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    /*
     * Parallel fibonacci.
     *
     * This is just a toy program to see how well the
     * underlying FJ framework supports extremely fine-grained
     * tasks.
     *
     * Written by G. Back for CS3214 Fall 2014.
     */
    #include <pthread.h>
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include <stdint.h>
    #include <unistd.h>
    #include <sys/time.h>
    #include <sys/resource.h>
    #include <time.h>
    
    #include "threadpool.h"
    #include "threadpool_lib.h"
    
    /* Data to be passed to callable. */
    struct problem_parameters {
        unsigned n;
    };
    
    static void *
    fibonacci(struct thread_pool * pool, void * _data)
    {
        struct problem_parameters * p = _data;
        if (p->n <= 1)
            return (void *) 1;
    
        struct problem_parameters left_half = { .n = p->n - 1 };
        struct problem_parameters right_half = { .n = p->n - 2 };
        struct future * f = thread_pool_submit(pool, fibonacci, &right_half);
        uintptr_t lresult = (uintptr_t) fibonacci(pool, &left_half);
        uintptr_t rresult = (uintptr_t) future_get(f);
        future_free(f);
        return (void *)(lresult + rresult);
    }
    
    static void usage(char *av0, int nthreads) {
        fprintf(stderr, "Usage: %s [-d <n>] [-n <n>] <N>\n"
                        " -n        number of threads in pool, default %d\n"
                        , av0, nthreads);
        exit(0);
    }
    
    int
    main(int ac, char *av[])
    {
        int nthreads = 4;
        int c;
        while ((c = getopt(ac, av, "n:h")) != EOF) {
            switch (c) {
            case 'n':
                nthreads = atoi(optarg);
                break;
            case 'h':
                usage(av[0], nthreads);
            }
        }
        if (optind == ac)
            usage(av[0], nthreads);
    
        int n = atoi(av[optind]);
        struct thread_pool * pool = thread_pool_new(nthreads);
    
        struct problem_parameters roottask = { .n = n };
    
        unsigned long long F[n+1];
        F[0] = F[1] = 1;
        int i;
        for (i = 2; i < n + 1; i++) {
            F[i] = F[i-1] + F[i-2];
        }
    
        printf("starting...\n");
        struct benchmark_data* bdata = start_benchmark();
        struct future *f = thread_pool_submit(pool, fibonacci, &roottask);
        unsigned long long Fvalue = (unsigned long long) future_get(f);
        stop_benchmark(bdata);
        future_free(f);
        if (Fvalue != F[n]) {
            printf("result %lld should be %lld\n", Fvalue, F[n]);
            abort();
        } else {
            printf("result ok.\n");
            report_benchmark_results(bdata);
        }
    
        thread_pool_shutdown_and_destroy(pool);
        return 0;
    }