Question

Read the following code, threaded recursive calculation of Fibonacci number of n:

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

void *fib(void *arg);

int main(int argc, char **argv){
    int n = atoi(argv[1]);

    printf("%d\n", (int)fib(n));
}

void *fib(void *arg){
    int n;
    pthread_t thread1;
    pthread_t thread2;
    void *a;
    void *b;
    int c;

    n = (int)arg;
    if (n <= 0) return 0;
    if (n == 1) return 1;
    pthread_create(&thread1, NULL, fib, n-1);
    pthread_create(&thread2, NULL, fib, n-2);

    pthread_join(thread1, &a);
    pthread_join(thread2, &b);

    c = (int)a + (int)b;
    return (c);
}

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Question: 1. Prove the number of threads created is at most 2ⁿ using a binary tree. (n = Fibonacci number)

2. Write a non-threaded recursive version of Fibonacci in C

Answer 1