed();
163 // If we've run for 100ms and seem to have converged to a
165 if loop_run > Duration::from_millis(100)
166 && summ.median_abs_dev_pct < 1.0
167 && summ.median - summ5.median < summ5.median_abs_dev
172 total_run += loop_run;
173 // Longest we ever run for is 3s.
174 if total_run > Duration::from_secs(3) {
178 // If we overflow here just return the results so far. We check a
179 // multiplier of 10 because we're about to multiply by 2 and the
180 // next iteration of the loop will also multiply by 5 (to calculate
182 n = match n.checked_mul(10) {
194 monitor_ch: Sender<CompletedTest>,
198 F: FnMut(&mut Bencher),
200 let mut bs = Bencher { mode: BenchMode::Auto, summary: None, bytes: 0 };
202 let data = Arc::new(Mutex::new(Vec::new()));
205 io::set_output_capture(Some(data.clone()));
208 let result = catch_unwind(AssertUnwindSafe(|| bs.bench(f)));
210 io::set_output_capture(None);
212 let test_result = match result {
214 Ok(Some(ns_iter_summ)) => {
215 let ns_iter = cmp::max(ns_iter_summ.median as u64, 1);
216 let mb_s = bs.bytes * 1000 / ns_iter;
218 let bs = BenchSamples { ns_iter_summ, mb_s: mb_s as usize };
219 TestResult::TrBench(bs)
222 // iter not called, so no data.
223 // FIXME: error in this case?
224 let samples: &mut [f64] = &mut [0.0_f64; 1];
225 let bs = BenchSamples { ns_iter_summ: stats::Summary::new(samples), mb_s: 0 };
226 TestResult::TrBench(bs)
228 Err(_) => TestResult::TrFailed,
231 let stdout = data.lock().unwrap().to_vec();
232 let message = CompletedTest::new(id, desc, test_result, None, stdout);
233 monitor_ch.send(message).unwrap();
236 pub fn run_once<F>(f: F)
238 F: FnMut(&mut Bencher),
240 let mut bs = Bencher { mode: BenchMode::Single, summary: None, bytes: 0 };