A simple OpenMP example

/*
* SimpleForDirective.cpp
* F=OpenMpDemo && g++ -c $F.cpp -o $F.o -fopenmp -std=c++0x && g++ $F.o -o $F.exe -fopenmp && ./$F.exe
*/

#include <iostream>
#include <iterator>
#include <algorithm>
#include <vector>
#include <stdio.h>

using namespace std;

void sequential(int *a, int size, int *b)
{
    int i;
    for (i = 0; i < size; i++) {
        b[i] = a[i] * i;
    }
}

void parallel_for(int *a, int size, int *b)
{
#pragma omp parallel for
    for (int i = 0; i < size; i++) {
        b[i] = a[i] * i;
    }
}

void parallel_for_with_an_usage_error(int *a, int size, int *b)
{
    int j;
#pragma omp parallel for
    for (int i = 0; i < size; i++) {
        /*int*/ j = a[i]; //To be correct j should be declared here, in-loop to be private !
        j *= i;
        b[i] = j;
    }
}

#define SIZE 9999
//#define DUMP_ARRAY

int main(int ac, char** av)
{
    cout << "OpenMP Demo Simple For Directive and sharing example....." << endl;
    int a[SIZE]; int root = 1; generate(a, a+SIZE, [&root](){return ++root;});
    int b[SIZE]; fill(b, b+SIZE, 0);

    sequential(&a[0], SIZE, b);
#ifdef DUMP_ARRAY
    copy(b, b + SIZE, ostream_iterator<int>(cout, " ")), cout << endl;
#endif
    int reference[SIZE]; copy(b, b + SIZE, reference);

    /*parallel_for(&a[0], SIZE, b);
#ifdef DUMP_ARRAY
    copy(b, b + SIZE, ostream_iterator<int>(cout, " ")), cout << endl;
#endif
    //*/

    parallel_for_with_an_usage_error(&a[0], SIZE, b);
#ifdef DUMP_ARRAY
    copy(b, b + SIZE, ostream_iterator<int>(cout, " ")), cout << endl;
#endif
    //*/

    if(!equal(b, b+SIZE, reference)){
        cout << "error .... " << endl;
    } else {
        cout << "ok .... " << endl;
    }
    return 0;
}