Passing Messages between Threads

Additional Resources

• Message Passing With Rust MPSC Channels
• Threads, Messaging, and MPSC in Rust

Exercises

Passing message 1

// Fix the code to make it compile and produce the correct output.

use std::sync::mpsc::{self, Sender};
use std::thread;

fn main() {
    let (tx, rx) = mpsc::channel();
    let nums = [12, 43, 54, 43, 53, 52, 98, 89];
    sum(&nums, 3, tx);
    let mut res = 0;
    for sum in rx {
        res += sum;
    }
    println!("Sum of numbers: {res}");
}

// calculate sum of numbers using specified number of threads
fn sum(nums: &[i32], thread_count: usize, tx) {
    let elements_per_thread = nums.len() / thread_count;
    let mut start_pos;
    let mut partition;
    for i in 0..thread_count - 1 {
        start_pos = i * elements_per_thread;
        partition = Vec::from(&nums[start_pos..start_pos + elements_per_thread]);
        let tx_clone = tx.clone();
        thread::spawn(move || {
            let mut sum = 0;
            for num in partition {
                sum += num;
            }
        });
    }
    // sum the remaining elements using last thread
    partition = Vec::from(&nums[(thread_count - 1) * elements_per_thread..]);
    thread::spawn(move || {
        let mut sum = 0;
        for num in partition {
            sum += num;
        }
        tx.send(sum).unwrap()
    });
}

use std::sync::mpsc::{self, Sender};
use std::thread;

fn main() {
  let (tx, rx) = mpsc::channel();
  let nums = [12, 43, 54, 43, 53, 52, 98, 89];
  sum(&nums, 3, tx);
  let mut res = 0;
  for sum in rx {
      res += sum;
  }
  println!("Sum of numbers: {res}");
}

// calculate sum of numbers using specified number of threads
fn sum(nums: &[i32], thread_count: usize, tx: Sender<i32>) {
  let elements_per_thread = nums.len() / thread_count;
  let mut start_pos;
  let mut partition;
  for i in 0..thread_count - 1 {
      start_pos = i * elements_per_thread;
      partition = Vec::from(&nums[start_pos..start_pos + elements_per_thread]);
      let tx_clone = tx.clone();
      thread::spawn(move || {
          let mut sum = 0;
          for num in partition {
              sum += num;
          }
          tx_clone.send(sum).unwrap();
      });
  }
  // sum the remaining elements using last thread
  partition = Vec::from(&nums[(thread_count - 1) * elements_per_thread..]);
  thread::spawn(move || {
      let mut sum = 0;
      for num in partition {
          sum += num;
      }
      tx.send(sum).unwrap()
  });
}

Passing message 2

// Fix the code to make it compile.

use std::sync::mpsc;
use std::thread;

fn main() {
    let sentences = [
        "!tpircs llehs a eb ot detnaw eh esuaceB ?tsuR nrael barC eht sirreF did yhW".to_owned(),
        "!sgel sih fo thgie lla htiw tsuR ni edoc nac eh - reksat-itlum etamitlu eht si barC eht sirreF".to_owned()
    ];
    let (tx, rx) = mpsc::channel();
    for sentence in sentences {
        let tx_clone = tx.clone();
        thread::spawn(|| {
            let reversed = sentence.chars().rev().collect::<String>();
        });
    }
    drop(tx);
    let printer = thread::spawn(|| {
        println!("Reversed sentences:");
        for sentence in rx {
            println!("{sentence}");
        }
    });
    printer.join().unwrap();
}

use std::sync::mpsc;
use std::thread;

fn main() {
  let sentences = [
      "!tpircs llehs a eb ot detnaw eh esuaceB ?tsuR nrael barC eht sirreF did yhW".to_owned(),
      "!sgel sih fo thgie lla htiw tsuR ni edoc nac eh - reksat-itlum etamitlu eht si barC eht sirreF".to_owned()
  ];
  let (tx, rx) = mpsc::channel();
  for sentence in sentences {
      let tx_clone = tx.clone();
      thread::spawn(move || {
          let reversed = sentence.chars().rev().collect::<String>();
          tx_clone.send(reversed).unwrap();
      });
  }
  drop(tx);
  let printer = thread::spawn(|| {
      println!("Reversed sentences:");
      for sentence in rx {
          println!("{sentence}");
      }
  });
  printer.join().unwrap();
}