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

Typical virtual memory layout, Using pages makes it easier to manage the wh...

Using pages makes it easier to manage the whole memory, avoiding excessive fragmentation and waste. As an analogy, think of Tetris, but with only square blocks: it is relatively ea

What is the design issues involved in segmentation?, SEGMENTATION HARDWARE ...

SEGMENTATION HARDWARE An execution to map two-dimensional user-defined addresses into one-dimensional physical addresses. This mapping is affected by means of segment table. Ev

Explain fixed partitioning in memory management, FIXED PARTITIONING Us...

FIXED PARTITIONING Using fixed partitioning we are able to allocate the memory Here we are dividing the memory into a few fixed partitions.Every partition may not be of the si

Explain the resource ownership and control, Explain the Resource Ownership ...

Explain the Resource Ownership and Control Operating systems are required to handle many different types of resources. CPU , memory, and I/O devices  are some of the varied sys

Producer - consumer system, In this exercise we are going to use  pthread()...

In this exercise we are going to use  pthread()to simulate the dynamics between a warehouse, factory and retail. The factory produces product by using parts supplied by the warehou

Define server processing with queues, Define Server Processing with Queues ...

Define Server Processing with Queues The efficient server processing of client request is essential for optimized client- server applications. This process is greatly enhanced

Explain the threadswitchwithdelay function used in netware, Explain the Thr...

Explain the ThreadSwitchWithDelay Function used in Netware ThreadSwitchWithDelay( )   This command is used when threads are waiting for an event or resource but don't want t

Draw and r chart and an x-bar chart, Thermostats are subjected to rigorous ...

Thermostats are subjected to rigorous testing before they are shipped to air conditioning technicians around the world. Results from the last five samples are shown in the table. D

Performance of job scheduling strategies, Performance of Job Scheduling  St...

Performance of Job Scheduling  Strategies In this project you will investigate the performance of Job Scheduling strategies, Memory Allocation strategies and a CPU Scheduling s

Objective, what are the objective of operating system assignment

what are the objective of operating system assignment

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