Question

write C program to create 4 threads for summing the numbers between 1 and 40 where the first thread computes the sum between 1 and 10; the second thread computes the sum between 11 and 20; the third thread computes the sum between 21 and 30; and the fourth thread compute the sum between 31 and 40. The output should be similar to the following.

The sum from 1 to 10 = 55

The sum from 11 to 20 = 155

The sum from 31 to 40 = 355

The sum from 21 to 30 = 255

Thread 0: 55

Thread 1: 155

Thread 2: 255

Thread 3: 355

Total = 820

All programs must be run under the department’s Unix server.

To compile your code in Unix, you need to include pthread library as follows >> gcc Thread.c –pthread

Answer 1

Solution:

Calculating sum using Arithmatic Progression.

Sum of n terms in AP = (n/2)*(2*a + (n-1)*d)

here n = 10 , a is the start value , d = 1

On simplification............

Sum = 5 * ( 2*a + 9 )

Look at the code and comments for better understanding......

Screenshot of the code:

Output:

Code to copy:

#include<stdio.h>
#include<pthread.h>
#include<stdlib.h>
void *calculateSum(void *args)
{
        //getting the start value
        int start=*((int *)args);
        int *sum=(int *)malloc(sizeof(int));
        //calculating the sum stating with value start
        // using the formula sum=5*(2*start+9)
        *sum = 5*(start*2+9);
        printf("The sum from %d to %d = %d\n",start,start+9,*sum);
        //returning the sum
        pthread_exit(sum);
}
int main()
{
        //creating 4 thread variables
        pthread_t t1,t2,t3,t4;
        //assingning the start value
        int start1=1,start2=11,start3=21,start4=31;
        //creating 4 threads
        pthread_create(&t1,NULL,calculateSum,(void *)&start1);
        pthread_create(&t2,NULL,calculateSum,(void *)&start2);
        pthread_create(&t3,NULL,calculateSum,(void *)&start3);
        pthread_create(&t4,NULL,calculateSum,(void *)&start4);
        //getting the sum value from thread and storing it in ret variable
        void *ret_value;
        pthread_join(t1,&ret_value);
        int ret1=*((int *)ret_value);
        pthread_join(t2,&ret_value);
        int ret2=*((int *)ret_value);
        pthread_join(t3,&ret_value);
        int ret3=*((int *)ret_value);
        pthread_join(t4,&ret_value);
        int ret4=*((int *)ret_value);
        //printing the thread return values
        printf("Thread 0 :%d\n",ret1);
        printf("Thread 1 :%d\n",ret2);
        printf("Thread 2 :%d\n",ret3);
        printf("Thread 3 :%d\n",ret4);
        //calculatin total value
        int total_sum=ret1+ret2+ret3+ret4;
        printf("Total = %d\n",total_sum);
}

I hope this would help.........................:-))