Description

Experiment 1. Thread and Process Creation

Study the programs thr_create.c and fork.c. These programs measure the average time to

create a thread using thr_create() and to create a process using fork(). Compile and

execute the programs. What do you conclude from this experiment? Describe the reasons

for the difference in timings.

• Experiment 2. Processes vs Threads

Study the two programs thr_shared.c and proc_shared.c. These programs are identical

except that one uses threads and the other uses processes. Compile and execute the

programs. What do you conclude from this second experiment? Explain the reason for the

difference in behavior.

• Experiment 3: The Update Problem

Study the programs shared_data.c and SharedData.java. In these examples, multiple

threads are both updating (i.e., modifying) a shared variable. Compile and execute both.

Are the programs behaving "correctly"? What do you conclude from this experiment?

README Instructions

• Run the program on Linux platform.

• To compile and run a C program (e.g., thr_create.c):

gcc -o thr_create thr_create.c -lpthread

thr_create

• To build and run a classfile from the java code:

javac SharedData.java

java SharedData

thr_create.c

#include <sys/time.h>

#include <stdio.h>

#include <pthread.h>

#include <errno.h>

main()

{

struct timeval start,end;

long forktime;

double avgtime;

pthread_t last_thread;

int i;

int iters = 250;

void *null_proc();

gettimeofday(&start,NULL);

for (i = 0; i < iters - 1; i++) /* create (iters-1) threads */

pthread_create(&last_thread,NULL,null_proc,NULL);

pthread_create(&last_thread,NULL,null_proc,NULL); /* create last thread */

gettimeofday(&end,NULL);

pthread_join(last_thread, NULL); /* wait for last thread */

forktime = (end.tv_sec - start.tv_sec)*1000000 +

(end.tv_usec - start.tv_usec);

avgtime = (double)forktime/(double)iters;

printf("Avg thr_create time = %f microsec\n", avgtime);

}

void *null_proc()

{}

fork.c

#include <sys/time.h>

#include <stdio.h>

#include <errno.h>

main()

{

int pid;

struct timeval start,end;

int i;

long forktime;

double avgtime;

int iters = 250;

int status;

gettimeofday(&start,NULL);

for (i = 0; i < iters; i++) /* create iters processes */

{

if ((pid = fork()) == 0) /* child process */

{

null_proc();

exit(1);

}

else if (pid == -1) /* error */

{

printf("error %d\n",errno);

exit(-1);

}

else /* parent process */

continue;

}

/* only parent process reaches this point */

gettimeofday(&end,NULL);

for ( i = 0; i < iters; i++) /* have to do a wait for each child */

wait(&status);

forktime = (end.tv_sec - start.tv_sec)*1000000 +

(end.tv_usec - start.tv_usec);

avgtime = (double)forktime/(double)iters;

printf("Avg fork time =%f microsec\n", avgtime);

}

null_proc()

{

}

thr_shared.c

#include <sys/time.h>

#include <stdio.h>

#include <pthread.h>

#include <unistd.h>

#include <stdlib.h>

void *proc();

int shared_number;

main()

{

int i;

pthread_t new_thread;

int sleep_time;

int seed;

shared_number = 1;

printf("Enter a positive integer for seed: ");

scanf("%d",&seed);

srand48(seed); /* initialize seed of random number stream */

/* thr_create(NULL,0,proc,NULL,0,&new_thread);*/

pthread_create(&new_thread,NULL,proc,NULL);

/* create new thread */

for (i = 0; i < 50; i++)

{

printf("MAIN THREAD: i = %d, shared_number = %d\n",i,shared_number);

sleep_time = 100000.0*drand48(); /* generate random sleep time */

printf("sleep time = %d microseconds\n",sleep_time);

usleep(sleep_time);

shared_number = shared_number + 2;

}

pthread_join(new_thread,NULL);

printf("MAIN THREAD: DONE\n");

}

void *proc()

{

int i = 0;

int DONE;

DONE = 0;

while (!DONE)

{

i++;

if (i%10000 == 0)

printf("CHILD THREAD: i = %d,shared_number = %d\n",i,shared_number);

if (i > 5000000)

DONE = 1;