Post on 21-Mar-2016
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MANAJEMEN PROYEKPERANGKAT LUNAK
Program Pendidikan VokasiUniversitas BrawijayaTahun 2011
Pertemuan 5
Perencanaan Proyek : PDM (Presedence Diagramming Method) CPM (Critical Path Method)
Critical Path Method Advantages: Identifies activities that control the project
length Determines shortest time for completion Identifies activities that are critical (i.e.
cannot be delayed) Shows available float for non-critical
activities Allows evaluation of “what-if” scenarios Allows monitoring & control of fast-track
projects With software can be resource loaded and
leveled
Critical Path Method Disadvantages Only as good as the effort put forth to
properly model the plan Can be difficult to properly update Can be easily misused May lead to a false sense of security Actual conditions may necessitate
significant modifications to model to accurately reflect reality
Precedence Diagramming Method (PDM) PDM network rules:
Activities are represented by boxes or nodes that are assigned properties of the activity they represent
Precedences are shown by arrows that have both direction and time properties
Precedences consist of two parts: A relationship and a lag value or constraint Finish – to – Start FS Finish – to – Finish FF Start – to – Start SS Start – to – Finish SF
Lag = x Days ( a negative lag is
called a lead)
PDM – Precedence Diagram PDM activities are comprised of:
Activity descriptions Nodes representing the activity Arrows representing relationship /
dependency Points indicating direction of relationship /
dependency
PDM Logic RelationshipsFinish to Start (FS) – Activity A must Finish before Activity B may Start.The lag is usually zero. FS is the most common type.
Start to Finish (SF) – Activity A must start before Activity B may Finish. Thelag is usually greater than either activity duration. FS is the least common type.
Activity A Activity B
Activity A Activity B
PDM Logic RelationshipsFinish to Finish (FF) – Activity A must Finish before Activity B may Finish.The lag value is usually greater than zero. FF is a less common type.
Start to Start (SS) – Activity A must Start before Activity B may Start.The lag value is usually greater than zero. SS is a less common type.
Activity A Activity B
Activity A Activity B
PDM Time Calculations Once the Network is constructed and duration of
each activity is estimated, we can determined the following four time values: Earliest Start (ES) – The earliest possible time an
activity can begin Earliest Finish (EF) – The earliest possible time an
activity can finish Latest Start (LS) – The latest possible time an activity
can start without delaying project completion Latest Finish (LF) – The latest possible time an activity
can start without delaying project completion
PDM Time Calculations ES and EF are determined by making a
Forward Pass (left-to-right) through the Network. ES of an activity is equal to the latest of early finish times of its predecessors. EF is the total of the activity ES plus its duration.
LS and LF are determined by making a Backward Pass (right-to-left) through the Network. LF of an activity is equal to the smallest of the LS times of the activities exiting from the activity in question. LS of an activity is equal to its LF minus its duration.
PDM Activity Notation and Assumptions
Each activity box consists of six cells
For the following example assume all activities: Begin on the morning of the scheduled start
date End the evening of the scheduled finish date Using a 7-day workdays per week calendar
4 E 611 2 13
ES EFActivity
DurationLS LF
0 Lag
Forward Pass Example
6 D 94
8 E 81
4 F 107
12 G 187
2
0
0
(F to G) 10 + 0 + 1 = 11(E to G) 8 + 0 + 1 = 9(D to G) 9 + 2 + 1 = 12
Largest ES
Early Start Calculations
Early Finish Calculation12 + 7 – 1 = 18
Backward Pass Example
18 H 2425 7 31
18 I 2124 4 27
18 J 1834 1 34
14 K 1719 4 22
2
0
0
(H to K) 25 - 2 - 1 = 22(I to K) 24 - 0 - 1 = 23(J to K) 34 - 0 - 1 = 33
Late Finish Calculations
Late Start Calculation22 - 4 + 1 = 19
CPM Example Exercise
A6d
B11d
C20d
H20d
J20d
D13d
E9d
F20d
G6d
I13d
CPM Example ExerciseForward Pass Results
A6d
B11d
C20d
H20d
J20d
D13d
E9d
F20d
G6d
I13d
1d 6d 7d 17d 18d 37d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
34d 39d 40d 52d
CPM Example Exercise
Backward Pass Results
A6d
B11d
C20d
H20d
J20d
D13d
E9d
F20d
G6d
I13d
1d 6d 7d 17d 18d 37d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
34d 39d 40d 52d
4d 9d 10d 20d 43d 62d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
44d 49d 50d 62d
CPM Example Exercise
Backward Pass Results
A6d
B11d
C20d
H20d
J20d
D13d
E9d
F20d
G6d
I13d
1d 6d 7d 17d 18d 37d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
34d 39d 40d 52d
4d 9d 10d 20d 43d 62d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
44d 49d 50d 62d
CPM – Float (or Slack) and Critical Path
Additional Network calculations provides other important information allowing analysis and control: Total Float (TF) – The amount of time an
activity can be delayed without delaying the overall project completion, which is equal to Late Finish minus Early Finish.
Free Float (FF) – The amount of time an activity can be delayed without delaying the start of another activity. Can be determine by subtracting the smallest Total Float going into an activity from each predecessor into that activity.
Critical Path – The path through the Network that has the longest total duration, thus it defines the shortest period of time in which the project may be completed.
Float Calculation Example
CPM Example Exercise
Continue with Exercise
A6d
B11d
C20d
H20d
J20d
D13d
E9d
F20d
G6d
I13d
1d 6d 7d 17d 18d 37d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
34d 39d 40d 52d
4d 9d 10d 20d 43d 62d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
44d 49d 50d 62d
CPM Example ExerciseFloat Results
A6d
B11d
C20d
H20d
J20d
D13d
E9d
F20d
G6d
I13d
1d 6d 7d 17d 18d 37d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
34d 39d 40d 52d
4d 9d 10d 20d 43d 62d 63d 82d
1d 20d 21d 33d 34d 42d 43d 62d
44d 49d 50d 62d
3d 3d 25d 0d
0d 0d 0d 0d
10d 10d
CPM Example ExerciseCritical Path Traced
A1d 6d 6d4d 3d 9d
B7d 11d 17d10d 3d 20d
C18d 20d 37d43d 25d 62d
H63d 20d 82d63d 0d 82d
J1d 20d 20d1d 0d 20d
D21d 13d 33d21d 0d 33d
E34d 9d 42d34d 0d 42d
F43d 20d 62d43d 0d 62d
G34d 6d 39d44d 10d 49d
I40d 13d 52d50d 10d 62d
SEKIAN
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