/*NOTES:
	//  means single line comment in c/C++
	$   means right after it the command line starts
	#	to warn the compiler for adding aditional files or special events

What is the program for?
	To show difference between private() and firstprivate() OpenMP clauses.
	C/C++ allows you to declare a varable and initialize them value.
 
	For Example: int moon_distance = 238900;
	
	So whenever a function uses the variable moon_distance, it will use it 
	with the value 238900. However, in OpenMP parallel region, private varables are
	not intialized. (Why good question for OpenMP). So if you wanted to make an 
	initialized variable private to each thread. Then you have to tell it explicitly
	with the use of firstprivate() clause. Compiling this code on Blue Waters may 
    give you some warning also, telling you to change the moon_distance from private
    to firstprivate variable.

How to Compile:
    $ gcc -fopenmp omp_var_initialization.c -o omp_var_initialization

How to Setup Runtime Environment:
    $ export OMP_NUM_THREADS=4

How to Run:
    $ ./omp_var_initialization
Output:
This value is the when use private() clause
thread 1: moon_distance = -22032 
thread 0: moon_distance = 0 
thread 2: moon_distance = -22032 
thread 3: moon_distance = -22032 

This is the value using firstprivate() clause
thread 0: moon_distance = 238900 
thread 1: moon_distance = 238900 
thread 2: moon_distance = 238900 
thread 3: moon_distance = 238900 
Actual initialization is: moon_distance = 238900
*/

#include <stdio.h>
#include <omp.h>
int main (void)
{
    int moon_distance = 238900;
    int n_moon_distance = 0;
    
    printf(" \n");
    printf("This value is the when use private() clause\n");

#pragma omp parallel private(moon_distance)
    {   
        printf("thread %d: moon_distance = %d \n", omp_get_thread_num(), moon_distance);
    }  
    printf(" \n");
	printf("This value is the when use firstprivate() clause\n");

#pragma omp parallel firstprivate(moon_distance)
	{
        printf("thread %d: moon_distance = %d \n", omp_get_thread_num(), moon_distance);
	}
	printf(" \n");
    printf("Actual initialization is: moon_distance = %d \n", moon_distance);

#pragma omp parallel firstprivate(moon_distance)
    {
    //#pragma omp lastprivate(n_moon_distance)
    
        moon_distance = moon_distance+300000;
        printf("thread %d: moon_distance = %d And the new distance is %d \n", omp_get_thread_num(), moon_distance, moon_distance);
    }
    printf(" \n");

    return 0;
}