Scheduling Overview

Scheduling a project or program aligns all the activities of each project on a common timeline based on the constraints, relationships, and the date types to which each activity must adhere. When the scheduler is run, the application applies the Critical Path Method algorithm to assign activity dates, calculate total float, and determine the project critical path.

Critical Path Method Overview

When you schedule a project or program, the Critical Path Method conducts a forward pass that calculates the earliest start and finish dates for each activity, based on the start or finish dates of predecessor activities as well as the duration of the activity itself. It then conducts a backward pass to calculate the latest start and finish dates for each activity, based on the start or finish dates of successor activities as well as the duration of the activity itself. From these dates, the total float is calculated for each activity to determine how much scheduling flexibility each activity has. Activities that have zero float must start on time to prevent the schedule from slipping. These are the activities that define the critical path. Identifying the critical path helps the project management team know where to focus their efforts by knowing which activities are critical to overall project success.

Multiple Float Paths Overview

You can calculate multiple float paths when running the scheduler to calculate the critical path and sub-critical paths on a project and on programs that include multiple projects. The critical path is the path of activities that will lead to the earliest possible completion of the projects. Calculating the sub-critical paths for a project allows you to keep track of activities that aren't currently on the critical path but could very easily become critical and affect your project's progress. Multiple float paths can be recalculated every time you schedule the project, meaning the values are kept up-to-date to reflect any evolutions in your project. Calculating multiple float paths does not impact the critical activities defined in the Scheduler Settings.

The Multiple Float Paths feature allows you to choose an ending activity for your calculations. This allows you to calculate multiple float paths up to important milestones in your projects instead of only the ending activity.

Primavera Cloud provides the option to calculate multiple float paths using activity free float or total float. The Free Float option calculates the float path based on driving activities, which also calculates the schedule's longest path. The Total Float option calculates your critical and sub-critical paths based on the criticality of the Relationship Total Float for your activities.

How are multiple float paths calculated using free float?

The free float calculation first identifies the activity that has an early finish equal to the latest calculated early finish for the project or the activity that you identify as the ending activity for multiple float paths when scheduling your project. From this activity, the application then traces a backwards path along relationships using the relationship free float values to identify the driving path of relationships. The activities on this path constitute the critical path.

The application removes the activities that have been assigned to a path, and runs the calculation again to calculate the sub-critical paths. This is repeated until the number of sub-critical paths that are set to be calculated is met or there are no more activities to add to paths.

Note: If you use different calendars for your schedule's activities, the activities might not end up being calculated as part of the critical path even if they belong to the longest path.

If the application runs into an instance where there are equal values on the relationships and a tie breaker is needed, then the application goes through the following list to determine which activity to use:

Activity Free Float
Early Finish (latest date)
Early Start (earliest date)
Activity ID

How are multiple float paths calculated using total float?

First, the application will start with the latest activity relationship that has the most critical Relationship Total Float, meaning the least amount of Total Float, and will perform a backwards pass to determine the predecessors with the most critical Relationship Total Float until an open end on the path is reached. After the open end is reached, the application will then conduct a forward pass through the successor activities to identify the most critical activities by evaluating the Total Float of the successors. The forward pass continues until it reaches an open end on the path. The activities on this path are designated the critical path.

If the application runs into an instance where there are multiple activities with the same Relationship Total Float, then the application chooses the activities that have an activity type that is not Level of Effort. If there is a tie among those activities, the application goes through the following list until one of these values can serve as the tie breaker to determine which activity to use:

Activity Total Float
Activity Free Float
Early Finish (latest date)
Activity ID

How do I view multiple float path results?

The multiple float path results can be viewed on the Activities table.

The Float Path column indicates which float path an activity belongs to. Float path numbers are in order of criticality, with 1 being the critical float path, 2 being the next most critical float path, and so on. All float paths greater than 1 are considered the sub-critical float paths.

The Float Path Order column indicates the placement of an activity in the float path. This is based on the activity dates and relationships and goes in chronological order. Float paths do not include activities that have already been completed.

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Scheduling Log

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