critical path analysis Flashcards
what is critical path analysis?
critical path analysis is a technique that identifies the activities required to complete a project, the time necessary to complete each activity and the relationships between the activities
what is an activity chart?
a table containing the activities of a project, their duration and their immediate predecessors
what are dummy activities on a network?
- a dummy activity is required if two activities share some, but not all, of their immediate predecessors
- a dummy activity is not real but imaginary, and so it takes no time (its duration is 0)
how does scheduling on a network diagram work?
scheduling on a network diagram is shown using a weighted edge. the number on the edge indicates the duration of the activity. the weight of dummy activities is always zero
how does forward scanning work on a network?
for a project to be completed in the shortest time possible, it is important to be aware of each activity’s earliest starting time (EST) after the start of the entire project. an EST of 8 means an activity cannot start until 8 hours (or whatever time unit is given) after the start of the project. the EST for each activity is found by a process called forward scanning
how does backward scanning work on a network?
some activities have some flexibility around the time they can start. the latest start time, or LST, for each activity is the latest time after the start of the project that the individual activity can start for the project to still be completed in the minimum time. LSTs for each activity are calculated using the reverse of the process used to calculate the ESTs. this process is called backward scanning
what is a float time on a network?
float time is the amount of time that a task in a project network can be delayed without causing a delay to subsequent tasks
how is float time calculated?
float time is calculated by subtracting the earliest start time from the latest start time
float time = LST - EST
what is the critical path of a network?
the critical path is the sequence of the critical activities. critical activities are ones that cannot be delayed without affecting the overall completion time of the project
what is the minimum time of a network?
the minimum overall completion time of the project is the EST value at the finish
what is the maximum flow of a network?
if pipes of different capacities are connected one after the other, the maximum flow (or flow capacity) through the pipes is equal to the maximum capacity of the individual smallest pipe
how does a cut work in a network?
- a cut is an imaginary line across a directed graph that completely separates the source (start of the flow) from the sink (destination of the flow)
- cut capacity is the sum of all the capacities of the edges that the cut passes through, taking into account the direction of flow. the capacity of an edge is only counted if it flows from the source side to the sink side of the cut
- a cut is like a snapshot across the system of the flow at that time
what is the maximum flow-minimum cut theorem?
the flow through a network cannot exceed the value of any cut in the network and the maximum flow equals the value of the minimum cut
