This program uses a thread to generate a summation of 1 to n, that is, 1+2+3.. +n. Let us modify this code (consum.c) as follows.

Instead of one thread summing all numbers from 1 to n, let us split the task into two halves and assign each half to two separate threads (that means you need to create two threads). One thread sums from 1 to n/2 (assume n is even), and the other thread sums from n/2 + 1 to n. Once the two children threads join, the parent/main program sums the two results to obtain the overall summation and prints the summation.

Compile your program using gcc -lpthread and run on the Linux VM

#include #include #include

int sum; /* this data is shared by the thread(s) */

void *runner(void *param); /* the thread */

int main(int argc, char *argv[]) { pthread_t tid; /* the thread identifier */ pthread_attr_t attr; /* set of attributes for the thread */

if (argc != 2) { fprintf(stderr,"usage: a.out "); /*exit(1);*/ return -1; }

if (atoi(argv[1]) < 0) { fprintf(stderr,"Argument %d must be non-negative ",atoi(argv[1])); /*exit(1);*/ return -1; }

/* get the default attributes */ pthread_attr_init(&attr);

/* create the thread */ pthread_create(&tid,&attr,runner,argv[1]);

/* now wait for the thread to exit */ pthread_join(tid,NULL);

printf("sum = %d ",sum); }

/** * The thread will begin control in this function */ void *runner(void *param) { int i, upper = atoi(param); sum = 0;

if (upper > 0) { for (i = 1; i <= upper; i++) sum += i; }

pthread_exit(0); }