Process is the running instance of program, so to execute any program we need to create a process, there are various defined procedures depending on language for creation of process.

For example in C, we use fork and spawn in Erlang. If you are a computer science student, you might have come across the term fork in your operating systems course, as far as Erlang is concerned you might not have heard about it.

Before I go to the process creation in both the languages, I will encourage you to read something about Erlang on internet.

Process creation in C

  #include <stdio.h>
  #include <sys/types.h
  #include <unistd.h>
  #include <stdlib.h>
  #include <errno.h>
  int child = 0, parent = 0;
  int main(void){
  int numProcess = 10;
  for(int i=0; i<numProcess; i++){
    pid_t  pid;
    /* Output from both the child and the parent process
    * will be written to the standard output,
    * as they both run at the same time.
    */

    pid = fork();

    if (pid == -1){
      /* Error:
       * When fork() returns -1, an error happened
       * (for example, number of processes reached the limit).
       */
      fprintf(stderr, "can't fork, error %d\n", errno);
      exit(EXIT_FAILURE);
    }else if (pid == 0){
      /* Child process:
       */
       printf("\nchild process : %d\n",child);
       child+=1;
    }else{
      // parent process
      printf("\nparent process : %d\n",parent);
      parent+=1;
    }
  }
  return 0;
}

For executing this program save the code as process_c.c and then execute

1. gcc process_c.c
2. ./a.out

You can the value of number of processes, change the value of numProcess in program

Process creation in Erlang

-module(process_erlang).
-export([chain/1]).

chain(0) ->
	receive
		_ -> ok
	after 2000 ->
		process_flag(trap_exit, true)
	end;

chain(N) ->
	Pid = spawn(fun() -> chain(N-1) end),
	link(Pid),
	io:format("~nprocess ~p created, Pid :: ~p ~n",[N,Pid]),
	receive
		_ -> ok
	end.

For executing above Erlang code, save the file as process_erlang.erl then

1. Start erl monitor by typing erl on terminal
2. c(process_erlang).
3. link(spawn(process_erlang, chain, [100])).

At the place of 100 in step 3, you can set value of choice depending on number of processes.

Comparison of process creation time

Processes of Erlang are very light weight as compared to processes of C and thus time taken by Erlang processes is very less as compared to in C, see graph images for comparison of process creation time in Erlang, Java and C# here

Try out yourself in the C program set numProcess = 100, your system will stop responding and you need to restart the system, instead in case of Erlang set value to 200 instead of 100 and all the processes will be created within a second(didn’t calculated actual time).

The comparison of Erlang processes and OS processes, I will discuss in another blogpost.