CODEWITHSUNDEEP
javascriptnode.jsrust
shane
shane

Reputation: 862

How is Node so much faster in this benchmark?

In an attempt to learn some systems programming, I was going to attempt to write a tokeniser in rust. Immediately though I found it to be extremely slow at iterating over a string's chars. I put together a simple benchmark to show what I mean.

src/bench.html is a html doc with approx 3000 chars

node: 

var input = require('fs').readFileSync('src/bench.html', 'utf8');
var len   = input.length;

for(var i = 0; i < 100; i+=1) run();

function run () {
    var index = 0;
    while (index < len) {
        var c = input.charAt(index);
        // noop
        index++;
    }
}

rust: 

use std::error::Error;
use std::fs::File;
use std::io::prelude::*;
use std::path::Path;

fn main() {
    // Create a path to the desired file
    let path = Path::new("src/bench.html");
    let display = path.display();

    // Open the path in read-only mode, returns `io::Result<File>`
    let mut file = match File::open(&path) {
        // The `description` method of `io::Error` returns a string that
        // describes the error
        Err(why) => panic!("couldn't open {}: {}", display,
                                                   Error::description(&why)),
        Ok(file) => file,
    };

    // Read the file contents into a string, returns `io::Result<usize>`
    let mut s     = String::new();

    match file.read_to_string(&mut s) {
        Err(why) => panic!("couldn't read {}: {}", display,
                                                   Error::description(&why)),
        Ok(_) => {
            for x in 1..100 {
                for token in s.chars() {
                    match token {
                        _ => {
                            // noop
                        }
                    }
                }
            }
            println!("done!");
        }
    }
}

Can someone explain what I'm doing incorrectly in the rust example to make it 10x slower than the same thing in node?

All code can be found here https://github.com/shakyShane/rust-vs-node

Upvotes: 4

Views: 224

Answers (1)

shane
shane

Reputation: 862

Simple answer, when benchmarking, don't use target/debug/program but run cargo build --release first. This will give you target/release/program for your benchmarks :)

Upvotes: 5

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