cpm critical path method
Post on 16-Apr-2017
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CPM – Critical Path Method
CPM – Critical Path Method
Software Project Management 2Maria Petridou
• It is determined by adding the times for the activities in each sequence.
• CPM determines the total calendar time required for the project.• If activities outside the critical path speed up or slow down (within
limits), the total project time does not change.• The amount of time that a non-critical activity can be delayed
without delaying the project is called slack-time.
CPM – Critical Path Method
Software Project Management 3Maria Petridou
ET – Earliest node time for given activity duration and precedence relationships
LT – Latest node time assuming no delays
ES – Activity earliest start time LS – Activity latest start time EF – Activity earliest finishing time LF – Activity latest finishing time Slack Time – Maximum activity delay time
Dummy Activities
Software Project Management 4Maria Petridou
• Sometimes it is necessary to insert dummy activities (duration zero) in order to maintain the clarity of the diagram and the precedence relationships between activities.
• In activity-on-arrow PERT diagrams, each activity must be uniquely identifiable by its start and end nodes.
• However, sometimes multiple tasks have the same predecessors and successors.
Dummy Activities
Software Project Management 5Maria Petridou
Case One• A task should be uniquely identifiable from its start node and finish
node This means that two or more tasks cannot share the same start
and finish nodes
1 2 3 4A D
C Tasks B and C have the same start and finish
nodes
Task D has immediate
predecessors of B and C
B
Network Planning Techniques• Program Evaluation & Review Technique (PERT):– Developed to manage the Polaris missile project– Many tasks pushed the boundaries of science &
engineering (tasks’ duration = probabilistic)
• Critical Path Method (CPM):– Developed to coordinate maintenance projects in the
chemical industry– A complex undertaking, but individual tasks are routine
(tasks’ duration = deterministic)
PERT and CPM
• Graphically display the precedence relationships & sequence of activities
• Estimate the project’s duration• Identify critical activities that cannot be
delayed without delaying the project• Estimate the amount of slack associated with
non-critical activities
8
Project Activitiesin Constructing a House
9
PERT Network forConstructing a House
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