python - 与 Python 代码相比，我如何提高 Rust 代码的性能？

Question

我如何提高我的 Rust 代码的性能，因为 Python 需要大约 5 秒才能完成，而 Rust 需要 7 秒。

我正在使用 build --release

Rust 代码

fn main() {
    let mut n = 0;

    loop {
        n += 1;
        println!("The value of n is {}", &n);
        if n == 100000 {
            break;
        }
    }
}

Python3代码

n = 0
while True:
   n+=1
   print("The value of n is ",n)
   if n == 100000:
       break

Answer 1

如果我没记错的话，println 锁定标准输出。取自Rust Performance Pitfalls :

[...] the default print! macros will lock STDOUT for each write operation. So if you have a larger textual output (or input from STDIN), you should lock manually.

This:

let mut out = File::new("test.out");
println!("{}", header);
for line in lines {
    println!("{}", line);
    writeln!(out, "{}", line);
}
println!("{}", footer);

locks and unlocks io::stdout a lot, and does a linear number of (potentially small) writes both to stdout and the file. Speed it up with:

{
    let mut out = File::new("test.out");
    let mut buf = BufWriter::new(out);
    let mut lock = io::stdout().lock();
    writeln!(lock, "{}", header);
    for line in lines {
        writeln!(lock, "{}", line);
        writeln!(buf, "{}", line);
    }
    writeln!(lock, "{}", footer);
}   // end scope to unlock stdout and flush/close buf> 

This locks only once and writes only once the buffer is filled (or buf is closed), so it should be much faster.

Similarly, for network IO, you may want to use buffered IO.