Question

Exercise 4 – Passing an argument to a new thread and reporting on execution times=====================================================================

Here are some miscellaneous items on threads and resource usage times. This is a very short exercise to learn how to pass an argument to a thread’s start function.

Write a program called threadArgA.c that simply does the following:

1. Pass a simple integer to a thread’s start function at thread creation time.
2. ii) The thread function will assign this argument as variable int i (just like the example in the notes) and use the variable to iterate something for i times, such as the following trivial code:

while ( i > 0) { printf ("Integer i has the value %d \n", i ); i--; }

3. The thread then exits

Now, for a final step. Before your main() function finishes it will find out how much CPU processing time was used in user space and kernel space while threadArgA was running. To achieve this use relevant code from the example cputime.c below. Now, suggest and write a fragment of code that is more interesting than the while() statement above to demonstrate use of processing time etc.

// cputime.c
// Small demo to show usage of getrusage() to measure CPU time
// DH 19/Sept/2012 ver 0.0.2
//////////////////////////////////////////////////////////////////
#include<stdio.h>
#include<stdlib.h>
#include<sys/time.h>
#include<sys/resource.h>
#include <unistd.h>
// Declare ru as a struct rusage;
struct rusage ru;
int main(void) {
//////////////////////////////////////////////////////////////////
// Just some silly code to use up a few seconds of CPU time
printf ("\n A dummy program is running .... PLEASE WAIT!!! \n\n");
float y;
int x,v;
for (v=1;v<500;v++){
for (x=1;x<1000000;x++){
y++;
}
}
//////////////////////////////////////////////////////////////////
getrusage(RUSAGE_SELF, &ru);
printf ("Usage results for this program are:\n\n");
printf("User space CPU time used: %6lu %6lu\n", ru.ru_utime.tv_sec, ru.ru_utime.tv_usec );
printf("Kernel CPU time used: %6lu %6lu\n", ru.ru_stime.tv_sec, ru.ru_stime.tv_usec );
return 0;
}

Answer 1

threadArgA.c

************************

#include<stdio.h>

#include<stdlib.h>

#include<sys/time.h>

#include<sys/resource.h>

#include<unistd.h>

#include<pthread.h>

struct rusage ru;

//The Function to be executed by thread

void *myThread(void *vargp)

{

//Store the value argument passed to this thread

int *myid = (int *)vargp;

//Print the argument

printf("Thread ID :%d\n", *myid);

}

int main(void)

{

int i;

pthread_t tid;

for(i = 0; i < 1; i++)

{

//Create the thread

pthread_create(&tid, NULL, myThread, (void *)&tid);

}

while( i > 0)

{

printf(" Integer i has the value %d\n", i);

i--;

}

getrusage(RUSAGE_SELF, &ru);

printf(" Usage results for this program are : \n\n");

printf(" User space CPU time used : %6lu %6lu\n", ru.ru_utime.tv_sec, ru.ru_utime.tv_usec);

printf("Kernel CPU time used : %6lu %6lu\n", ru.ru_stime.tv_sec, ru.ru_stime.tv_usec);

pthread_exit(NULL);

return 0;

}