Add --setup option, closes #8

src/hyperfine/benchmark.rs

@@ -2,7 +2,7 @@ use std::io;
 use std::process::{Command, Stdio};
 use std::time::Instant;
 
-use ansi_term::Colour::{Cyan, Green, White, Yellow, Purple};
+use ansi_term::Colour::{Cyan, Green, Purple, White, Yellow};
 use statistical::{mean, standard_deviation};
 
 use hyperfine::internal::{get_progress_bar, max, min, HyperfineOptions, Second, Warnings,
@@ -133,6 +133,14 @@ pub fn run_benchmark(
     // Set up progress bar (and spinner for initial measurement)
     let bar = get_progress_bar(options.min_runs, "Initial time measurement");
 
+    // Run setup / cleanup command
+    let run_setup_command = || {
+        if let Some(ref setup_command) = options.setup_command {
+            let _ = time_shell_command(setup_command, options.ignore_failure, None);
+        }
+    };
+    run_setup_command();
+
     // Initial timing run
     let res = time_shell_command(cmd, options.ignore_failure, Some(shell_spawning_time))?;
 
@@ -157,6 +165,8 @@ pub fn run_benchmark(
 
     // Gather statistics
     for _ in 0..count_remaining {
+        run_setup_command();
+
         let msg = {
             let mean = format_duration(mean(&execution_times), Unit::Auto);
             format!("Current estimate: {}", Green.paint(mean))

src/hyperfine/internal.rs

@@ -21,6 +21,9 @@ pub struct HyperfineOptions {
 
     /// Whether or not to ignore non-zero exit codes
     pub ignore_failure: bool,
+
+    /// Command to run before each benchmark run
+    pub setup_command: Option<String>,
 }
 
 impl Default for HyperfineOptions {
@@ -30,6 +33,7 @@ impl Default for HyperfineOptions {
             min_runs: 10,
             min_time_sec: 3.0,
             ignore_failure: false,
+            setup_command: None,
         }
     }
 }

src/main.rs

@@ -35,6 +35,9 @@ fn run(commands: &Vec<&str>, options: &HyperfineOptions) -> io::Result<()> {
 }
 
 fn main() {
+    // Process command line options
+    let mut options = HyperfineOptions::default();
+
     let matches = App::new("hyperfine")
         .version(crate_version!())
         .setting(AppSettings::ColoredHelp)
@@ -47,13 +50,33 @@ fn main() {
                 .multiple(true)
                 .empty_values(false),
         )
+        .arg(
+            Arg::with_name("ignore-failure")
+                .long("ignore-failure")
+                .short("i")
+                .help("Ignore non-zero exit codes"),
+        )
+        .arg(
+            Arg::with_name("setup")
+                .long("setup")
+                .short("S")
+                .takes_value(true)
+                .value_name("CMD")
+                .help(
+                    "Execute CMD before each benchmark run. This is useful for \
+                     clearing disk caches, for example.",
+                ),
+        )
         .arg(
             Arg::with_name("warmup")
                 .long("warmup")
                 .short("w")
                 .takes_value(true)
                 .value_name("NUM")
-                .help("Perform NUM warmup runs before the actual benchmark"),
+                .help(
+                    "Perform NUM warmup runs before the actual benchmark. This can be used \
+                     to fill (disk) caches for I/O-heavy programs.",
+                ),
         )
         .arg(
             Arg::with_name("min-runs")
@@ -61,20 +84,18 @@ fn main() {
                 .short("m")
                 .takes_value(true)
                 .value_name("NUM")
-                .help("Perform at least NUM runs for each command"),
+                .help(&format!(
-        )
+                    "Perform at least NUM runs for each command (default: {}).",
-        .arg(
+                    options.min_runs
-            Arg::with_name("ignore-failure")
+                )),
-                .long("ignore-failure")
-                .short("i")
-                .help("Ignore non-zero exit codes"),
         )
         .get_matches();
 
-    let str_to_u64 = |n| u64::from_str_radix(n, 10).ok();
+    options.ignore_failure = matches.is_present("ignore-failure");
 
-    // Process command line options
+    options.setup_command = matches.value_of("setup").map(String::from);
-    let mut options = HyperfineOptions::default();
+
+    let str_to_u64 = |n| u64::from_str_radix(n, 10).ok();
 
     options.warmup_count = matches
         .value_of("warmup")
@@ -86,8 +107,6 @@ fn main() {
         options.min_runs = cmp::max(2, min_runs);
     }
 
-    options.ignore_failure = matches.is_present("ignore-failure");
-
     let commands = matches.values_of("command").unwrap().collect();
     let res = run(&commands, &options);