Large Scale Systems DesignDr Dario Landa-Silva
1University of NottinghamSchool of Computer Science
Large Scale Systems DesignG52LSS
Lecture 8 – Gantt Charts and CPM
•Gantt Charts•Constructing Gantt Charts•Staff Profile and Utilisation
Learning outcomes: interpret the information in Gantt charts;construct Gantt charts following Pert/CPM method; determine staffprofile and staff utilisation for a project following the Gantt chartand staff requirements.
Large Scale Systems DesignDr Dario Landa-Silva
2University of NottinghamSchool of Computer Science
A project schedule represents the sequencing of theproject activities and milestones in a clear and logicalmanner to facilitate project execution and control.
After the PERT/CPM analysis is completed, thefollowing phase is to construct the GANTT chart andthen to re-allocate resources and re-schedule ifnecessary.
A GANTT chart is a useful graphical tool to aid projectmanagement. In a Gantt chart tasks are represented ashorizontal bars.
Gantt Charts
Large Scale Systems DesignDr Dario Landa-Silva
3University of NottinghamSchool of Computer Science
Characteristics of Gantt Charts
• The bar in each row identifies the corresponding task
• The horizontal position of the bar identifies start and end timesof the task
• Bar length represents the duration of the task
• Offer simple and good visual communication
• Task durations can be compared easily
• Good for allocating resources and re-scheduling
• Precedence relationships is represented using arrows
• Critical activities are usually highlighted
• Slack times are represented using bars with doted lines
• Milestones can be represented by special shapes
• Minor changes in data can cause major changes in the chart
Large Scale Systems DesignDr Dario Landa-Silva
4University of NottinghamSchool of Computer Science
Early start GANTT chart – the bar of each activitybegins at the activity earliest start time (ES).
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
5University of NottinghamSchool of Computer Science
Late start GANTT chart – the bar of each activity endsat the activity latest finish time (LF).
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
6University of NottinghamSchool of Computer Science
The steps to construct an early Gantt chart using theinformation obtained from the PERT/CPM analysis areas follows:
1. Schedule the critical tasks in the correct position2. Place the time windows in which the non-critical
tasks can be scheduled (ES and LF)3. Schedule the non-critical tasks according to their
earliest starting (ES) times4. Indicate precedence relationships between tasks
Note: to construct a late Gantt chart use the lateststarting (LS) time to schedule non-critical tasks.
Constructing Gantt Charts
Large Scale Systems DesignDr Dario Landa-Silva
7University of NottinghamSchool of Computer Science
Example 8.1 Construct an early Gantt chart for thefollowing project.
0440303
Slack
141410111146
LF
111084603
LS
14106
11843
EF
11644300
ES
3427543
Duration
C,DGEFBEBDAC
BA
PrecedenceTask
D(7)0/0
3/6
4/4
11/11
6/10
14/14
B(4)
A(3)
F(4)
C(5)
G(3)
E(2)
Large Scale Systems DesignDr Dario Landa-Silva
8University of NottinghamSchool of Computer Science
Example 8.1 (cont.)
Step 1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
9University of NottinghamSchool of Computer Science
Example 8.1 (cont.)
Step 2
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
10University of NottinghamSchool of Computer Science
Example 8.1 (cont.)
Step 3
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
11University of NottinghamSchool of Computer Science
Example 8.1 (cont.)
Step 4
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
12University of NottinghamSchool of Computer Science
Example 8.2 Construct a late Gantt chart for thefollowing project.
0 / 3A(3)2 / 5
0 / 0Start0 / 0
27 / 27End
27 / 27
3 / 8B(5)5 / 10
10 / 14E(4)
12 / 16
14 / 17F(3)
16 / 19
0 / 10C(10)0 / 10
10 / 17D(7)
10 / 17
17 / 19G(2)
17 / 19
24 / 27I(3)
24 / 27
19 / 24H(5)
19 / 24
Large Scale Systems DesignDr Dario Landa-Silva
13University of NottinghamSchool of Computer Science
Example 8.2 (cont.)
Step 1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
A
B
C
D
E
F
G
H
I
Step 2 Step 3 Step 4
Large Scale Systems DesignDr Dario Landa-Silva
14University of NottinghamSchool of Computer Science
The staff profile, showing the overall staff needs duringthe project, can be obtained with the project schedule(Gantt chart) and the staff requirements of each task.
Staff utilisation gives an indication of how the averageefficiency in which the available staff hours are beingutilised during the project.
Resource smoothing if often used to re-allocate resourcesand re-schedule activities when staff (or other resources)is not available at the required level. The non-criticaltasks are re-scheduled within their time windowavoiding as much overlap as possible.
Staff Profile and Utilisation
Large Scale Systems DesignDr Dario Landa-Silva
15University of NottinghamSchool of Computer Science
The staff profile is a graph that gives the total requiredstaff at every time in the project.
The staff utilisation is calculated by dividing the area ofstaff requirements by the area inside the staff profileenvelope.
projecttheofdurationtheis
at timeexecutedbeingactivitiesofsettheisactivityoftsrequiremenstafftheis
activityofdurationtheisactivitiesofnumbertheiswhere
max
onUtilisatiStaff
i
i
1
1
L
lAis
itn
Ls
st
i
AiiLl
n
iii
l
Large Scale Systems DesignDr Dario Landa-Silva
16University of NottinghamSchool of Computer Science
Example 8.3 Obtain the staff profile and staff utilisationfor the following project.
5213142
RequiredStaff
3427543
Duration
GFEDCBA
Task7
6
5
4
3
2
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
A
B
C
D
E
F
G
Large Scale Systems DesignDr Dario Landa-Silva
17University of NottinghamSchool of Computer Science
Example 8.3 (cont.)
5213142
RequiredStaff
3427543
Duration
GFEDCBA
Task7
6
5
4
3
2
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
%7.85857.084
1582215166nutilisatioStaff
Large Scale Systems DesignDr Dario Landa-Silva
18University of NottinghamSchool of Computer Science
Exercise 8.1 Construct the early Gantt, staff profile andcalculate staff utilisation for the following project.
E(8)0/0
8/14
4/5
21/21
10/13
28/28
C(4)
A(8)
F(6)
D(7)
G(8)5/5 13/13
B(5)
I(7)
H(6)
563522833
Staff
15282216106FH0211321138E,FG
0
306106
Slack
28
1313215514LF
21
75
14106
LS
28
101315458
EF
21
458000
ES
7
687458
Duration
D,GI
CFB,CEAD
CBA
PrecedenceTask
Large Scale Systems DesignDr Dario Landa-Silva
19University of NottinghamSchool of Computer Science
Exercise 8.1 (cont.)The early Gantt chart
A
B
C
D
E
F
G
H
I
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Large Scale Systems DesignDr Dario Landa-Silva
20University of NottinghamSchool of Computer Science
Exercise 8.1 (cont.)The staff profile and utilisation
151413121110987654321
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
%65.575765.0nutilisatioStaff
Large Scale Systems DesignDr Dario Landa-Silva
21University of NottinghamSchool of Computer Science
Additional Reading
Chapter 5 of (Maylor, 2003)
Chapter 3 of (Kendall and Kendall, 2005)