Decision Maths: 8. Critical Path Analysis Flashcards
What is the Late Event Time
The late event time is the latest time that the event can be left without extending the time needed for the project.
What is the Early Event Time
The early event time is the earliest time of arrival at the event allowing for the completion of all preceding activities.
How are the Early Event times calculated
The early event times are calculated starting from 0, and working towards the sink node. This is called a forward pass or forward scan.
How are the Late Event times calculated
The late event times are calculated starting from the sink node and working backwards towards the source node. This is called a backwards pass or backward scan.
What is a Forward Pass and How is it done?
A forward pass is used to calculate the early event time. The largest value is always taken when calculating early times, because it is not possible to get to the event until all preceding activities have been completed.
What is a Backward Pass and How is it done?
A backward pass is used to calculate the late event times. The smallest value is always taken when calculating late times, because if you left the event later than the project would be delayed.
What are Critical Events
Critical events are ones where the early time is equal to the late time.
What are Critical Activities
Critical activities are those between critical events when ‘Event Time A + Activity Time = Event Time B’.
What is the Float of an Activity
The float of an activity is the amount of time that it’s start may be delayed without affecting the duration of the project.
How do you work out the float of an activity
Total float = latest finish time - duration - earliest start time.
The total float of any critical activity is zero.
What can Grant Charts be used for
Gantt charts can be used to determine which activities must be happening at any given time and those that may be happening at a given time.
What is a Eulerian Trail/Eulerian Cycle
A Eulerian trail or Eulerian cycle cover every edge of the graph exactly once and finishes at rage start vertex.
What makes a Graph Eulerian
A graph is Eulerian if it is possible to find a Eulerian trail on the graph.
A graph will be Eulerian is all the vertices are even
What makes a graph Semi-Eulerian
A graph is called semi-Eulerian if it is possible to cover every edge exactly once by starting at one vertex and finishing at another.
A graph will be sent-Eulerian if 2 of the vertices are odd.
What is a Traversable Graph
A graph that can be drawn without taking the one off the paper and without repeating any edges is called traversable.
