For the program given written in C, collect the final result of adding 1 to 2 billion by using shared memory among 4 processes.

• You can refer to the sample code (ipcsm.c) discussed in class for reference.
• Step 1: Create a shared memory space (4*8=32 bytes) for holding 4 partial sum (long)
• Step 2: Every process calculates the partial sum and writes the result on a location on the created shared memory without conflicting with each other.
• Step 3: After all the processes finished their calculation, the master process collects all the partial results and deliver the final result to the terminal.

Program given:

#include

#include

#include

#include

#include

void sum1b(); //sum 1 to 1 billion

void sum2b(); //sum 1 billion to 2 billion

void sum3b(); //sum 1 to 1 billion

void sum4b(); //sum 1 billion to 2 billion

int main(){

int status;

pid_t pid1 = fork();

//timer

struct timeval start, end;

long mtime, seconds, useconds;

gettimeofday(&start, NULL); //timer

if(pid1 < 0){ //fork failed

fprintf(stderr, "Fork Failed!");

return 1;

}else if(pid1 == 0){ //child process

pid_t pid2 = fork();

if(pid2==0){

pid_t pid3 = fork();

if(pid3==0){

sum4b();

}else{

sum3b();

wait(NULL);

}

}else{

sum2b();

wait(NULL);

}

}else{ //parent process

sum1b();

wait(NULL);

gettimeofday(&end, NULL); //timer

//timer

seconds = end.tv_sec - start.tv_sec;

useconds = end.tv_usec - start.tv_usec;

mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5;

printf("Elapsed time: %ld milliseconds on pid=%d ", mtime, pid1);

}

return 0;

}

void sum1b(){

long sum =0;

for(int i=1;i<500000000;i++){

sum += i;

}

printf("The sum of 1 to 0.5b is: %ld ", sum);

}

void sum2b(){

long sum =0;

for(int i=500000000;i<1000000000;i++){

sum += i;

}

printf("The sum of 0.5b to 1b is: %ld ", sum);

}

void sum3b(){

long sum =0;

for(int i=1000000000;i<1500000000;i++){

sum += i;

}

printf("The sum of 1 to 1.5b is: %ld ", sum);

}

void sum4b(){

long sum =0;

for(int i=1500000000;i<2000000000;i++){

sum += i;

}

printf("The sum of 1.5b to 2b is: %ld ", sum);

}

ipcsm.c:

#include

#include

#include

#include

#include

#include

#define SHM_SIZE 1024 /* make it a 1K shared memory segment */

//display sharedMemory: ipcs -m

//remove sharedMemory: ipcrm -M 0x0000162e

int main(int argc, char *argv[])

{

key_t key;

int shmid;

char *data;

int mode;

if (argc > 2) {

fprintf(stderr, "usage: shmdemo [data_to_write] ");

exit(1);

}

/* make the key: */

if ((key = ftok("ipcsm.c", 'R')) == -1) /*Here the file must exist */

{

perror("ftok");

exit(1);

}

/* create the segment: */

if ((shmid = shmget(key, SHM_SIZE, 0644 | IPC_CREAT)) == -1) {

perror("shmget");

exit(1);

}

/* attach to the segment to get a pointer to it: */

data = shmat(shmid, (void *)0, 0);

if (data == (char *)(-1)) {

perror("shmat");

exit(1);

}

/* read or modify the segment, based on the command line: */

if (argc == 2) {

printf("writing to segment: \"%s\" ", argv[1]);

strncpy(data, argv[1], SHM_SIZE);

} else

printf("segment contains: \"%s\" ", data);

/* detach from the segment: */

if (shmdt(data) == -1) {

perror("shmdt");

exit(1);

}

return 0;

}