Question

File input.txt contains 100,000 numbers separated by new line. 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.

Link to input: https://learn-us-east-1-prod-fleet01-xythos.s3.us-east-1.amazonaws.com/5b5739b6d55fd/3861301?response-content-disposition=inline%3B%20filename%2A%3DUTF-8%27%27input%25281%2529.txt&response-content-type=text%2Fplain&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20190317T013820Z&X-Amz-SignedHeaders=host&X-Amz-Expires=21600&X-Amz-Credential=AKIAIBGJ7RCS23L3LEJQ%2F20190317%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=8b1d2221f602a9dcc7b39390663d957f4fdc29f13dcf0e31e5ec15f1566b1907

Answer 1

#include <bits/stdc++.h>
using namespace std;
#define NUMBER_OF_THREADS 10
#define TOTAL_NUMBERS 100000
int arr[TOTAL_NUMBERS];
int sum[NUMBER_OF_THREADS];
int thread_number=0;

void * find_sum(void* arg)
{
int i,j,k;
int start=(thread_number*TOTAL_NUMBERS)/NUMBER_OF_THREADS;
int en=((thread_number+1)*TOTAL_NUMBERS)/NUMBER_OF_THREADS;
for(i=start; i<en;i++)
{
sum[thread_number]+=arr[i];
}
thread_number++;
}

int main()
{
ifstream infile("sample.txt");
int n=0,number,i,j;
while(infile>>number)
{
arr[n++]=number;
}
pthread_t T[10];

// creating the threads
for(i=0;i<10;i++)
{
pthread_create(&T[i], NULL, find_sum, (void*)NULL);
}

for (j = 0; j < 10 ; j++)
{
pthread_join(T[j], NULL);
}

int answer = 0;
for (int i = 0; i < NUMBER_OF_THREADS; i++)
{
answer+= sum[i];
}

cout<<"Total sum is "<<answer;
return 0;
}