56 lines
1.9 KiB
Rust
56 lines
1.9 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test performance of a task "spawn ladder", in which children task have
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// many ancestor taskgroups, but with only a few such groups alive at a time.
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// Each child task has to enlist as a descendant in each of its ancestor
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// groups, but that shouldn't have to happen for already-dead groups.
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//
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// The filename is a song reference; google it in quotes.
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// ignore-pretty very bad with line comments
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use std::sync::mpsc::{channel, Sender};
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use std::env;
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use std::thread;
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fn child_generation(gens_left: usize, tx: Sender<()>) {
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// This used to be O(n^2) in the number of generations that ever existed.
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// With this code, only as many generations are alive at a time as tasks
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// alive at a time,
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thread::spawn(move|| {
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if gens_left & 1 == 1 {
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thread::yield_now(); // shake things up a bit
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}
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if gens_left > 0 {
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child_generation(gens_left - 1, tx); // recurse
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} else {
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tx.send(()).unwrap()
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}
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});
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}
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fn main() {
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let args = env::args();
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let args = if env::var_os("RUST_BENCH").is_some() {
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vec!("".to_string(), "100000".to_string())
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} else if args.len() <= 1 {
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vec!("".to_string(), "100".to_string())
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} else {
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args.collect()
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};
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let (tx, rx) = channel();
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child_generation(args[1].parse().unwrap(), tx);
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if rx.recv().is_err() {
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panic!("it happened when we slumbered");
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}
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}
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