A systematic method of choosing/creating a priority list, L, that - - PowerPoint PPT Presentation

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Mar 25, 2024 114 likes •186 views

Chapter 3: Planning and Scheduling Critical Path Schedules Critical-Path Schedules A systematic method of choosing/creating a priority list, L, that yields optimal, or nearly optional, schedules. Chapter 3: Planning and Scheduling

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Chapter 3: Planning and Scheduling Critical Path Schedules

 Critical-Path Schedules  A systematic method of choosing/creating a priority list, L, that yields optimal, or nearly

ptional, schedules.

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Chapter 3: Planning and Scheduling Critical Path Schedules

 Critical-Path Scheduling Algorithm (to create priority list L)

1. Find a task that heads a critical (longest) path in the
rder-requirement digraph. If a tie, choose the lowest-

number task.

2. Place the task found in step 1 next on the list L (the first

time through the process this task will head the list).

3. Remove the task found in step 1 and the edges attached

to it from the current order-requirement digraph, obtaining a new (modified) order-requirement digraph.

4. If there are no vertices left in the new order-requirement

digraph, the procedure is complete; if there are vertices left, go to step 1.

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Chapter 3: Planning and Scheduling Critical Path Schedules

This procedure will terminate when all the tasks in the

riginal order-requirement digraph have been placed on

the list L.

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Chapter 3: Planning and Scheduling Critical Path Schedules

 Example of Critical-Path Scheduling Algorithm

 For this order-requirement digraph, there are two critical paths of length 64: T1, T2, T3 and T1, T4, T3. Place T1 on the list L.  With T1 “gone,” there is a new critical path of length 60: T5, T6, T4, T3. Place T5 next on the list L.

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Chapter 3: Planning and Scheduling Critical Path Schedules

 With T1 and T5 “gone,” the next longest path would be 56: T6, T4, T3. Place T6 next on the list L. (Continue the algorithm until list is complete.)  The new priority list would be: L = T1, T5, T6, T2, T4, T3, T8, T9, T7, T10.

A systematic method of choosing/creating a priority list, L, that - - PowerPoint PPT Presentation

Chapter 3: Planning and Scheduling Critical Path Schedules

 Critical-Path Schedules  A systematic method of choosing/creating a priority list, L, that yields optimal, or nearly

Chapter 3: Planning and Scheduling Critical Path Schedules

 Critical-Path Scheduling Algorithm (to create priority list L)

number task.

time through the process this task will head the list).

to it from the current order-requirement digraph, obtaining a new (modified) order-requirement digraph.

digraph, the procedure is complete; if there are vertices left, go to step 1.

Chapter 3: Planning and Scheduling Critical Path Schedules

This procedure will terminate when all the tasks in the

the list L.

Chapter 3: Planning and Scheduling Critical Path Schedules

 Example of Critical-Path Scheduling Algorithm

 For this order-requirement digraph, there are two critical paths of length 64: T1, T2, T3 and T1, T4, T3. Place T1 on the list L.  With T1 “gone,” there is a new critical path of length 60: T5, T6, T4, T3. Place T5 next on the list L.

Chapter 3: Planning and Scheduling Critical Path Schedules

 With T1 and T5 “gone,” the next longest path would be 56: T6, T4, T3. Place T6 next on the list L. (Continue the algorithm until list is complete.)  The new priority list would be: L = T1, T5, T6, T2, T4, T3, T8, T9, T7, T10.

Using the list-processing algorithm with the original

L, the following schedule is obtained:

Chapter 3: Planning and Scheduling Critical Path Schedules

So the optimal schedule produced has a time of 64.