Scheduling resources

Having produced the resource requirements list, the next stage is to map this onto the activity plan to assess the distribution of resources required over the duration of the project. This is best done by representing the activity plan as a bar chart and using this to produce a resource histogram for each resource.

Figure 8.3 illustrates Amanda's activity plan as a bar chart and a resource histogram for analyst-designers. Each activity has been scheduled to start at its earliest start date - a sensible initial strategy, since we would, other things being

Table 8.1 Part of Amanda \s resource requirements list

Stage

Activity

Resource

Days

Quantity Notes

ALL

Project manager

104 F/T

1

All

Workstation

34

Check software availability

IoE/P/1

Senior analyst

34 F/T

2

All

Workstation

-

3

1 per person would be ideal

IoE/P/2

Analyst-designer

20 F/T

IoE/P/3

Analyst-designer

15 F/T

IoE/P/4

Analyst-designer

25 F/T

IoE/P/5

Analyst-designer

15 F/T

Could use analyst-programmer

3

All

Workstation

2 F/T

IoE/P/6

Senior analyst*

2 F/T

4

All

Workstation

-

3

As stage 2

IoE/P/7

Analyst-designer

7 F/T

IoE/P/8

Analyst-designer

6 F/T

IoE/P/9

Analyst-designer

4 F/T

IoE/P/10

Analyst-designer

4 F/T

5

All

Workstation

4

1 per programmer

All

Office space

-

If contract programmers used

IoE/P/11

Programmer

30 F/T

IoE/P/12

Programmer

28 F/T

IoE/P/13

Programmer

15 F/T

IoE/P/14

Programmer

25 F/T

6

All

Full machine access —

Approx. 16 hours for full system test

IoE/P/15

Analyst-designer

6 F/T

In reality, this would normally he done by a review involving all the analysts working on stage 2.

equal, wish to save any float to allow for contingencies. Earliest start date scheduling, as is the case with Amanda's project, frequently creates resource histograms that start with a peak and then tail off.

Changing the level of resources on a project over time, particularly personnel, generally adds to the cost of a project. Recruiting staff has costs and even where staff are transferred internally, time will be needed for familiarization with the new project environment.

The resource histogram in Figure 8.3 poses particular problems in that it calls for two analyst-designers to be idle for eleven days, one for six days and one for two days between the specification and design stage. It is unlikely that IOE would have another project requiring their skills for exactly those periods of time and this raises the question as to whether this idle time should be charged to Amanda's

White rectangles indicate when an activity is scheduled and shaded rectangles the total float.

Week number

Specify overall system

| Speci

y module A

| Specify module! B

Specify module C

Specify modulelD

Check specifications^

Design module A [

Design module B

Design module C

Design module D

Figure 8.3 Part of Amanda \s bar chart and resource histogram for analyst-

designers.

project. The ideal resource histogram will be smooth with, perhaps an initial buildup and a staged run-down.

An additional problem with an uneven resource histogram is that it is more likely to call for levels of resource beyond those available. Figure 8.4 illustrates how, by adjusting the start date of some activities and splitting others, a resource histogram can, subject to constraints such as precedence requirements, be smoothed to contain resource demand at available levels. The different letters represent staff working on a series of module testing tasks, that is, one person working on task A, two on tasks B and C etc.

In Figure 8.4, the original histogram was created by scheduling the activities at their earliest start dates. The resource histogram shows the typical peaked shape

A

A

B

B

B

B

B

B

Tester

C

C

C

C

C

C

F

F

H

H

H

availability

C

C

C

C

C

C

F

F

H

H

H

D

D

D

D

D

D

D

D

D

D

D

D

D

H

E

E

E

E

E

E

G

G

G

G

G

G

G

H

H

E

E

E

E

E

E

G

G

G

G

G

G

G

I

H

K K K

E

E

E

E

E

E

G

G

G

G

G

G

G

J

J

J J J J J

The majority of project planning software applications will produce resource histograms based on earliest activity start dates.

Tester availability QCCCCCCCCCBBBCDDDD

DDDDDDBBB E EGGGGGGG E EGGGGGGG E EGGGGGGG

Figure 8.4 A resource histogram showing demand for staff before and after smoothing.

caused by earliest start date scheduling and calls for a total of nine staff where only five are available for the project.

By delaying the start of some of the activities, it has been possible to smooth the histogram and reduce the maximum level of demand for the resource. Notice that some activities, such as C and D, have been split. Where non-critical activities can be split they can provide a useful way of filling troughs in the demand for a resource, but in software projects it is difficult to split tasks without increasing the time they take.

Some of the activities call for more than one unit of the resource at a time -activity F, for example, requires two programmers, each working for two weeks. It might be possible to reschedule this activity to use one programmer over four weeks although that has not been considered in this case.

Some project planning applications will carry out resource smoothing automatically, although they are unlikely to take into account all the factors that could be used by a project manager

Amanda has already decided to use only three analyst-designers on the project in Exercise 8.1 order to reduce costs. Her current resource histogram, however, calls for four during both stage 2 and stage 4. Suggest what she might do to smooth the histogram and reduce the number of analyst-designers required to three.

In practice, resources have to be allocated to a project on an activity-by-activity basis and finding the 'best' allocation can be time consuming and difficult. As soon as a member of the project team is allocated to an activity that activity acquires a scheduled start and finish date and the team member becomes unavailable for other activities for that period. Thus, allocating a resource to one activity limits the flexibility for resource allocation and scheduling of other activities.

It is therefore helpful to prioritize activities so that resources can be allocated to competing activities in some rational order. The priority must always be to allocate resources to critical path activities and then to those activities that are most likely to affect others. In that way, lower priority activities are made to fit around the more critical, already scheduled activities. Of the various ways of prioritizing activities, two are described below.

Total float priority Activities are ordered according to their total float, those with the smallest total float having the highest priority. In the simplest application of this method, activities are allocated resources in ascending order of total float. However, as scheduling proceeds, activities will be delayed (if resources are not available at their earliest start dates) and total floats will be reduced. It is therefore desirable to recalculate floats (and hence reorder the list) each time an activity is delayed.

Ordered list priority With this method, activities that can proceed at the same time are ordered according to a set of simple criteria. An example of this is Burman's priority list, which takes into account activity duration as well as total float:

1. shortest critical activity;

2. critical activities;

3. shortest non-critical activity;

4. non-critical activity with least float;

5. non-critical activities.

Unfortunately, resource smoothing, or even containment of resource demand to available levels, is not always possible within planned time-scales - deferring activities to smooth out resource peaks often puts back project completion. Where that is the case, we need to consider ways of increasing the available resource levels or altering working methods.

Exercise 8.2 Amanda finds that, with only three analyst-designers the specification of module

D (see Figure 8.3) will have to be deferred until after the specification of module B and this will add five days to the overall project duration (making 109 in total). She had hoped to have the project completed within 100 days and this is a further disappointment. She therefore decides to have another look at her activity plan.

P. J. Burman, Precedence Networks for Planning and Control, McGraw-Hill, 1972.

You will remember that early on she decided that she should check all of the specifications together (activity IoE/P/6) before allowing design to start. It is now apparent that this is causing a significant bottleneck and delaying module D will only exacerbate the problem. She therefore decides on a compromise - she will check the specifications for modules A, B and D together but will then go ahead with their design without waiting for the module C specification. This will be checked against the others when it is complete.

She redraws her precedence network to reflect this, inserting the new activity of checking the module C specification against the others (activity IoE/P/6a). This is shown in Figure 8.5. Draw a new resource histogram to reflect this change.

loE/P/2 20 days

Specify module A

Specify module B

5b Design b^

59~| module Bp65

IoE/P/61 2 days loE/P/15j 6 days

93 System I 99 93 ntegratior 99

Check specs loE/P/5

loE/P/9

Check spec bU Design _b4 74 module C 78

Activity label

Duration ra-liesl start

Latest

Activity span

Activity d«scnpbon

loE/P/1 I 34 d

ays

0 0

Specify overall system

34 34

34 days | Odays

34

Specify

49

39

module D

54

loE/P/10 4 days

56

Design

60

64

module D

68

12 days I 8 days

loE/P/111 30 days

63

Code/test

93

63

module A

93 i

30 days 0 days | ^

loE/P/12) 28 days

62

Code/test module B

90

65

93

31 days 3 days

loE/P/4 25 c

ays

34

Specify module C

59

48

73

39 days I 14 days

60

Code/test

85

68

module D

93

loE/P/71

7

days

56

Des

qn

63

56

modu

le A

63

7 days

Odays

64

Code/test

79

78

module C

Figure 8.5 Amanda \s revised precedence network.

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook


Responses

  • nasih
    What is ioe precedence network?
    4 years ago

Post a comment