Question

Here is my fibonacci code using pthreads. When I run the code, I am asked for a number; however, when I enter in a number, I get my error message of "invalid character." ALSO, if I enter "55" as a number, my code automatically terminates to 0. I copied my code below. PLEASE HELP WITH THE ERROR!!!

#include
#include
#include
#include
#include

int shared_data[10000];

void *fibonacci_thread(void* params);
void parent(int* numbers);

int main() {

   int numbers = 0; //user input.

   pthread_t child; // create thread
   pthread_attr_t attr;
   pthread_attr_init(&attr);

   parent(&numbers); // get user input then start separate thread.
   pthread_create(&child, &attr, fibonacci_thread, (void*) &numbers); //starts fibonacci thread
   pthread_join(child, NULL); //waits for thread to finish

   //output to command prompt after thread finishes.
   for(int i = 0; i <= shared_data[i]; i++) {
       printf("%d",shared_data[i]);
   }

   return 0;
}

void *fibonacci_thread(void* params) {

   int fib0 = 0, fib1 = 1, next = 0;
   int *pointer;
   pointer = (int*) params;
   int total = *pointer;

   for (int i = 0 ; i < total; i++ ) {
if ( i <= 1 )
next = i;
else {
next = fib0 + fib1;
fib0 = fib1;
fib1 = next;
}
   next = shared_data[i]; //store to shared_data array
   }
   //pthread_exit(0);
   return NULL;
}

void parent(int* numbers) {
   std::cout<<"Enter in a number to generate the Fibonacci sequence: ";
   std::cin>>*numbers;

   while(isdigit(*numbers) != true) {
       std::cout<<"Invalid character, please enter in a number: ";
       std::cin>>*numbers;
   }

   return;
}

here is the error below:

student@tuffix-vm:~$ cd CPSC-351-Project2-Fall2020
student@tuffix-vm:~/CPSC-351-Project2-Fall2020$ g++ -pthread fibonacci.cpp -o fibonacci
student@tuffix-vm:~/CPSC-351-Project2-Fall2020$ ./fibonacci
Enter in a number to generate the Fibonacci sequence: 2
Invalid character, please enter in a number: 3
Invalid character, please enter in a number: 4
Invalid character, please enter in a number: 5
Invalid character, please enter in a number: 6
Invalid character, please enter in a number: 7
Invalid character, please enter in a number: 8
Invalid character, please enter in a number: 9
Invalid character, please enter in a number: 55
student@tuffix-vm:~/CPSC-351-Project2-Fall2020$

Answer 1

Please look at my code and in case of indentation issues check the screenshots.

--------------main.cpp---------------

#include <pthread.h>
#include <iostream>
#include <stdlib.h>
#include <string>

int shared_data[10000];

void *fibonacci_thread(void *params);
void parent(int *numbers);
bool isNumber(std::string str);

int main()
{
   int numbers = 0;   //user input.

   pthread_t child;   // create thread
   pthread_attr_t attr;
   pthread_attr_init(&attr);

   parent(&numbers);   // get user input then start separate thread.
   pthread_create(&child, &attr, fibonacci_thread, (void*) &numbers);   //starts fibonacci thread
   pthread_join(child, NULL);   //waits for thread to finish

   //output to command prompt after thread finishes.
   for (int i = 0; i < numbers; i++)
   {
       printf("%d ", shared_data[i]);   //prints the array written by the thread
   }
   std::cout << "\n";
   return 0;
}

void *fibonacci_thread(void *params)
{

   int fib0 = 0, fib1 = 1, next = 0;
   int *pointer;
   pointer = (int*) params;
   int total = *pointer;

   for (int i = 0; i < total; i++)   //loop to generate next fibonacci number
   {
       if (i <= 1)
           next = i;
       else
       {
           next = fib0 + fib1;
           fib0 = fib1;
           fib1 = next;
       }
       shared_data[i] = next;   //store to shared_data array
   }
   //pthread_exit(0);
   return NULL;
}

void parent(int *numbers)
{
   std::string input;
   std::cout << "Enter in a number to generate the Fibonacci sequence: ";
   std::cin >> input;       //read the input as a string

   while (isNumber(input) != true)   //check if input is a number
   {
       std::cout << "Invalid input, please enter in a number: ";
       std::cin >> input;           //if not a number ask for another input
   }
   *numbers = atoi(input.c_str());   //if input was a number, convert it from string to integer

   return;
}

bool isNumber(std::string str)   //this function takes a string and checks if it is a positive number
{
   for (int i = 0; i < str.length(); i++)
   {
       if (!isdigit(str[i]))   //is digit is used to check if one character is a digit
           return false;   //when even one character is not a digit, return false
   }
   return true;   //if all characters are digits return true
}

----------Screenshots--------------

----------Output--------------

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