Hey everyone, I am just starting to learn about threads, and I am trying to write a thread to compute fibonacci and return an indicated fibonacci number. I have to use pthread_join to wait and collect the returned value, and then print it. Hereis what I have so far, but I am stuck, it keeps giving me the error " fibon.c: (.text+0x65): undefined reference to `fibonacci' collect2: ld returned 1 exit status" Please help me! Code: #include <pthread.h> #include <stdio.h> /* compute sucessive fibonnaci numbers.*/ void* fibonacci(void* arg); main() { pthread_t thread; int num1 = 0; int num2 = 1;; int ans; int which_fibo; int counter, numPrint; numPrint = 10; for(counter= 0; counter < numPrint; ++counter){ ans = (num1 + num2); num1 = num2; num2 = ans; } /* start the computing thread up to the number you want to return*/ pthread_create(&thread, NULL, &fibonacci, (void*)&which_fibo); /* wait for the fibonacci thread to complete */ pthread_join(thread, (void*)&ans); /* print the number in the position requested */ printf("the number is %d.\n",which_fibo, ans); }

Some progress...Now my program is printing 2 positions ahead. For exemplo: 0 1 1 2 3 5 8 13 If I select to print position 3, the result would be 3. If I select to print position 4, the result would be 5.ow How can I fix this problem, and how can I return the value if the position selected is 1 or 2? #include <pthread.h> #include <stdio.h> /* compute sucessive fibonnaci numbers.*/ void* fibonacci(void* arg){ int num1 = 1; int num2 = 1;; int ans; int maxfibo=10; int n = *((int*) arg); int is_num = 1; int counter; for(counter= 0; counter < (maxfibo-2); ++counter){ ans = (num1 + num2); num1 = num2; num2 = ans; if (is_num) { if (--n==0) return (void*) ans; } } } int main () { pthread_t thread; int which_fibo = 5; int number; /* start the computing thread up to the number you want to return*/ pthread_create(&thread, NULL, &fibonacci, (void*)&which_fibo); /* wait for the fibonacci thread to complete */ pthread_join(thread, (void*)&number); /* print the number in the position requested */ printf("The number is %d.\n", number); return 0; }