Concurrent computing

From Rosetta Code
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Task
Concurrent computing
You are encouraged to solve this task according to the task description, using any language you may know.
Task

Using either native language concurrency syntax or freely available libraries, write a program to display the strings "Enjoy" "Rosetta" "Code", one string per line, in random order.

Concurrency syntax must use threads, tasks, co-routines, or whatever concurrency is called in your language.

Ada[edit]

with Ada.Text_IO, Ada.Numerics.Float_Random;

procedure Concurrent_Hello is
   type Messages is (Enjoy, Rosetta, Code);
   task type Writer (Message : Messages);
   task body Writer is
      Seed : Ada.Numerics.Float_Random.Generator;
   begin
      Ada.Numerics.Float_Random.Reset (Seed); -- time-dependent, see ARM A.5.2
      delay Duration (Ada.Numerics.Float_Random.Random (Seed));
      Ada.Text_IO.Put_Line (Messages'Image(Message));
   end Writer;
   Taks: array(Messages) of access Writer -- 3 Writer tasks will immediately run
     := (new Writer(Enjoy), new Writer(Rosetta), new Writer(Code));
begin
   null; -- the "environment task" doesn't need to do anything
end Concurrent_Hello;

Note that random generator object is local to each task. It cannot be accessed concurrently without mutual exclusion. In order to get different initial states of local generators Reset is called (see ARM A.5.2).

ALGOL 68[edit]

main:(
  PROC echo = (STRING string)VOID:
      printf(($gl$,string));
  PAR(
    echo("Enjoy"),
    echo("Rosetta"),
    echo("Code")
  )
)

APL[edit]

Works with: Dyalog APL

Dyalog APL supports the & operator, which runs a function on its own thread.

{}'Enjoy' 'Rosetta' 'Code'
Output:

(Example)

Enjoy
Code
Rosetta

Astro[edit]

let words = ["Enjoy", "Rosetta", "Code"]

for word in words:
    (word) |> async (w) =>
        sleep(random())
        print(w)

BaCon[edit]

Library: gomp
Works with: OpenMP

BaCon is a BASIC-to-C compiler. Assuming GCC compiler in this demonstration. Based on the C OpenMP source.

' Concurrent computing using the OpenMP extension in GCC. Requires BaCon 3.6 or higher.

' Specify compiler flag
PRAGMA OPTIONS -fopenmp

' Sepcify linker flag
PRAGMA LDFLAGS -lgomp

' Declare array with text
DECLARE str$[] = { "Enjoy", "Rosetta", "Code" }

' Indicate MP optimization for FOR loop
PRAGMA omp parallel for num_threads(3)

' The actual FOR loop
FOR i = 0 TO 2
    PRINT str$[i]
NEXT
Output:
prompt$ bacon concurrent-computing
Converting 'concurrent-computing.bac'... done, 11 lines were processed in 0.002 seconds.
Compiling 'concurrent-computing.bac'... cc  -fopenmp -c concurrent-computing.bac.c
cc -o concurrent-computing concurrent-computing.bac.o -lbacon -lm  -lgomp
Done, program 'concurrent-computing' ready.
prompt$ ./concurrent-computing
Code
Enjoy
Rosetta

BBC BASIC[edit]

The BBC BASIC interpreter is single-threaded so the only way of achieving 'concurrency' (short of using assembler code) is to use timer events:

      INSTALL @lib$+"TIMERLIB"
      
      tID1% = FN_ontimer(100, PROCtask1, 1)
      tID2% = FN_ontimer(100, PROCtask2, 1)
      tID3% = FN_ontimer(100, PROCtask3, 1)
      
      ON ERROR PRINT REPORT$ : PROCcleanup : END
      ON CLOSE PROCcleanup : QUIT
      
      REPEAT
        WAIT 0
      UNTIL FALSE
      END
      
      DEF PROCtask1
      PRINT "Enjoy"
      ENDPROC
      
      DEF PROCtask2
      PRINT "Rosetta"
      ENDPROC
      
      DEF PROCtask3
      PRINT "Code"
      ENDPROC
      
      DEF PROCcleanup
      PROC_killtimer(tID1%)
      PROC_killtimer(tID2%)
      PROC_killtimer(tID3%)
      ENDPROC

C[edit]

Works with: POSIX
Library: pthread
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>

pthread_mutex_t condm = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
int bang = 0;

#define WAITBANG() do { \
   pthread_mutex_lock(&condm); \
   while( bang == 0 ) \
   { \
      pthread_cond_wait(&cond, &condm); \
   } \
   pthread_mutex_unlock(&condm); } while(0);\

void *t_enjoy(void *p)
{
  WAITBANG();
  printf("Enjoy\n");
  pthread_exit(0);
}

void *t_rosetta(void *p)
{
  WAITBANG();
  printf("Rosetta\n");
  pthread_exit(0);
}

void *t_code(void *p)
{
  WAITBANG();
  printf("Code\n");
  pthread_exit(0);
}

typedef void *(*threadfunc)(void *);
int main()
{
   int i;
   pthread_t a[3];
   threadfunc p[3] = {t_enjoy, t_rosetta, t_code};
   
   for(i=0;i<3;i++)
   {
     pthread_create(&a[i], NULL, p[i], NULL);
   }
   sleep(1);
   bang = 1;
   pthread_cond_broadcast(&cond);
   for(i=0;i<3;i++)
   {
     pthread_join(a[i], NULL);
   }
}

Note: since threads are created one after another, it is likely that the execution of their code follows the order of creation. To make this less evident, I've added the bang idea using condition: the thread really executes their code once the gun bang is heard. Nonetheless, I still obtain the same order of creation (Enjoy, Rosetta, Code), and maybe it is because of the order locks are acquired. The only way to obtain randomness seems to be to add random wait in each thread (or wait for special cpu load condition)

OpenMP[edit]

Compile with gcc -std=c99 -fopenmp:

#include <stdio.h>
#include <omp.h>

int main()
{
	const char *str[] = { "Enjoy", "Rosetta", "Code" };
	#pragma omp parallel for num_threads(3)
	for (int i = 0; i < 3; i++)
		printf("%s\n", str[i]);
	return 0;
}

C#[edit]

With Threads[edit]

static Random tRand = new Random();

static void Main(string[] args)
{
	Thread t = new Thread(new ParameterizedThreadStart(WriteText));
	t.Start("Enjoy");

	t = new Thread(new ParameterizedThreadStart(WriteText));
	t.Start("Rosetta");

	t = new Thread(new ParameterizedThreadStart(WriteText));
	t.Start("Code");

	Console.ReadLine();
}

private static void WriteText(object p)
{
	Thread.Sleep(tRand.Next(1000, 4000));
	Console.WriteLine(p);
}

An example result:

Enjoy
Code
Rosetta

With Tasks[edit]

Works with: C sharp version 7.1
using System;
using System.Threading.Tasks;

public class Program
{
    static async Task Main() {
        Task t1 = Task.Run(() => Console.WriteLine("Enjoy"));
        Task t2 = Task.Run(() => Console.WriteLine("Rosetta"));
        Task t3 = Task.Run(() => Console.WriteLine("Code"));

        await Task.WhenAll(t1, t2, t3);
    }
}

With a parallel loop[edit]

using System;
using System.Threading.Tasks;

public class Program
{
    static void Main() => Parallel.ForEach(new[] {"Enjoy", "Rosetta", "Code"}, s => Console.WriteLine(s));
}

C++[edit]

Works with: C++11

The following example compiles with GCC 4.7.

g++ -std=c++11 -D_GLIBCXX_USE_NANOSLEEP -o concomp concomp.cpp

#include <thread>
#include <iostream>
#include <vector>
#include <random>
#include <chrono> 

int main()
{
  std::random_device rd;
  std::mt19937 eng(rd()); // mt19937 generator with a hardware random seed.
  std::uniform_int_distribution<> dist(1,1000);
  std::vector<std::thread> threads;

  for(const auto& str: {"Enjoy\n", "Rosetta\n", "Code\n"}) {
    // between 1 and 1000ms per our distribution
    std::chrono::milliseconds duration(dist(eng)); 

    threads.emplace_back([str, duration](){                                                                    
      std::this_thread::sleep_for(duration);
      std::cout << str;
    });
  }

  for(auto& t: threads) t.join(); 

  return 0;
}

Output:

Enjoy
Code
Rosetta
#include <iostream>
#include <ppl.h> // MSVC++

void a(void) { std::cout << "Eat\n";   }
void b(void) { std::cout << "At\n";    }
void c(void) { std::cout << "Joe's\n"; }

int main()
{
    // function pointers
    Concurrency::parallel_invoke(&a, &b, &c);

    // C++11 lambda functions
    Concurrency::parallel_invoke(
        []{ std::cout << "Enjoy\n";   },
        []{ std::cout << "Rosetta\n"; },
        []{ std::cout << "Code\n";    }
    );
    return 0;
}

Output:

Joe's
Eat
At
Enjoy
Code
Rosetta

Cind[edit]

execute() {
    {# host.println("Enjoy");
     # host.println("Rosetta");
     # host.println("Code"); }
}

Clojure[edit]

A simple way to obtain concurrency is using the future function, which evaluates its body on a separate thread.

(doseq [text ["Enjoy" "Rosetta" "Code"]] 
  (future (println text)))

Using the new (2013) core.async library, "go blocks" can execute asynchronously, sharing threads from a pool. This works even in ClojureScript (the JavaScript target of Clojure) on a single thread. The timeout call is there just to shuffle things up: note this delay doesn't block a thread.

(require '[clojure.core.async :refer [go <! timeout]])
(doseq [text ["Enjoy" "Rosetta" "Code"]]
  (go
    (<! (timeout (rand-int 1000))) ; wait a random fraction of a second,
    (println text)))

CoffeeScript[edit]

Using Bash (or an equivalent shell)[edit]

Works with: Node.js
Works with: Bash

JavaScript, which CoffeeScript compiles to, is single-threaded. This approach launches multiple process to achieve concurrency on Node.js:

{ exec } = require 'child_process'

for word in [ 'Enjoy', 'Rosetta', 'Code' ]
    exec "echo #{word}", (err, stdout) ->
        console.log stdout

Using Node.js[edit]

Works with: Node.js

As stated above, CoffeeScript is single-threaded. This approach launches multiple Node.js processes to achieve concurrency.

# The "master" file.

{ fork } = require 'child_process'
path = require 'path'
child_name = path.join __dirname, 'child.coffee'
words = [ 'Enjoy', 'Rosetta', 'Code' ]

fork child_name, [ word ] for word in words
# child.coffee

console.log process.argv[ 2 ]

Common Lisp[edit]

Concurrency and threads are not part of the Common Lisp standard. However, most implementations provide some interface for concurrency. Bordeaux Threads, used here, provides a compatibility layer for many implementations. (Binding out to *standard-output* before threads are created is needed as each thread gets its own binding for *standard-output*.)

(defun concurrency-example (&optional (out *standard-output*))
  (let ((lock (bordeaux-threads:make-lock)))
    (flet ((writer (string)
             #'(lambda () 
                 (bordeaux-threads:acquire-lock lock t)
                 (write-line string out)
                 (bordeaux-threads:release-lock lock))))
      (bordeaux-threads:make-thread (writer "Enjoy"))
      (bordeaux-threads:make-thread (writer "Rosetta"))
      (bordeaux-threads:make-thread (writer "Code")))))

Crystal[edit]

Crystal requires the use of channels to ensure that the main fiber doesn't exit before any of the new fibers are done, since each fiber sleeping could return control to the main fiber.

require "channel"
require "fiber"
require "random"

done = Channel(Nil).new

"Enjoy Rosetta Code".split.map do |x|
  spawn do
    sleep Random.new.rand(0..500).milliseconds
    puts x
    done.send nil
  end
end

3.times do
  done.receive
end

D[edit]

import std.stdio, std.random, std.parallelism, core.thread, core.time;

void main() {
    foreach (s; ["Enjoy", "Rosetta", "Code"].parallel(1)) {
        Thread.sleep(uniform(0, 1000).dur!"msecs");
        s.writeln;
    }
}

Alternative version[edit]

Library: Tango
import tango.core.Thread;
import tango.io.Console;
import tango.math.Random;

void main() {
    (new Thread( { Thread.sleep(Random.shared.next(1000) / 1000.0); Cout("Enjoy").newline; } )).start;
    (new Thread( { Thread.sleep(Random.shared.next(1000) / 1000.0); Cout("Rosetta").newline; } )).start;
    (new Thread( { Thread.sleep(Random.shared.next(1000) / 1000.0); Cout("Code").newline; } )).start;
}

Dart[edit]

Future[edit]

Using Futures, called Promises in Javascript

import 'dart:math' show Random;

main(){
	enjoy()   .then( (e) => print(e) );
	rosetta() .then( (r) => print(r) );
	code()    .then( (c) => print(c) );
}

// Create random number generator
var rng = Random();

// Each function returns a future that starts after a delay
// Like using setTimeout with a Promise in Javascript
enjoy()   => Future.delayed( Duration( milliseconds: rng.nextInt( 10 ) ), () => "Enjoy");
rosetta() => Future.delayed( Duration( milliseconds: rng.nextInt( 10 ) ), () => "Rosetta");
code()    => Future.delayed( Duration( milliseconds: rng.nextInt( 10 ) ), () => "Code");

Isolate[edit]

Using Isolates, similar to threads but each has its own memory, so they are more like Rust threads than C++

import 'dart:isolate' show Isolate, ReceivePort;
import 'dart:io'      show exit, sleep;
import 'dart:math'    show Random;

main() {
	// Create ReceivePort to receive done messages
	// Called a channel in other languages
	var receiver = ReceivePort();

	// Create job counter
	var job_count = 3;
	
	// Create job pool
	var jobs = [ enjoy, rosetta, code ];

	// Create random number generator
	var rng = Random();

	for ( var job in jobs ) {
		// Sleep for random duration up to half a second
		var sleep_time = Duration( milliseconds: rng.nextInt( 500 ) );	

		// Spawn  Isolate to do work
		// When finished the second argument will be sent to the receiver via the SendPort specified in onExit
		Isolate.spawn( job, sleep_time, onExit: receiver.sendPort );

	}
	
	// Do something in main isolate
	print("from main isolate\n");
	
	// Register a listener on the ReceivePort, it gets called whenver something is sent on its SendPort
	// We'll ignore the message with _ because we don't care about the data, just the event
	receiver.listen( (_) {
		// Decrement job counter
		job_count -= 1; 	
		// If jobs are all finished
		if ( job_count == 0 ) {
			print("\nall jobs finished!");
			exit(0);
		}
	});

}

enjoy ( duration ) { 
	sleep( duration ) ; 
	print("Enjoy"); 
}

rosetta ( duration ) {
	sleep( duration );
	print("Rosetta");
 }

code ( duration ) { 
	sleep( duration );
	print("Code");
}

Delphi[edit]

program ConcurrentComputing;

{$APPTYPE CONSOLE}

uses SysUtils, Classes, Windows;

type
  TRandomThread = class(TThread)
  private
    FString: string;
  protected
    procedure Execute; override;
  public
    constructor Create(const aString: string); overload;
  end;

constructor TRandomThread.Create(const aString: string);
begin
  inherited Create(False);
  FreeOnTerminate := True;
  FString := aString;
end;

procedure TRandomThread.Execute;
begin
  Sleep(Random(5) * 100);
  Writeln(FString);
end;

var
  lThreadArray: Array[0..2] of THandle;
begin
  Randomize;
  lThreadArray[0] := TRandomThread.Create('Enjoy').Handle;
  lThreadArray[1] := TRandomThread.Create('Rosetta').Handle;
  lThreadArray[2] := TRandomThread.Create('Stone').Handle;

  WaitForMultipleObjects(Length(lThreadArray), @lThreadArray, True, INFINITE);
end.

dodo0[edit]

fun parprint -> text, return
(
   fork() -> return, throw
      println(text, return)
   | x
   return()
)
| parprint

parprint("Enjoy") ->
parprint("Rosetta") ->
parprint("Code") ->

exit()

E[edit]

def base := timer.now()
for string in ["Enjoy", "Rosetta", "Code"] {
    timer <- whenPast(base + entropy.nextInt(1000), fn { println(string) })
}

Nondeterminism from preemptive concurrency rather than a random number generator:

def seedVat := <import:org.erights.e.elang.interp.seedVatAuthor>(<unsafe>)
for string in ["Enjoy", "Rosetta", "Code"] {
   seedVat <- (`
       fn string {
           println(string)
           currentVat <- orderlyShutdown("done")
       }
   `) <- get(0) <- (string)
}

EchoLisp[edit]

(lib 'tasks) ;; use the tasks library

(define (tprint line ) ;; task definition
		(writeln _TASK  line) 
		#f )
		
(for-each  task-run ;; run three // tasks
      (map (curry make-task tprint) '(Enjoy Rosetta code )))

   
   #task:id:66:running     Rosetta    
   #task:id:67:running     code    
   #task:id:65:running     Enjoy

Egel[edit]

import "prelude.eg"
import "io.ego"

using System
using IO

def main = 
    let _ = par (par [_ -> print "enjoy\n"] 
                    [_ -> print "rosetta\n"]) 
                [_ -> print "code\n"] in nop

Elixir[edit]

defmodule Concurrent do
  def computing(xs) do
    Enum.each(xs, fn x ->
      spawn(fn ->
        Process.sleep(:rand.uniform(1000))
        IO.puts x
      end)
    end)
    Process.sleep(1000)
  end
end
 
Concurrent.computing ["Enjoy", "Rosetta", "Code"]
Output:
Rosetta
Code
Enjoy

Erlang[edit]

hw.erl

-module(hw).
-export([start/0]).

start() ->
   [ spawn(fun() ->  say(self(), X) end) || X <- ['Enjoy', 'Rosetta', 'Code'] ],
   wait(2),
   ok.

say(Pid,Str) ->
   io:fwrite("~s~n",[Str]),
   Pid ! done.

wait(N) ->
   receive
       done -> case N of
           0 -> 0;
           _N -> wait(N-1)
       end
   end.

running it

|erlc hw.erl
|erl -run hw start -run init stop -noshell

Euphoria[edit]

procedure echo(sequence s)
    puts(1,s)
    puts(1,'\n')
end procedure

atom task1,task2,task3

task1 = task_create(routine_id("echo"),{"Enjoy"})
task_schedule(task1,1)

task2 = task_create(routine_id("echo"),{"Rosetta"})
task_schedule(task2,1)

task3 = task_create(routine_id("echo"),{"Code"})
task_schedule(task3,1)

task_yield()

Output:

Code
Rosetta
Enjoy

F#[edit]

We define a parallel version of Seq.iter by using asynchronous workflows:

module Seq =     
    let piter f xs =
        seq { for x in xs -> async { f x } }
        |> Async.Parallel
        |> Async.RunSynchronously
        |> ignore

let main() =  Seq.piter 
                (System.Console.WriteLine:string->unit)
                ["Enjoy"; "Rosetta"; "Code";]

main()

With version 4 of the .NET framework and F# PowerPack 2.0 installed, it is possible to use the predefined PSeq.iter instead.

Factor[edit]

USE: concurrency.combinators

{ "Enjoy" "Rosetta" "Code" } [ print ] parallel-each

Forth[edit]

Works with: gforth version 0.6.2

Many Forth implementations come with a simple cooperative task scheduler. Typically each task blocks on I/O or explicit use of the pause word. There is also a class of variables called "user" variables which contain task-specific data, such as the current base and stack pointers.

require tasker.fs
require random.fs

: task ( str len -- )
  64 NewTask 2 swap pass
  ( str len -- )
  10 0 do
    100 random ms
    pause 2dup cr type
  loop 2drop ;

: main
  s" Enjoy"   task
  s" Rosetta" task
  s" Code"    task
  begin pause single-tasking? until ;
main

Fortran[edit]

Fortran doesn't have threads but there are several compilers that support OpenMP, e.g. gfortran and Intel. The following code has been tested with thw Intel 11.1 compiler on WinXP.

program concurrency
  implicit none
  character(len=*), parameter :: str1 = 'Enjoy'
  character(len=*), parameter :: str2 = 'Rosetta'
  character(len=*), parameter :: str3 = 'Code'
  integer                     :: i
  real                        :: h
  real, parameter             :: one_third = 1.0e0/3
  real, parameter             :: two_thirds = 2.0e0/3

  interface
     integer function omp_get_thread_num
     end function omp_get_thread_num
  end interface
  interface
     integer function omp_get_num_threads
     end function omp_get_num_threads
  end interface

  ! Use OpenMP to create a team of threads
  !$omp parallel do private(i,h)
  do i=1,20
     ! First time through the master thread output the number of threads
     ! in the team
     if (omp_get_thread_num() == 0 .and. i == 1) then
        write(*,'(a,i0,a)') 'Using ',omp_get_num_threads(),' threads'
     end if

     ! Randomize the order
     call random_number(h)

     !$omp critical
     if (h < one_third) then
        write(*,'(a)') str1
     else if (h < two_thirds) then
        write(*,'(a)') str2
     else
        write(*,'(a)') str3
     end if
     !$omp end critical
  end do
  !$omp end parallel do

end program concurrency

FreeBASIC[edit]

' FB 1.05.0 Win64
' Compiled with -mt switch (to use threadsafe runtiume)
' The 'ThreadCall' functionality in FB is based internally on LibFFi (see [https://github.com/libffi/libffi/blob/master/LICENSE] for license)

Sub thread1()
  Print "Enjoy"
End Sub

Sub thread2()
  Print "Rosetta"
End Sub

Sub thread3()
  Print "Code"
End Sub

Print "Press any key to print next batch of 3 strings or ESC to quit"
Print

Do
  Dim t1 As Any Ptr = ThreadCall thread1
  Dim t2 As Any Ptr = ThreadCall thread2
  Dim t3 As Any Ptr = ThreadCall thread3
  ThreadWait t1
  ThreadWait t2
  ThreadWait t3
  Print
  Sleep
Loop While Inkey <> Chr(27)

Sample output

Output:
Press any key to print next batch of 3 strings or ESC to quit

Enjoy
Code
Rosetta

Enjoy
Rosetta
Code

FutureBasic[edit]

include "NSLog.incl"

long priority(2)
priority(0) = _dispatchPriorityDefault
priority(1) = _dispatchPriorityHigh
priority(2) = _dispatchPriorityLow

dispatchglobal , priority(rnd(3)-1)
  NSLog(@"Enjoy")
dispatchend

dispatchglobal , priority(rnd(3)-1)
  NSLog(@"Rosetta")
dispatchend

dispatchglobal , priority(rnd(3)-1)
  NSLog(@"Code")
dispatchend

HandleEvents

Go[edit]

Channel[edit]

Simple and direct solution: Start three goroutines, give each one a word. Each sleeps, then returns the word on a channel. The main goroutine prints words as they return. The print loop represents a checkpoint -- main doesn't exit until all words have been returned and printed.

This solution also shows a good practice for generating random numbers in concurrent goroutines. While certainly not needed for this RC task, in the more general case where you have a number of goroutines concurrently needing random numbers, the goroutines can suffer congestion if they compete heavily for the sole default library source. This can be relieved by having each goroutine create its own non-sharable source. Also particularly in cases where there might be a large number of concurrent goroutines, the source provided in subrepository rand package (exp/rand) can be a better choice than the standard library generator. The subrepo generator requires much less memory for "state" and is much faster to seed.

package main
  
import (
    "fmt"
    "golang.org/x/exp/rand"
    "time"
)

func main() {
    words := []string{"Enjoy", "Rosetta", "Code"}
    seed := uint64(time.Now().UnixNano())
    q := make(chan string)
    for i, w := range words {
        go func(w string, seed uint64) {
            r := rand.New(rand.NewSource(seed))
            time.Sleep(time.Duration(r.Int63n(1e9)))
            q <- w
        }(w, seed+uint64(i))
    }
    for i := 0; i < len(words); i++ {
        fmt.Println(<-q)
    }
}

Afterfunc[edit]

time.Afterfunc combines the sleep and the goroutine start. log.Println serializes output in the case goroutines attempt to print concurrently. sync.WaitGroup is used directly as a checkpoint.

package main

import (
    "log"
    "math/rand"
    "os"
    "sync"
    "time"
)

func main() {
    words := []string{"Enjoy", "Rosetta", "Code"}
    rand.Seed(time.Now().UnixNano())
    l := log.New(os.Stdout, "", 0)
    var q sync.WaitGroup
    q.Add(len(words))
    for _, w := range words {
        w := w
        time.AfterFunc(time.Duration(rand.Int63n(1e9)), func() {
            l.Println(w)
            q.Done()
        })
    }
    q.Wait()
}

Select[edit]

This solution might stretch the intent of the task a bit. It is concurrent but not parallel. Also it doesn't sleep and doesn't call the random number generator explicity. It works because the select statement is specified to make a "pseudo-random fair choice" among multiple channel operations.

package main

import "fmt"

func main() {
    w1 := make(chan bool, 1)
    w2 := make(chan bool, 1)
    w3 := make(chan bool, 1)
    for i := 0; i < 3; i++ {
        w1 <- true
        w2 <- true
        w3 <- true
        fmt.Println()
        for i := 0; i < 3; i++ {
            select {
            case <-w1:
                fmt.Println("Enjoy")
            case <-w2:
                fmt.Println("Rosetta")
            case <-w3:
                fmt.Println("Code")
            }
        }
    }
}

Output:

Code
Rosetta
Enjoy

Enjoy
Rosetta
Code

Rosetta
Enjoy
Code

Groovy[edit]

'Enjoy Rosetta Code'.tokenize().collect { w ->
    Thread.start {
        Thread.sleep(1000 * Math.random() as int)
        println w
    }
}.each { it.join() }

Haskell[edit]

Note how the map treats the list of processes just like any other data.

import Control.Concurrent

main = mapM_ forkIO [process1, process2, process3] where
  process1 = putStrLn "Enjoy" 
  process2 = putStrLn "Rosetta"
  process3 = putStrLn "Code"

A more elaborated example using MVars and a random running time per thread.

import Control.Concurrent
import System.Random

concurrent :: IO ()
concurrent = do
    var <- newMVar [] -- use an MVar to collect the results of each thread
    mapM_ (forkIO . task var) ["Enjoy", "Rosetta", "Code"] -- run 3 threads
    putStrLn "Press Return to show the results." -- while we wait for the user,
    -- the threads run
    _ <- getLine
    takeMVar var >>= mapM_ putStrLn -- read the results and show them on screen
    where
        -- "task" is a thread
        task v s = do
            randomRIO (1,10) >>= \r -> threadDelay (r * 100000) -- wait a while
            val <- takeMVar v -- read the MVar and block other threads from reading it
            -- until we write another value to it
            putMVar v (s : val) -- append a text string to the MVar and block other
            -- threads from writing to it unless it is read first

Icon and Unicon[edit]

The following code uses features exclusive to Unicon

procedure main()
   L:=[ thread write("Enjoy"), thread write("Rosetta"), thread write("Code") ]
   every wait(!L)
end

J[edit]

Example:

   smoutput&>({~?~@#);:'Enjoy Rosetta Code'
Rosetta
Code   
Enjoy

NOTES AND CAUTIONS:

1) While J's syntax and semantics is highly parallel, it is a deterministic sort of parallelism (analogous to the design of modern GPUs) and not the stochastic parallelism which is implied in this task specification (and which is usually obtained by timeslicing threads of control). The randomness implemented here is orthogonal to the parallelism in the display (and you could remove smoutput& without altering the appearence, in this trivial example).

2) The current release of J (and the past implementations) do not implement hardware based concurrency. This is partially an economic issue (since all of the current and past language implementations have been distributed for free, with terms which allow free distribution), and partially a hardware maturity issue (historically, most CPU multi-core development has been optimized for stochastic parallelism with minimal cheap support for large scale deterministic parallelism and GPUs have not been capable of supporting the kind of generality needed by J).

This state of affairs is likely to change, eventually (most likely this will be after greater than factor of 2 speedups from hardware parallelism are available for the J users in cases which are common and important enough to support the implementation). But, for now, J's parallelism is entirely conceptual.

Java[edit]

Works with: Java version 1.5+

Uses CyclicBarrier to force all threads to wait until they're at the same point before executing the println, increasing the odds they'll print in a different order (otherwise, while the they may be executing in parallel, the threads are started sequentially and with such a short run-time, will usually output sequentially as well).

import java.util.concurrent.CyclicBarrier;

public class Threads
{
  public static class DelayedMessagePrinter implements Runnable
  {
    private CyclicBarrier barrier;
    private String msg;
    
    public DelayedMessagePrinter(CyclicBarrier barrier, String msg)
    {
      this.barrier = barrier;
      this.msg = msg;
    }
    
    public void run()
    {
      try
      {  barrier.await();  }
      catch (Exception e)
      {  }
      System.out.println(msg);
    }
  }
  
  public static void main(String[] args)
  {
    CyclicBarrier barrier = new CyclicBarrier(3);
    new Thread(new DelayedMessagePrinter(barrier, "Enjoy")).start();
    new Thread(new DelayedMessagePrinter(barrier, "Rosetta")).start();
    new Thread(new DelayedMessagePrinter(barrier, "Code")).start();
  }
}

JavaScript[edit]

JavaScript now enjoys access to a concurrency library thanks to Web Workers. The Web Workers specification defines an API for spawning background scripts. This first code is the background script and should be in the concurrent_worker.js file.

self.addEventListener('message', function (event) {
  self.postMessage(event.data);
  self.close();
}, false);

This second block creates the workers, sends them a message and creates an event listener to handle the response.

var words = ["Enjoy", "Rosetta", "Code"];
var workers = [];

for (var i = 0; i < words.length; i++) {
  workers[i] = new Worker("concurrent_worker.js");
  workers[i].addEventListener('message', function (event) {
    console.log(event.data);
  }, false);
  workers[i].postMessage(words[i]);
}

Julia[edit]

Works with: Julia version 0.6
words = ["Enjoy", "Rosetta", "Code"]

function sleepprint(s)
    sleep(rand())
    println(s)
end

@sync for word in words
    @async sleepprint(word)
end

Kotlin[edit]

Translation of: Java
// version 1.1.2

import java.util.concurrent.CyclicBarrier

class DelayedMessagePrinter(val barrier: CyclicBarrier, val msg: String) : Runnable {
    override fun run() {
        barrier.await()
        println(msg)
    }
}

fun main(args: Array<String>) {
    val msgs = listOf("Enjoy", "Rosetta", "Code")
    val barrier = CyclicBarrier(msgs.size)
    for (msg in msgs) Thread(DelayedMessagePrinter(barrier, msg)).start()
}
Output:

Sample output:

Code
Rosetta
Enjoy

LFE[edit]

;;;
;;;   This is a straight port of the Erlang version.
;;;
;;;   You can run this under the LFE REPL as follows:
;;;
;;;   (slurp "concurrent-computing.lfe")
;;;   (start)
;;;
(defmodule concurrent-computing
  (export (start 0)))

(defun start ()
  (lc ((<- word '("Enjoy" "Rosetta" "Code")))
    (spawn (lambda () (say (self) word))))
  (wait 2)
  'ok)

(defun say (pid word)
  (lfe_io:format "~p~n" (list word))
  (! pid 'done))

(defun wait (n)
  (receive
    ('done (case n
             (0 0)
             (_n (wait (- n 1)))))))

Logtalk[edit]

Works when using SWI-Prolog, XSB, or YAP as the backend compiler.

:- object(concurrency).

    :- initialization(output).

    output :-
        threaded((
            write('Enjoy'),
            write('Rosetta'),
            write('Code')
        )).

:- end_object.

Lua[edit]

co = {}
co[1] = coroutine.create( function() print "Enjoy" end )
co[2] = coroutine.create( function() print "Rosetta" end )
co[3] = coroutine.create( function() print "Code" end )

math.randomseed( os.time() )
h = {}
i = 0
repeat
    j = math.random(3)
    if h[j] == nil then
       coroutine.resume( co[j] )
       h[j] = true
       i = i + 1
    end
until i == 3

M2000 Interpreter[edit]

Each thread executed in same scope where created. We can use static variables, which are at thread level, so in this example we have three A$,one for each thread. Each thread can use Thread This to send command, or using a known handler (number which return to k) to execute commands to other threads. Commands are HOLD,RESTART, ERASE, INTERVAL, EXECUTE.

Each thread has own stack of values, which deleted when erased. We can Push values to top of stack, or use Data to push to end of stack. A Read statement read from top of stack. In the example we Flush module's stack (modules use parent stack, functions get own stack), we place with Data strings and we read it using Read M$. We place the M$ to Static A$ (this can be done one time, because if A$ as static exist then interpreter skip expression without execute it).

All threads of a module erased when a module exit. Any block of code inside { } in Thread run without concurrency, when we use Thread.Plan Concurrent (when a thread runs we can't change Plan). Other plan is the sequential. Interval can be set to milliseconds.

Threads actually runs in Wait loop. We can use Main.Task as a loop which is thread also. Threads can be run when we wait for input in m2000 console, or for events from M2000 GUI forms, also. Events always run in sequential form.

Thread.Plan Concurrent
Module CheckIt {
      Flush  \\ empty stack of values
      Data "Enjoy", "Rosetta", "Code"
      For i=1 to 3 {
            Thread {
                  Print A$
                  Thread This Erase
            } As K
            Read M$
            Thread K Execute Static A$=M$
            Thread K Interval Random(500,1000)
            Threads
      }
      Rem : Wait 3000   ' we can use just a wait loop, or the main.task loop
      \\ main.task exit if all threads erased
      Main.Task 30 {
      }
\\ when module exit all threads from this module get a signal to stop.
\\ we can use Threads Erase to erase all threads.
\\ Also if we press Esc we do the same
}
CheckIt

\\ we can define again the module, and now we get three time each name, but not every time three same names.
\\ if we change to Threads.Plan Sequential we get always the three same names
\\ Also in concurrent plan we can use a block to ensure that statements run without other thread executed in parallel.

Module CheckIt {
      Flush  \\ empty stack of values
      Data "Enjoy", "Rosetta", "Code"
      For i=1 to 3 {
            Thread {
                  Print A$
                  Print A$
                  Print A$
                  Thread This Erase
            } As K
            Read M$
            Thread K Execute Static A$=M$
            Thread K Interval Random(500,530)
            Threads
      }
      Rem : Wait 3000   ' we can use just a wait loop, or the main.task loop
      \\ main.task exit if all threads erased
      Main.Task 30 {
      }
\\ when module exit all threads from this module get a signal to stop.
\\ we can use Threads Erase to erase all threads.
\\ Also if we press Esc we do the same
}
CheckIt

Mathematica / Wolfram Language[edit]

Parallelization requires Mathematica 7 or later

ParallelDo[
    Pause[RandomReal[]];
    Print[s],
    {s, {"Enjoy", "Rosetta", "Code"}}
]

Mercury[edit]

:- module concurrent_computing.
:- interface.

:- import_module io.
:- pred main(io::di, io::uo) is cc_multi.

:- implementation.
:- import_module thread.

main(!IO) :-
   spawn(io.print_cc("Enjoy\n"), !IO),
   spawn(io.print_cc("Rosetta\n"), !IO),
   spawn(io.print_cc("Code\n"), !IO).

Neko[edit]

/**
 Concurrent computing, in Neko
*/

var thread_create = $loader.loadprim("std@thread_create", 2);

var subtask = function(message) {
  $print(message, "\n");
}

/* The thread functions happen so fast as to look sequential */
thread_create(subtask, "Enjoy");
thread_create(subtask, "Rosetta");
thread_create(subtask, "Code");

/* slow things down */
var sys_sleep = $loader.loadprim("std@sys_sleep", 1);
var random_new = $loader.loadprim("std@random_new", 0);
var random_int = $loader.loadprim("std@random_int", 2);

var randomsleep = function(message) {
  var r = random_new();
  var sleep = random_int(r, 3);
  sys_sleep(sleep);
  $print(message, "\n");
}

$print("\nWith random delays\n");
thread_create(randomsleep, "Enjoy");
thread_create(randomsleep, "Rosetta");
thread_create(randomsleep, "Code");

/* Let the threads complete */
sys_sleep(4);
Output:
prompt$ nekoc threading.neko
prompt$ neko threading      
Enjoy
Rosetta
Code

With random delays
Rosetta
Enjoy
Code

Nim[edit]

Compile with nim --threads:on c concurrent:

const str = ["Enjoy", "Rosetta", "Code"]

var thr: array[3, Thread[int32]]

proc f(i:int32) {.thread.} =
  echo str[i]

for i in 0..thr.high:
  createThread(thr[i], f, int32(i))
joinThreads(thr)

OpenMP[edit]

Compile with nim --passC:"-fopenmp" --passL:"-fopenmp" c concurrent:

const str = ["Enjoy", "Rosetta", "Code"]

for i in 0||2:
  echo str[i]

Thread Pools[edit]

Compile with nim --threads:on c concurrent:

import threadpool
const str = ["Enjoy", "Rosetta", "Code"]

proc f(i: int) {.thread.} =
  echo str[i]

for i in 0..str.high:
  spawn f(i)
sync()

Objeck[edit]

bundle Default {
  class MyThread from Thread {
    New(name : String) {
      Parent(name);
    }

    method : public : Run(param : Base) ~ Nil {
      string := param->As(String);
      string->PrintLine();
    }
  }

  class Concurrent {
    New() {
    }

    function : Main(args : System.String[]) ~ Nil {
      t0 := MyThread->New("t0");
      t1 := MyThread->New("t1");
      t2 := MyThread->New("t2");

      t0->Execute("Enjoy"->As(Base));
      t1->Execute("Rosetta"->As(Base));
      t2->Execute("Code"->As(Base));
    }
  }
}

OCaml[edit]

#directory "+threads"
#load "unix.cma"
#load "threads.cma"

let sleepy_print msg =
  Unix.sleep (Random.int 4);
  print_endline msg

let threads =
  List.map (Thread.create sleepy_print) ["Enjoy"; "Rosetta"; "Code"]

let () =
  Random.self_init ();
  List.iter (Thread.join) threads

Oforth[edit]

Oforth uses tasks to implement concurrent computing. A task is scheduled using #& on a function, method, block, ...

#[ "Enjoy" println ] & 
#[ "Rosetta" println ] & 
#[ "Code" println ] &

mapParallel method can be used to map a runnable on each element of a collection and returns a collection of results. Here, we println the string and return string size.

[ "Enjoy", "Rosetta", "Code" ] mapParallel(#[ dup . size ])

Ol[edit]

(import (otus random!))

(for-each (lambda (str)
      (define timeout (rand! 999))
      (async (lambda ()
         (sleep timeout)
         (print str))))
   '("Enjoy" "Rosetta" "Code"))
Output:
Code
Enjoy
Rosetta

ooRexx[edit]

-- this will launch 3 threads, with each thread given a message to print out.
-- I've added a stoplight to make each thread wait until given a go signal,
-- plus some sleeps to give the threads a chance to randomize the execution
-- order a little.
launcher = .launcher~new
launcher~launch

::class launcher
-- the launcher method.  Guarded is the default, but let's make this
-- explicit here
::method launch guarded

  runner1 = .runner~new(self, "Enjoy")
  runner2 = .runner~new(self, "Rosetta")
  runner3 = .runner~new(self, "Code")

  -- let's give the threads a chance to settle in to the
  -- starting line
  call syssleep 1

  guard off   -- release the launcher lock.  This is the starter's gun

-- this is a guarded method that the runners will call.  They
-- will block until the launch method releases the object guard
::method block guarded

::class runner
::method init
  use arg launcher, text
  reply  -- this creates the new thread

  call syssleep .5  -- try to mix things up by sleeping
  launcher~block    -- wait for the go signal
  call syssleep .5  -- add another sleep here
  say text

Oz[edit]

The randomness comes from the unpredictability of thread scheduling (this is how I understand this exercise).

for Msg in ["Enjoy" "Rosetta" "Code"] do
   thread
      {System.showInfo Msg}
   end
end

PARI/GP[edit]

Here is a GP implementation using the bill-mt branch:

inline(func);
func(n)=print(["Enjoy","Rosetta","Code"][n]);
parapply(func,[1..3]);

This is a PARI implementation which uses fork() internally. Note that the C solutions can be used instead if desired; this program demonstrates the native PARI capabilities instead.

For serious concurrency, see Appendix B of the User's Guide to the PARI Library which discusses a solution using tls on pthreads. (There are nontrivial issues with using PARI in this environment, do not attempt to blindly implement a C solution.)

void
foo()
{
  if (pari_daemon()) {
    // Original
    if (pari_daemon()) {
      // Original
      pari_printf("Enjoy\n");
    } else {
      // Daemon #2
      pari_printf("Code\n");
    }
  } else {
    // Daemon #1
    pari_printf("Rosetta\n");
  }
}

See also Bill Allombert's slides on parallel programming in GP.

Pascal[edit]

Translation of: Delphi
modified for linux. Using simple running thread-counter to circumvent WaitForMultipleObjects.

Output of difference of sleep time and true sleep time ( running with 0..1999 threads you see once a while 1)

program ConcurrentComputing;
{$IFdef FPC}
  {$MODE DELPHI}
{$ELSE}
  {$APPTYPE CONSOLE}
{$ENDIF}
uses
  {$IFDEF UNIX}
    cthreads,
  {$ENDIF}
  SysUtils, Classes;

type
  TRandomThread = class(TThread)
  private
    FString: string;
    T0 : Uint64;
  protected
    procedure Execute; override;
  public
    constructor Create(const aString: string); overload;
  end;
const
  MyStrings: array[0..2] of String = ('Enjoy ','Rosetta ','Code ');
var
  gblRunThdCnt : LongWord = 0;

constructor TRandomThread.Create(const aString: string);
begin
  inherited Create(False);
  FreeOnTerminate := True;
  FString := aString;
  interlockedincrement(gblRunThdCnt);
end;

procedure TRandomThread.Execute;
var
  i : NativeInt;
begin
  i := Random(300);
  T0 := GettickCount64;
  Sleep(i);
  //output of difference in time
  Writeln(FString,i:4,GettickCount64-T0 -i:2);
  interlockeddecrement(gblRunThdCnt);
end;

var
  lThreadArray: Array[0..9] of THandle;
  i : NativeInt;
begin
  Randomize;

  gblRunThdCnt := 0;
  For i := low(lThreadArray) to High(lThreadArray) do
    lThreadArray[i] := TRandomThread.Create(Format('%9s %4d',[myStrings[Random(3)],i])).Handle;

  while gblRunThdCnt > 0 do
    sleep(125);
end.
Output:
   Enjoy    4  16 0
    Code    0  22 0
    Code    1  32 0
 Rosetta    7 117 0
   Enjoy    2 137 0
    Code    6 214 0
    Code    5 252 0
   Enjoy    3 299 0

Perl[edit]

use threads;
use Time::HiRes qw(sleep);

$_->join for map {
    threads->create(sub {
        sleep rand;
        print shift, "\n";
    }, $_)
} qw(Enjoy Rosetta Code);
Or using coroutines provided by
Library: Coro
use feature qw( say );
use Coro;
use Coro::Timer qw( sleep );

$_->join for map {
    async {
        sleep rand; 
        say @_;
    } $_
} qw( Enjoy Rosetta Code );

Phix[edit]

Without the sleep it is almost always Enjoy Rosetta Code, because create_thread() is more costly than echo(), as the former has to create a new call stack etc.
The lock prevents the displays from mangling each other.

without js -- (threads)
procedure echo(string s)
    sleep(rand(100)/100)
    enter_cs()
    puts(1,s)
    puts(1,'\n')
    leave_cs()
end procedure
 
constant threads = {create_thread(routine_id("echo"),{"Enjoy"}),
                    create_thread(routine_id("echo"),{"Rosetta"}),
                    create_thread(routine_id("echo"),{"Code"})}
 
wait_thread(threads)
puts(1,"done")
{} = wait_key()

PicoLisp[edit]

Using background tasks[edit]

(for (N . Str) '("Enjoy" "Rosetta" "Code")
   (task (- N) (rand 1000 4000)              # Random start time 1 .. 4 sec
      Str Str                                # Closure with string value
      (println Str)                          # Task body: Print the string
      (task @) ) )                           # and stop the task

Using child processes[edit]

(for Str '("Enjoy" "Rosetta" "Code")
   (let N (rand 1000 4000)                   # Randomize
      (unless (fork)                         # Create child process
         (wait N)                            # Wait 1 .. 4 sec
         (println Str)                       # Print string
         (bye) ) ) )                         # Terminate child process

Pike[edit]

Using POSIX threads:

int main() {
	// Start threads and wait for them to finish
	({
		Thread.Thread(write, "Enjoy\n"),
		Thread.Thread(write, "Rosetta\n"),
		Thread.Thread(write, "Code\n")
	})->wait();
	
	// Exit program
	exit(0);
}

Output:

Enjoy
Rosetta
Code

Using Pike's backend:

int main(int argc, array argv)
{
    call_out(write, random(1.0), "Enjoy\n");
    call_out(write, random(1.0), "Rosetta\n");
    call_out(write, random(1.0), "Code\n");
    call_out(exit, 1, 0);
    return -1; // return -1 starts the backend which makes Pike run until exit() is called.
}

Output:

Rosetta
Code
Enjoy

PowerShell[edit]

Using Background Jobs:

$Strings = "Enjoy","Rosetta","Code"

$SB = {param($String)Write-Output $String}

foreach($String in $Strings) {
    Start-Job -ScriptBlock $SB -ArgumentList $String | Out-Null    
    }

Get-Job | Wait-Job | Receive-Job
Get-Job | Remove-Job

Using .NET Runspaces:

$Strings = "Enjoy","Rosetta","Code"

$SB = {param($String)Write-Output $String}

$Pool = [RunspaceFactory]::CreateRunspacePool(1, 3)
$Pool.ApartmentState = "STA"
$Pool.Open()
foreach ($String in $Strings) {
    $Pipeline  = [System.Management.Automation.PowerShell]::create()
    $Pipeline.RunspacePool = $Pool
    [void]$Pipeline.AddScript($SB).AddArgument($String)
    $AsyncHandle = $Pipeline.BeginInvoke()
    $Pipeline.EndInvoke($AsyncHandle)
    $Pipeline.Dispose()
    }
$Pool.Close()

Prolog[edit]

This example works in SWI-Prolog. It may work in other Prolog implementations too.

Create a separate thread for each word. Join the threads to make sure they complete before the program exits.

main :-
    thread_create(say("Enjoy"),A,[]),
    thread_create(say("Rosetta"),B,[]),
    thread_create(say("Code"),C,[]),
    thread_join(A,_),
    thread_join(B,_),
    thread_join(C,_).

say(Message) :-
    Delay is random_float,
    sleep(Delay),
    writeln(Message).

PureBasic[edit]

Global mutex = CreateMutex()

Procedure Printer(*str)
	LockMutex(mutex)
	PrintN( PeekS(*str) )
	UnlockMutex(mutex)
EndProcedure

If OpenConsole()
	LockMutex(mutex)
	thread1 = CreateThread(@Printer(), @"Enjoy")
	thread2 = CreateThread(@Printer(), @"Rosetta")
	thread3 = CreateThread(@Printer(), @"Code")
	UnlockMutex(mutex)
	
	WaitThread(thread1)
	WaitThread(thread2)
	WaitThread(thread3)
	
	Print(#CRLF$ + #CRLF$ + "Press ENTER to exit")
	Input()
	
	CloseConsole()
EndIf

FreeMutex(mutex)

Python[edit]

Works with: Python version 3.7

Using asyncio module (I know almost nothing about it, so feel free to improve it :-)):

import asyncio


async def print_(string: str) -> None:
    print(string)


async def main():
    strings = ['Enjoy', 'Rosetta', 'Code']
    coroutines = map(print_, strings)
    await asyncio.gather(*coroutines)


if __name__ == '__main__':
    asyncio.run(main())
Works with: Python version 3.2

Using the new to Python 3.2 concurrent.futures library and choosing to use processes over threads; the example will use up to as many processes as your machine has cores. This doesn't however guarantee an order of sub-process results.

Python 3.2 (r32:88445, Feb 20 2011, 21:30:00) [MSC v.1500 64 bit (AMD64)] on win 32
Type "help", "copyright", "credits" or "license" for more information.
>>> from concurrent import futures
>>> with futures.ProcessPoolExecutor() as executor:
...   _ = list(executor.map(print, 'Enjoy Rosetta Code'.split()))
...
Enjoy
Rosetta
Code
>>>
Works with: Python version 2.5
import threading
import random
 
def echo(text):
    print(text)
 
threading.Timer(random.random(), echo, ("Enjoy",)).start()
threading.Timer(random.random(), echo, ("Rosetta",)).start()
threading.Timer(random.random(), echo, ("Code",)).start()

Or, by using a for loop to start one thread per list entry, where our list is our set of source strings:

import threading
import random

def echo(text):
    print(text)

for text in ["Enjoy", "Rosetta", "Code"]:
    threading.Timer(random.random(), echo, (text,)).start()

threading.Thread[edit]

import random, sys, time
import threading

lock = threading.Lock()

def echo(s):
    time.sleep(1e-2*random.random())
    # use `.write()` with lock due to `print` prints empty lines occasionally
    with lock:
        sys.stdout.write(s)
        sys.stdout.write('\n')

for line in 'Enjoy Rosetta Code'.split():
    threading.Thread(target=echo, args=(line,)).start()

multiprocessing[edit]

Works with: Python version 2.6
from __future__ import print_function
from multiprocessing import Pool

def main():
    p = Pool()
    p.map(print, 'Enjoy Rosetta Code'.split())

if __name__=="__main__":
    main()

twisted[edit]

import random
from twisted.internet    import reactor, task, defer
from twisted.python.util import println

delay = lambda: 1e-4*random.random()
d = defer.DeferredList([task.deferLater(reactor, delay(), println, line)
                        for line in 'Enjoy Rosetta Code'.split()])
d.addBoth(lambda _: reactor.stop())
reactor.run()

gevent[edit]

from __future__ import print_function
import random
import gevent

delay = lambda: 1e-4*random.random()
gevent.joinall([gevent.spawn_later(delay(), print, line)
               for line in 'Enjoy Rosetta Code'.split()])

Racket[edit]

Threads provide a simple API for concurrent programming.

#lang racket
(for ([str '("Enjoy" "Rosetta" "Code")])
  (thread (λ () (displayln str))))

In addition to "thread" which is implemented as green threads (useful for IO etc), Racket has "futures" and "places" which are similar tools for using multiple OS cores.

Raku[edit]

(formerly Perl 6)

Works with: Rakudo version 2018.9
my @words = <Enjoy Rosetta Code>;
@words.race(:batch(1)).map: { sleep rand; say $_ };
Output:
Code
Rosetta
Enjoy

Raven[edit]

[ 'Enjoy' 'Rosetta' 'Code' ] as $words

thread talker
    $words pop "%s\n"
    repeat dup print
        500 choose ms

talker as a
talker as b
talker as c

Rhope[edit]

Works with: Rhope version alpha 1
Main(0,0)
|:
    Print["Enjoy"]
    Print["Rosetta"]
    Print["Code"]
:|

In Rhope, expressions with no shared dependencies run in parallel by default.

Ruby[edit]

%w{Enjoy Rosetta Code}.map do |x|
    Thread.new do
        sleep rand
        puts x
    end
end.each do |t| 
  t.join
end

Rust[edit]

Library: rand
extern crate rand;
use std::thread;
use rand::thread_rng;
use rand::distributions::{Range, IndependentSample};

fn main() {
    let mut rng = thread_rng();
    let rng_range = Range::new(0u32, 100);
    for word in "Enjoy Rosetta Code".split_whitespace() {
        let snooze_time = rng_range.ind_sample(&mut rng);
        let local_word = word.to_owned();
        std::thread::spawn(move || {
            thread::sleep_ms(snooze_time);
            println!("{}", local_word);
        });
    }
    thread::sleep_ms(1000);
}

Scala[edit]

import scala.actors.Futures
List("Enjoy", "Rosetta", "Code").map { x =>
    Futures.future {                           
      Thread.sleep((Math.random * 1000).toInt)   
       println(x)                                 
    }         
}.foreach(_())

Scheme[edit]

(parallel-execute (lambda () (print "Enjoy"))
                  (lambda () (print "Rosetta"))
                  (lambda () (print "Code")))

If your implementation doesn't provide parallel-execute, it can be implemented with SRFI-18.

(import (srfi 18))
(define (parallel-execute . thunks)
 (let ((threads (map make-thread thunks)))
  (for-each thread-start! threads)
  (for-each thread-join! threads)))

Sidef[edit]

A very basic threading support is provided by the Block.fork() method:

var a = <Enjoy Rosetta Code>

a.map{|str|
    {   Sys.sleep(1.rand)
        say str
    }.fork
}.map{|thr| thr.wait }
Output:
Enjoy
Code
Rosetta

Slope[edit]

(coeval
  (display "Enjoy")
  (display "Rosetta")
  (display "Code"))

Swift[edit]

Using Grand Central Dispatch with concurrent queues.

import Foundation

let myList = ["Enjoy", "Rosetta", "Code"]

for word in myList {
    dispatch_async(dispatch_get_global_queue(0, 0)) {
        NSLog(word)
    }
}

dispatch_main()
Output:
2015-02-05 10:15:01.831 rosettaconcurrency[1917:37905] Code
2015-02-05 10:15:01.831 rosettaconcurrency[1917:37902] Enjoy
2015-02-05 10:15:01.831 rosettaconcurrency[1917:37904] Rosetta

Standard ML[edit]

Works with PolyML

structure TTd  =  Thread.Thread ;
structure TTm  =  Thread.Mutex  ;

val threadedStringList =  fn tasks:string list  =>
 let
  val mx        =  TTm.mutex () ;
  val taskstore =  ref tasks ;
  fun makeFastRand () =  Real.rem (Time.toReal (Time.now ()),1.0) 
  val doTask =  fn () =>
   let
    val mytask :  string  ref   = ref "" ;
   in
   (   TTm.lock mx ; mytask :=  hd ( !taskstore ) ;  taskstore:= tl (!taskstore) ; TTm.unlock mx ;
       Posix.Process.sleep (Time.fromReal (makeFastRand ())) ;
       TTm.lock mx ; print ( !mytask ^ "\n")  ;   TTm.unlock mx ;
       TTd.exit ()
   ) 
   end
in

 List.tabulate ( length tasks , fn i => TTd.fork (doTask , []) ) 
 
end ;

call

threadedStringList  [ "Enjoy","Rosetta","Code" ];
Rosetta
Code
Enjoy

Tcl[edit]

Assuming that "random" means that we really want the words to appear in random (rather then "undefined" or "arbitrary") order:

after [expr int(1000*rand())] {puts "Enjoy"}
after [expr int(1000*rand())] {puts "Rosetta"}
after [expr int(1000*rand())] {puts "Code"}

will execute each line after a randomly chosen number (0...1000) of milliseconds.

A step towards "undefined" would be to use after idle, which is Tcl for "do this whenever you get around to it". Thus:

after idle {puts "Enjoy"}
after idle {puts "Rosetta"}
after idle {puts "Code"}

(While no particular order is guaranteed by the Tcl spec, the current implementations will all execute these in the order in which they were added to the idle queue).

It's also possible to use threads for this. Here we do this with the built-in thread-pool support:

package require Thread
set pool [tpool::create -initcmd {
    proc delayPrint msg {
        after [expr int(1000*rand())]
        puts $msg
    }
}]
tpool::post -detached $pool [list delayPrint "Enjoy"]
tpool::post -detached $pool [list delayPrint "Rosetta"]
tpool::post -detached $pool [list delayPrint "Code"]
tpool::release $pool
after 1200 ;# Give threads time to do their work
exit

UnixPipes[edit]

(echo "Enjoy" & echo "Rosetta"& echo "Code"&)

VBA[edit]

Three tasks scheduled for the same time with OnTime. The last scheduled task gets executed first.

Private Sub Enjoy()
    Debug.Print "Enjoy"
End Sub
Private Sub Rosetta()
    Debug.Print "Rosetta"
End Sub
Private Sub Code()
    Debug.Print "Code"
End Sub
Public Sub concurrent()
    when = Now + TimeValue("00:00:01")
    Application.OnTime when, "Enjoy"
    Application.OnTime when, "Rosetta"
    Application.OnTime when, "Code"
End Sub

Visual Basic .NET[edit]

Imports System.Threading

Module Module1
   Public rnd As New Random

   Sub Main()
       Dim t1 As New Thread(AddressOf Foo)
       Dim t2 As New Thread(AddressOf Foo)
       Dim t3 As New Thread(AddressOf Foo)

       t1.Start("Enjoy")
       t2.Start("Rosetta")
       t3.Start("Code")

       t1.Join()
       t2.Join()
       t3.Join()

   End Sub

   Sub Foo(ByVal state As Object)
       Thread.Sleep(rnd.Next(1000))
       Console.WriteLine(state)
   End Sub

End Module

Alternative version[edit]

Try It Online!

Imports System.Threading
Module Module1
    Dim rnd As New Random()
    Sub Main()
        Parallel.ForEach("Enjoy Rosetta Code".Split(" "), Sub(s)
            Thread.Sleep(rnd.Next(25)) : Console.WriteLine(s)
        End Sub)
    End Sub
End Module
Output:
Rosetta
Enjoy
Code

Vlang[edit]

Porting of Go code[edit]

import time
import rand
import rand.pcg32
import rand.seed

fn main() {
    words := ['Enjoy', 'Rosetta', 'Code']
    seed_u64 := u64(time.now().unix_time_milli())
    q := chan string{}
    for i, w in words {
        go fn (q chan string, w string, seed_u64 u64) {
            mut rng := pcg32.PCG32RNG{}
            time_seed := seed.time_seed_array(2)
            seed_arr := [u32(seed_u64), u32(seed_u64 >> 32), time_seed[0], time_seed[1]]
            rng.seed(seed_arr)
            time.sleep(time.Duration(rng.i64n(1_000_000_000)))
            q <- w
        }(q, w, seed_u64 + u64(i))
    }
    for _ in 0 .. words.len {
        println(<-q)
    }
}

Vlang Idiomatic version[edit]

import time
import rand
import rand.pcg32
import rand.seed

fn main() {
    words := ['Enjoy', 'Rosetta', 'Code']
    mut threads := []thread{} // mutable array to hold the id of the thread
    for w in words {
        threads << go fn (w string) { // record the thread
            mut rng := pcg32.PCG32RNG{}
            time_seed := seed.time_seed_array(4) // the time derived array to seed the random generator
            rng.seed(time_seed)
            time.sleep(time.Duration(rng.i64n(1_000_000_000)))
            println(w)
        }(w)
    }
    threads.wait() // join the thread waiting. wait() is defined for threads and arrays of threads
}
Output:
Code

Rosetta Enjoy

Rosetta Enjoy

Code

Wren[edit]

import "random" for Random

var words = ["Enjoy", "Rosetta", "Code"]
var rand = Random.new()
for (h in 1..3) {
    var fibers = List.filled(3, null)
    for (i in 0..2) fibers[i] = Fiber.new { System.print(words[i]) }
    var called = List.filled(3, false)
    var j = 0
    while (j < 3) {
        var k = rand.int(3)
        if (!called[k]) {
            fibers[k].call()
            called[k] = true
            j = j + 1
        }
    }
    System.print()
}
Output:

Sample run:

Enjoy
Code
Rosetta

Code
Enjoy
Rosetta

Rosetta
Enjoy
Code

XPL0[edit]

Works on Raspberry Pi using XPL0 version 3.2. Processes actually execute simultaneously, one per CPU core (beyond single-core RPi-1). Lock is necessary to enable one line to finish printing before another line starts.

int Key, Process;
[Key:= SharedMem(4);    \allocate 4 bytes of memory common to all processes
Process:= Fork(2);      \start 2 child processes
case Process of
  0:  [Lock(Key);  Text(0, "Enjoy");    CrLf(0);  Unlock(Key)]; \parent process
  1:  [Lock(Key);  Text(0, "Rosetta");  CrLf(0);  Unlock(Key)]; \child process
  2:  [Lock(Key);  Text(0, "Code");     CrLf(0);  Unlock(Key)]  \child process
other [Lock(Key);  Text(0, "Error");    CrLf(0);  Unlock(Key)];
Join(Process);          \wait for all child processes to finish
]
Output:
Code
Enjoy
Rosetta

zkl[edit]

fcn{println("Enjoy")}.launch();  // thread
fcn{println("Rosetta")}.strand();  // co-op thread
fcn{println("Code")}.future();  // another thread type
Output:
Rosetta
Code
Enjoy