double omp_get_wtime();

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

/**
 * @brief Illustrates how to measure time using walltime.
 * @details This code waits for a number of seconds given, by having a loop that
 * checks how many seconds elapsed since it started, and keeps looping until
 * enough seconds have passed by.
 **/
int main(int argc, char* argv[])
{
    // Time before the loop began
    double start_time;
    // Time right now
    double current_time;
    // Elapsed time since beginning of loop
    double elapsed_time;
    // Number of seconds to wait
    double to_wait = 3;

    // Initialise the start time
    start_time = omp_get_wtime();
    // Initialise the end time
    current_time = omp_get_wtime();
    // Initialise the elapsed time
    elapsed_time = current_time - start_time;

    // As long as fewer than "to_wait" seconds elapsed, keep looping
    while(elapsed_time < to_wait)
    {
        // Get the new time
        current_time = omp_get_wtime();
        // Update the elapsed time
        elapsed_time = current_time - start_time;
    }

    printf("%f seconds have elapsed.\n", elapsed_time);

    return EXIT_SUCCESS;
}