Forward Pass

 

Key Points:

1. Forward Pass Overview:

   • The forward pass calculates the Early Start (ES) and Early Finish (EF) for each activity in a project network diagram.
   • ES: The earliest an activity can start.
   • EF: The earliest an activity can finish.
   • This process is essential for determining the project timeline and identifying the critical path.

2. Forward Pass Steps:

   • Start the first activity at Day 1.
   • Calculate EF using the formula:
     EF = ES + Duration - 1.
   • For subsequent activities:
     • ES is set to the EF + 1 of the preceding activity.
     • For activities dependent on multiple predecessors, ES is based on the largest EF among them (e.g., path convergence).

3. Example Forward Pass Calculation:

   • Activity A:
     • ES = 1, Duration = 3.
     • EF = 1 + 3 - 1 = 3.
   • Activity B (follows A):
     • ES = 3 + 1 = 4, Duration = 2.
     • EF = 4 + 2 - 1 = 5.
   • Activity C (follows B):
     • ES = 5 + 1 = 6, Duration = 4.
     • EF = 6 + 4 - 1 = 9.
   • Activity D (follows B):
     • ES = 5 + 1 = 6, Duration = 3.
     • EF = 6 + 3 - 1 = 8.
   • Activity E (follows both C and D):
     • ES = max(EF of C, EF of D) + 1 = 9 + 1 = 10.
     • EF = 10 + 2 - 1 = 11.

4. Key Formula Explanation:

   • The minus one adjustment in the formula accounts for starting on the first day and fully using that day for the activity.

5. Handling Converging Paths:

   • When multiple activities converge into one, the ES of the successor activity is determined by the largest EF of all converging activities.

6. Critical Path Confirmation:

   • The EF of the final activity in the forward pass confirms the total project duration.
   • The calculated forward pass should match the critical path for consistency.

7. Quick Review of the Example:

   • Activity A: ES = 1, EF = 3.
   • Activity B: ES = 4, EF = 5.
   • Activity C: ES = 6, EF = 9.
   • Activity D: ES = 6, EF = 8.
   • Activity E: ES = 10, EF = 11.
   • Critical Path: A → B → C → E.

8. Next Steps:

   • The backward pass, which calculates the Late Start (LS) and Late Finish (LF) for each activity, will be covered in the next video.

---

Summary:

The forward pass is a critical step in project management for calculating the Early Start (ES) and Early Finish (EF) of activities in a network diagram. Starting from the first activity, ES is set to Day 1, and EF is calculated using the formula EF = ES + Duration - 1. For subsequent activities, ES is based on the EF of preceding activities, or the largest EF in the case of path convergence. This process not only determines the timeline for project completion but also validates the critical path. The next step is the backward pass, which will calculate the Late Start (LS) and Late Finish (LF) to complete the scheduling analysis.