Identifying parallelism, Operating System

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.

Posted Date: 6/29/2012 2:06:10 AM | Location : United States







Related Discussions:- Identifying parallelism, Assignment Help, Ask Question on Identifying parallelism, Get Answer, Expert's Help, Identifying parallelism Discussions

Write discussion on Identifying parallelism
Your posts are moderated
Related Questions
General Graph Directory A serious trouble with using an acyclic graph structure is making sure that there are no cycles. When links are further added to an existing tree struc

Parent and Child process communicate in unix A child and parent can interact through any of the normal  inter-process communication schemes (pipes, message queues, sockets, s

protection in operating system

Refer a program with a linked origin of 5000. Suppose the memory area allocated to it have the start address of 70000. Determine the value to be loaded in relocation register?

Q. Describe the three main architectural layers of Windows XP? Answer: (1) The HAL (Hardware Abstraction Layer) creates operating system portability by hiding hardware differ

linked allocation using i node

Explain about file allocation methods? The main problem in direct-access nature is how to assign space to these files so that disk space if utilized effectively and files can b

Take the binary number and divide it into groups of 4 bits starting from the right hand side , if no group of 4 exists fill out leading 0's, then convert each group of 4 to a hex n

discuss unsafe state in operating system

The different paging techniques are 1. Multilevel paging or hierarchical paging method: In definite cases the page table may consist up to 1 million entries. This would be