Data races, critical sections, processor loading, Operating System

Assignment Help:

Research the phenomenon of data races. Give an example of how an unprotected data race can give rise to data inconsistency. How do OpenMP and Cilk resolve this problem?

Data race is that situation or condition in which multiple threads, without intervening synchronization, try to access the same memory location, with at least one thread performing a write operation. For eg. many data races occur on numerical algorithms owing to chaotic relaxation and asynchronous iterative methods. Also, there are systems where synchronized threads or processes maintain probabilities with best-estimate-matrix and may race with one other to provide updates.This is usually described in higher-level language specs by the phrase: "undefined behavior." A data race could legitimately reprogram the BIOS delete data from the disk and may also stop the processor's fan leading to a multi-core meltdown. 

example code:

 

int checker = 0;

int counts = 0;

Lock lock;

 

bool TryEnter() {

    if (checker == /* get thread id */) {

        counts += 1;

        return true;

    }

 

    if (lock.TryEnter()) {

        checker = /* get thread id */;

        return true;

    }

    return false;

}

 

void Exit() {

    if (counts != 0) {

        counts -= 1;

        return;

    }

    checker = 0;

    lock.Exit();

}

 

the compiler or the processor may “optimize” this program as:

 

void Exit() {

    if (counts != 0) {

        counts -= 1;

        return;

    }

    checker = 42;

    checker = 0;

    lock.Exit();

} 

The effect of this is perhaps not observable in the current thread, nor is it observable by other threads in the absence of data races. Here, the unfortunate thread whose ID is 42 might observe this value and take the ignite the mistake. 

OpenMP and Cilk resolve data racing through a technique known as Data parallelism.It focuses on distributing the data across different parallel computing nodes. This is achieved when each processor performs the same task on different pieces of distributed data. In some situations, a single execution thread controls operations on all pieces of data. In others, individual threads control the operation, but they execute the same code.


Related Discussions:- Data races, critical sections, processor loading

Is disk scheduling except fcfs scheduling, Q. Is disk scheduling except FC...

Q. Is disk scheduling except FCFS scheduling useful in a single-user environment? describe your answer. Answer: In a single-user environment the I/O queue typically is empty.

Explain internal fragmentation, Explain internal fragmentation The Inter...

Explain internal fragmentation The Internal fragmentation signifies to the result of reserving a piece of space without ever intending to use it. This space is wasted that this

Linux, write a linux command to display lines from 25 - 45 of directory "/e...

write a linux command to display lines from 25 - 45 of directory "/edc/password" write a linux command to display directory in /edc

What does verification represent, What does Verification represent? Ver...

What does Verification represent? Verification shows the set of activities that are carried out to confirm that the software correctly executes the specific functionality.

Semaphore examples, Ok so i think i got this right by not 100% on this. wha...

Ok so i think i got this right by not 100% on this. what I want to figure out is if there are x visitors that can line up for a ride but only 1 passenger can get on the ride at a t

Operating system as user interface, Q. Operating System as User Interface? ...

Q. Operating System as User Interface? • Every general purpose computer comprises the operating system, hardware, system programs and application programs. The hardware compris

Memory management, what is segmentation as it refers to operating system

what is segmentation as it refers to operating system

Explain structure, Explain Structure The Grammar for programming langua...

Explain Structure The Grammar for programming language is a formal description of Structure

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