CODEWITHSUNDEEP
rustwhile-looprayon
JNP
JNP

Reputation: 151

Rust - How to process while loop for vector in parallel with Rayon?

I am trying to process vector with while loop. currently it is sequential taking each element at a time. Is there a way to process vector elements in parallel with rayon and get the same result. Will it increase the performance of the code given below? Basically I am getting continuous messages from tcp client and converting them in to vector and then process them. I want to make processing part faster. sample code is given below.

fn main() {
    let r = process(false);
}

fn process (choice: bool) -> i32 {
    let mut i = 0;
    let my_string = "s1/s2/s3/s4/s5/s6/s7".to_string();
    let my_vector: Vec<&str> = my_string.as_str().split("/").collect();
    let mut tag_path = "MyString".to_string();
    let mut message = "Variable = ".to_string();
    let mut root_path = "".to_string();
    return if !choice {
        while i < my_vector.len() {
            tag_path += "/";
            tag_path += my_vector[i];
            if i != my_vector.len() - 1 {
                message = tag_path.clone();
                let my_target_1 = tag_path.clone() + ":";
                println!("{}", my_target_1)
            } else {
                let my_target_2 = tag_path.clone() + ",";
                println!("{}", my_target_2);
            }
            root_path = message.clone();
            i += 1;
        }
        1
    } else {
        0
    }
}

Upvotes: 0

Views: 1129

Answers (1)

isekaijin
isekaijin

Reputation: 19742

Your code is not slow because you are missing parallelism opportunities, but rather because you are copying ever longer strings in a way that is reminiscent of Shlemiel the Painter's algorithm. Remember that copying strings runs in linear time in the length of the string.

(Kids, this is why basic computer science is so important!)

Since some parts of your snippet are irrelevant to your actual problem (e.g., the choice argument), I have taken the liberty of removing them from my answer. After simplifying your code, what I obtained is this:

fn main() {
    let domain = "example.com";
    let path = "s1/s2/s3/s4/s5/s6/s7";
    let matches = path.match_indices('/');
    
    for (pos, _) in matches {
        println!("{}/{}:", domain, &path[0..pos]);
    }
    
    println!("{}/{},", domain, path)
}

To print a prefix of the full path, you just need to take a slice starting at the beginning of the path (i.e., the 0-th character) and ending just before the corresponding '/' (i.e., the pos-th character). This explains the line in the for loop.

Upvotes: 0

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