Question

1. File input.txt contains 100,000 numbers separated by new line. Do the following: 1.1 Write a C++ program to compute the summation of these 100,000 numbers using single thread. 1.2 Write a C++ program to compute the summation of these 100,000 numbers using 10 threads, meaning each thread compute 10,000 summations and the main thread sum the result of the 10 threads. 1.3 Using the time syscall to compare the time spent for 1.1 and 1.2 Source code of two programs and a short report on to answer the following question: 1. What is the run time for 1.1? 2. What is the run time for 1.2? 3. Is there a run time difference and why?

Answer 1

#include <pthread.h>
#include <iostream>
#include <cstdlib>

using namespace std;

// The adder thread that will add the number from 1 to n
void *adder(void * number);

// The sum variable that will be updated by all threads
unsigned long sum;

int main(int argc, char *argv[])
{
    if (argc != 2) {
        cerr << "Usage: sum <integer value>" << endl;
        exit(1);
    }

    unsigned long number = atol(argv[1]);
    if (number < 0) {
        cerr << "Argument " << number << " must be non-negative." << endl;
        exit(1);
    }
    
    pthread_t tid; // the thread identifierier
    pthread_attr_t attr; // set of attributes for the thread
    
    // get the default attributes
    pthread_attr_init(&attr);

    // create the thread
    pthread_create(&tid,&attr,adder,(void *) number);
    
    // Wait for the thread to exit
    pthread_join(tid,NULL);
    
    cout << "Sum(" << 1 << ", " << number << ") = " << sum << endl;
    
    return 0;
}