Problem of unbalanced loads, Operating System

Assignment Help:

Present your own fully documented and tested programming example illustrating the problem of unbalanced loads. Describe the use of OpenMP's scheduler as a means of mitigating this problem.

The below example shows a number of tasks that all update a global counter. Since threads share the same memory space, they indeed see and update the same memory location. The code returns a false result because updating the variable is  much quicker than creating the thread as on a multicore processor the chance of errors will greatly increase. If we artificially increase the time for the update, we will no longer get the right result. All threads read out the value of sum, wait a while (presumably calculating something) and then update.

#include

#include

#include "pthread.h"

int sum=0;

void adder() {

int sum = 0;

int t = sum; sleep(1); sum = t+1;

return;

}

#define NTHREADS 50

int main() {

int i;

pthread_t threads[NTHREADS];

printf("forking\n");

for (i=0; i

if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1;

printf("joining\n");

for (i=0; i

{

if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1;

printf("Sum computed: %d\n",sum);

}

return 0;

}

The use of OpenMP is the parallel loop. Here, all iterations can be executed independently and in any order. The pragma CPP directive then conveys this fact to the compiler. A sequential code can be easily parallelized this way.

#include 
#include 
#include "pthread.h"
int sum=0;
void adder() {
int sum = 0;
int t = sum; sleep(1); sum = t+1;
return;
}
#define NTHREADS 50
int main() {
int i;
pthread_t threads[NTHREADS];
printf("forking\n");
#pragma omp for
for (i=0; i
if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1;
}
printf("joining\n");
for (i=0; i
{
if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1;
printf("Sum computed: %d\n",sum);
}
return 0;
}

Related Discussions:- Problem of unbalanced loads

Difference between two tier and three tier architectures, Question: a) ...

Question: a) Illustrate with the help of a diagram, the difference between two tier and three tier architectures. b) Explain in what kind of environment, a peer to peer envi

Operational management, explain the link between operations management and ...

explain the link between operations management and strategic planning of daily goods shop

Paging, Paging full question

Paging full question

Describe the file system architecture, Describe the file system architectur...

Describe the file system architecture. File System Architecture contains the subsequent components:- Device Driver 1 Device Driver 2 Device Driver 3 Basic fi

General graph directory system in shell sort, we need an information about ...

we need an information about the different graph directory systems in detail by using shell sort . we also application part of directory systems in practical life. please help us i

Describe demand-paged environment, Q. Which of the subsequent programming ...

Q. Which of the subsequent programming techniques and structures are good for a demand-paged environment? Which aren't good? Describe your answers. a. Stack b. Hashed symbol

Producer - consumer synchronization, This assignment is based on Programmin...

This assignment is based on Programming Project 6.40 in Silbershatz. Implement the ProducerXConsumer program according to the instructions for Project 6.40 for both Linux and Win32

Multiprogramming, how response times are reduced by allowing time sharing o...

how response times are reduced by allowing time sharing on top of multiprogramming

What is the purpose of the global catalog, Question: (a) i. Consider A...

Question: (a) i. Consider Active Directory as a database, then for each type and new class of objects, what is created? ii. What is the purpose of the global catalog? ii

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd