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

Designing issues in a network -transparency, Transparency Users mus...

Transparency Users must be able to access remote resources as though these resources were local. Transparency should as well promote user mobility. Users must be allowed

Long term scheduler, Long term scheduler calculates which processes are a...

Long term scheduler calculates which processes are admitted to the machine for processing. It accepts the degree of multiprogramming. Once accepted, a job converts a process.

Explain about spooling, Q. Explain about Spooling? Acronym for simu...

Q. Explain about Spooling? Acronym for simultaneous peripheral operations on line. Spooling denotes to putting jobs in a buffer, a special area in memory or on a disk where

What are the three main activities of an operating system, What are the thr...

What are the three main activities of an operating system in regard to memory management? Keep track of which parts of memory are now being used and by whom. Decide which pr

Difference between message passing and shared memory, Problem: a) To en...

Problem: a) To ensure proper operation, the operating system and all the other programs must be protected from any malfunctioning program. Describe a mechanism which is impleme

Define dynamic loading, Define dynamic loading. To obtain better memory...

Define dynamic loading. To obtain better memory-space utilization dynamic loading is used. With dynamic loading, a routine is not loaded until it is called. All routines are ke

Monolithic, What is monolithic and its diagram

What is monolithic and its diagram

Define state that process must obtain all resources it needs, Before procee...

Before proceeding with its execution, every process must obtain all the resources it needs is called Hold and wait

Operating system strectures, with the aid of diagrams describe the followin...

with the aid of diagrams describe the following os structures monolithic , layered, client server

Explain what type of group scope you will use, Question: (a) The actual...

Question: (a) The actual use and scope groups depend on the mode in which a domain is running. There are two domain modes in which you can run a Windows 2000 domain. List and d

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