Gantt chart and PERT chart

Source: Internet
Author: User

A Gantt chart is also called a Gantt chart.
Progress is a list of activities planned in chronological order, which is called the Gantt chart. It has the following key components:
1. A calendar table is arranged across the top of the graph.
2. The leftmost column contains the ID of each task ).
3. The second column on the left is the name of the task to be executed.
4. In the chart, the task bar indicates the start time and end time of each task plan.
5. At the bottom left of the table, the project name, the author of the Progress table, and the original date on which the progress was developed.

The Gantt chart is a useful tool for displaying the progress of each task in the project. This type of chart is particularly useful for coordinating multiple activities.

PERT Graph

PERT (Plan Review Technology)-calculates the total project time using the project network diagram and estimated time required for each activity (obtained through weighted average. The main difference between pert and CPM is that it uses expectations rather than the estimated time required for the most likely activity (used in CPM ). Currently, the PERT method is rarely used. However, estimation methods similar to Petr are often used in the CPM method.

CPM: calculates the earliest or latest start and end times of each activity based on the network diagram and the time required for each activity (estimated. The key of the CPM method is to calculate the total time difference, which determines which activity has the minimum time elasticity. CPM algorithms are also applied to other types of mathematical analysis.

In the PERT/CPM diagram, the following elements are generally included: task, milestone, start and end event, dependency between tasks

A pert graph shows the graphical interpretation of a project. This graph is installed on the network and consists of nodes marked by numbers. nodes are connected by line segments with labeled direction arrows, displays events or turning points in the project and tasks in the project. A line segment with a direction arrow indicates the sequence of tasks. For example, in the PERT graph, tasks between nodes 1, 2, 4, 8, and 10 must be completed in order, which is called the dependency of series tasks.

Commonly used graphical descriptions of schedules include the Gantt Chart (Gantt) and the plan review technical chart (PERT ).
(1) Gantt (Gantt) diagram: horizontal line segments are used to represent the work phase of a task. The start and end points of a line segment correspond to the start time and completion time of the task respectively; the length of a line segment indicates the time required to complete the task.
Advantage: it can clearly describe the start time, end time, and parallelism between tasks.
Disadvantages: the dependencies between tasks cannot be clearly reflected, the key of the entire project cannot be determined, and potential components in the plan cannot be reflected.
(2) pert graph: the PERT graph is a directed graph. The directed arc graph shows the task, which can mark the time required to complete the task; the node in the figure indicates the end of the task at the inbound node and starts the task at the outbound node. Here, the node is called an event. Only when all the tasks that flow into the node end, the event indicated by the node appears, and the task of the outbound node can start. The event itself does not consume time and resources. It only indicates a certain time point. Each event has an event number and the earliest and latest time when the event occurs. Each task also has a relaxation time, indicating how much maneuver is needed to complete the task without affecting the entire construction period. Tasks with a relaxation time of 0 constitute the key path for completing the entire project.
The pert graph not only shows the start time, end time, and time required to complete the task, but also shows the relationship between tasks, that is, which tasks can start other tasks after they are completed, and the key path to complete the project on schedule.

The relaxation time indicates that the start time of a task can be postponed or the completion time needed can be extended. However, the PERT graph does not reflect the parallel relationship between tasks.


Gantt chart and PERT chart

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