Identifying parallelism, Operating System

Assignment Help:

Identifying parallelism

A formal way to identify parallelism in an activity is to draw a task dependence graph in a directed graph in which each vertex represents a task to be completed. An edge from vertex u to vertex means that task u must be completed before task v begins, so that task v "depends on" u. If there is no path from u to v, then the tasks are independent and may be performed concurrently. Consider the following problem: Alice is the leader of a crew of workers who maintain a large estate. There are four principal tasks: mowing the lawns, pruning the trees and hedges, repairing the fences, and inspecting the work to ensure it has all been done satisfactorily. Mowing must be completed before the work is inspected, as must the pruning and fence repair. The estate has a security system which must be switched off before work commences (i.e. before Alice and her team arrives), and switched on again after the team leaves.

  • Draw the dependence graph corresponding to the above problem, showing all the tasks involved. (In a project management plan, this scheme is often referred to as a "work breakdown structure").
  • Alice has 8 people in her crew, including herself. (The crew members are: Alice, Bert, Cressida, Dominic, Edgar, Frank, Gus and Harriet). Alice will be solely responsible for inspecting the work, but decides that she herself and three other people (Bert, Dominic and Gus) will mow the estate's four lawns (referred to as north, south, west and east lawns, each of which are of equal area), two other people (Cressida and Frank) will prune the trees, whilst Edgar and Harriet will repair the fences. Redraw the graph to show the allocation of the crew to particular tasks. (Hint: a single task in the original graph may be come multiple tasks in the revised version, each of which is performed by a particular person).
  • Alice is a fast worker, and can mow any of the lawns in one hour, as can Dominic. Frank and Gus can complete any of the manual tasks in two hours. Bert, Cressida, Edgar and Harriet take three hours to do their work. If the manual work starts at 10:00 a.m. in the morning, at what time scan Alice inspect the work? In your answer, refer to the dependence graph showing the allocation of crew to tasks.

Since mowing is done first and then all team members start the work simuntaneosly and Alice can only inspect after each has finished their task the time taken by the slowest team members will be seen here.

Harriert/Bert/Credessia and Edgar take 3 hrs each to complete their task.

The manual work starts at 10.00 AM so the inspection will start 3+3 =6 hrs after that.


Related Discussions:- Identifying parallelism

Mechanism for code and data sharing, Q. Consider a system in which a progr...

Q. Consider a system in which a program is able to be separated into two parts: code and data. The CPU recognizes whether it wants an instruction (instruction fetch) or data (data

Describe internal layout of the file system in windows 2000, Describe the i...

Describe the internal layout of the file system in windows 2000. The basic entity in NTFS is a volume and a volume is created by the Windows 2000 disk administrator utility and

Blocking locks, We have talked about blocking locks, which voluntarily yiel...

We have talked about blocking locks, which voluntarily yield, and spinlocks, which just spin until they acquire the lock. At ?rst, it seems like spinlocks are verywasteful, and tha

Explain what is file structure, Problem 1. List out the conditions that...

Problem 1. List out the conditions that result in Deadlock situations. Illustrate deadlock situation with a simple graphical notation Listing conditions for deadlock occu

What are the various layers of a file system, What are the various layers o...

What are the various layers of a file system? The file system is composed of many dissimilar levels. Each level in the design uses the feature of the lower levels to make new f

Why global variables are unacceptable, Why Global variables are unacceptabl...

Why Global variables are unacceptable Global variable, for instance, are unacceptable because they break the rules of self - containment. If all procedural components are runni

Algorithm for reconstructing a logical ring, Q. Present an algorithm for re...

Q. Present an algorithm for reconstructing a logical ring after a process in the ring fails? Answer: Typically distributed systems utilize a coordinator process that performs

Define where a program generation activity aims, Define where a Program gen...

Define where a Program generation activity aims  Program generation activity aims at Automatic generation of program

Which algorithm makes the most efficient use of memory, Question : (a) ...

Question : (a) The dynamic allocation problem is how to satisfy a request of size n from a list of free holes into memory. The best-fit, first-fit and worst-fit strategies are

Define the features to implement top down parsing, Define the features are ...

Define the features are needed to implement top down parsing                      Source string marker, Prediction making mechanism and Matching and Backtracking mechanism

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