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

Interrupt-driven i/o to manage a single serial port, Q. Why might a system ...

Q. Why might a system utilize interrupt-driven I/O to manage a single serial port however polling I/O to manage a front-end processor such as a terminal concentrator? A

Server thread, Extend task 1 so that the requests are issued by the clients...

Extend task 1 so that the requests are issued by the clients instead of the server. The server now do not use the "all_requests.dat" file. Instead every client thread reads from

What are the advantages and disadvantages of multithreading, What are the a...

What are the advantages and disadvantages of multithreading?  Advantages : Since by multithreading multiple executions are carried out in the same process environment t

Reference counting, The idea of reference counting is to maintain, for ever...

The idea of reference counting is to maintain, for every object, the total number of references to that object, i.e. the number of "incoming" pointers. Whenever the number of refer

Inventory differences, What makes a Just-in-Time inventory system differ fr...

What makes a Just-in-Time inventory system differ from a traditional inventory system?

Explain threads for executing concurrent application code, Explain Threads ...

Explain Threads for Executing Concurrent Application Code The thread has been introduced in many operating systems as an efficient mechanism for executing concurrent applicatio

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

How is the NTFS namespace planned, Q. How is the NTFS namespace planned? Ex...

Q. How is the NTFS namespace planned? Explain. Answer: The NTFS namespace is prearranged as a hierarchy of directories where every directory uses a B+ tree data structure to

Declare some applications of open source systems, Declare some Applications...

Declare some Applications of Open Source Systems • Finance • Educational • Data Storage and Management • ERP (Enterprise Resource Planning) •File Sharing & FTP

Compute how many disk input - output operations are required, Q. Consider ...

Q. Consider a file at present consisting of 100 blocks. Presume that the file control block (and the index block in the case of indexed allocation) is already in memory. Compute h

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