spm, cpm, it

CRITICAL CRITICAL PATH PATH

METHOD(CPMETHOD(CPM) M)

Presented by : Manohar Presented by : Manohar Prasad,Prasad,

Specialization: IB+ITSpecialization: IB+IT

Roll No.-1999/01030003Roll No.-1999/01030003

CRITICAL PATH CRITICAL PATH METHODMETHOD

• All project management techniques compute All project management techniques compute what is called a critical path. Since a project what is called a critical path. Since a project consists of an ordered set of independent consists of an ordered set of independent activities, it can be represented as network.activities, it can be represented as network.

• A path through the network is any set of A path through the network is any set of successive activities, which goes from the successive activities, which goes from the beginning to the end of the project beginning to the end of the project associated with each activity in the network associated with each activity in the network is a single number that best estimates the is a single number that best estimates the time that activity will consume.time that activity will consume.

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• A critical path, then, is one whose sum of A critical path, then, is one whose sum of activity time is longer than that for any other activity time is longer than that for any other through the network. This path is important through the network. This path is important because, if everything goes according to because, if everything goes according to schedule, its length gives the shortest possible schedule, its length gives the shortest possible completion time of the overall project.completion time of the overall project.

• In addition, a slack time can be associated In addition, a slack time can be associated with each activity in the project. This is the with each activity in the project. This is the difference between the latest possible difference between the latest possible completion time of each activity that will not completion time of each activity that will not delay the completion of the overall project and delay the completion of the overall project and the earliest possible completion time based on the earliest possible completion time based on all predecessor activities.all predecessor activities.


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• Activities on a critical path have zero Activities on a critical path have zero slack time and conversely, activities slack time and conversely, activities with zero slack time are on critical path.with zero slack time are on critical path.

Steps to Determine CPMSteps to Determine CPM

• Build the Network.Build the Network.• Put in all Precedence Relationships.Put in all Precedence Relationships.• Calculate EST, LST, EFT, LFT.Calculate EST, LST, EFT, LFT.• Work Forward and Backward.Work Forward and Backward.• Determine Slack Time.Determine Slack Time.• Determine Critical Path.Determine Critical Path.


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Example:Example:Activities Predecessors DurationA --- 5

B --- 4

C A 3

D A 4

E A 6

F B, C 4

G D 5

H D, E 6

I F 6

J G, H 4


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Building the CPM Building the CPM Network :Network :

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Start

Finish

A 5

D 4

E 6

C 3

G 5

H 6

J 4

I 6

F 4

B 4

Calculate Calculate EST/LST :EST/LST :

• Go through the chains to find the longest Go through the chains to find the longest path-path-

• ADGJ = 18ADGJ = 18• AEHJ = 21AEHJ = 21• ADHJ = 19ADHJ = 19• ACFI = 18ACFI = 18• BFI = 18BFI = 18• Here AEHJ = 21 days is the longest Here AEHJ = 21 days is the longest

chain.chain.


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Calculate Calculate LST/LFT :LST/LFT :

• Work backward from 21 days on Work backward from 21 days on each activity .each activity .


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Building the CPM Building the CPM Network :Network :


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Start

Finish

A 5

D 4

E 6

C 3

G 5

H 6

J 4

I 6

F 4

B 4

0 5

0 55

5

11

11

11

11

17

17

17

17

21

21

21

15

12

18

15

12

8

11

11

4

7

0

11

8

85

11

7

959 1

4

17

12


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Name Duration

EST

EFT

LST LFT

Calculation of Slack :

Slack = LST – EST Or LFT - EFT

ResulResultt

Activity LST - EST LFT – EFTA 0 0

B 7 7

C 3 3

D 2 2

E 0 0

F 3 3

G 3 3

H 0 0

I 3 3

J 0 0

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m 12


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