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PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.
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Transcript of PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.
![Page 1: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/1.jpg)
PSOP: Using Search to Find Better Resource-Leveled
SchedulesMatt Ginsberg
![Page 2: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/2.jpg)
© 2005 On Time Systems, Inc.
![Page 3: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/3.jpg)
© 2005 On Time Systems, Inc.
Scheduling to an Academic
• Use small examples to: Understand why scheduling is hard Develop possible solutions
• Eventually, evaluate candidate approaches based on performance on real problems
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PSOP: Using Search to Find Better Resource-Leveled
SchedulesMatt Ginsberg
![Page 5: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/5.jpg)
PSOP: Using Search to Find Better Resource-Leveled
SchedulesMatt Ginsberg
Why Scheduling is Like Tetris
![Page 6: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/6.jpg)
© 2005 On Time Systems, Inc.
Scheduling and Tetris
• The idea is to squish a lot of stuff into a small space
• It helps to know what’s coming
• I am terrible at both
![Page 7: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/7.jpg)
© 2005 On Time Systems, Inc.
• Fact: Computer scientists tend to work on problems at which they are personally lousy.
• Consequence: Beware of people who say that they are working on “general intelligence.”
![Page 8: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/8.jpg)
© 2005 On Time Systems, Inc.
Summary
• The idea is to squish a lot of stuff into a small space
• It helps to know what’s coming
• I am terrible at both• … but Tetris is much more
forgiving than scheduling is
![Page 9: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/9.jpg)
© 2005 On Time Systems, Inc.
A Scheduling Problem
• The capacity of the red resource is one.
• The capacity of the blue resource is infinite.
• The capacity of the purple resource is two.
![Page 10: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/10.jpg)
© 2005 On Time Systems, Inc.
How Scheduling Algorithms Work
1. Select the highest-priority unscheduled task whose predecessors have all been scheduled.
2. Schedule it at its current early start.
3. Repeat.
![Page 11: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/11.jpg)
© 2005 On Time Systems, Inc.
How Scheduling Algorithms Work
1. Select the highest-priority unscheduled task whose predecessors have all been scheduled.
2. Schedule it at its current early start.
3. Repeat.
![Page 12: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/12.jpg)
© 2005 On Time Systems, Inc.
Order Matters
1. Select the highest-priority unscheduled task whose predecessors have all been scheduled.
2. Schedule it at its current early start.
3. Repeat.
![Page 13: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/13.jpg)
© 2005 On Time Systems, Inc.
Order Matters
• The purple resource has capacity two.
• The bottom task should not be scheduled last.
![Page 14: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/14.jpg)
© 2005 On Time Systems, Inc.
Order Matters
• The purple resource has capacity two.
• The bottom task should not be scheduled last.
![Page 15: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/15.jpg)
© 2005 On Time Systems, Inc.
Schedule the Longest Task First?
1
2
3
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© 2005 On Time Systems, Inc.
Schedule the Longest Task First?
1
2
3
![Page 17: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/17.jpg)
© 2005 On Time Systems, Inc.
Schedule the Least Float Task First
2
3
1
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© 2005 On Time Systems, Inc.
No Obvious Order Works
longest, least float
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© 2005 On Time Systems, Inc.
No Obvious Order Works
longest, least float
![Page 20: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/20.jpg)
© 2005 On Time Systems, Inc.
The Example in Primavera
• Use a silly order• Prioritize by hand
longest, least float
![Page 21: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/21.jpg)
© 2005 On Time Systems, Inc.
No Order Works
![Page 22: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/22.jpg)
© 2005 On Time Systems, Inc.
Least Float First
least float
![Page 23: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/23.jpg)
© 2005 On Time Systems, Inc.
Most Float First?
least float
![Page 24: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/24.jpg)
© 2005 On Time Systems, Inc.
The Order That Works
• Prioritize by hand?least float
![Page 25: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/25.jpg)
© 2005 On Time Systems, Inc.
Prioritization by Hand
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© 2005 On Time Systems, Inc.
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© 2005 On Time Systems, Inc.
Prioritization by Hand
• Unlikely to work in practice• What can you do?• Being good at Tetris will not save you
![Page 28: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/28.jpg)
© 2005 On Time Systems, Inc.
Outline
• If you want a good schedule, prioritization matters• Not obvious how to prioritize automatically• Prioritization by hand is impractical• Schedule packing• Squeaky wheel optimization
How it works Strengths, weaknesses Access
![Page 29: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/29.jpg)
© 2005 On Time Systems, Inc.
Schedule Packing
WARNING: Contents may have settled
during shipping
![Page 30: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/30.jpg)
© 2005 On Time Systems, Inc.
Schedule Packing
1. Slide tasks as far to right as possible
2. Reschedule using start time as priority
1 2
3
4
![Page 31: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/31.jpg)
© 2005 On Time Systems, Inc.
Outline
• If you want a good schedule, prioritization matters• Not obvious how to prioritize automatically• Prioritization by hand is impractical• Schedule packing• Squeaky wheel optimization
How it works Strengths, weaknesses Access
![Page 32: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/32.jpg)
© 2005 On Time Systems, Inc.
Squeaky Wheel Optimization
• Too many priority orders to figure out the best one
• Use search
![Page 33: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/33.jpg)
© 2005 On Time Systems, Inc.
think search
• Primavera• schedule packing
• squeaky wheel
P=NP?
![Page 34: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/34.jpg)
© 2005 On Time Systems, Inc.
Solving Problems Using Search
• The key is to control the search
![Page 35: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/35.jpg)
© 2005 On Time Systems, Inc.
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![Page 36: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/36.jpg)
© 2005 On Time Systems, Inc.
Solving Problems Using Search
• The key is to control the search• A machine can look at many candidate
schedules, but it still needs to focus on schedules that are likely to be good
• Squeaky wheel: Analyze the current schedule before generating the next one
![Page 37: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/37.jpg)
© 2005 On Time Systems, Inc.
Squeaky Wheel Optimization
• C-A-P loop Construct Analyze Prioritize
![Page 38: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/38.jpg)
© 2005 On Time Systems, Inc.
Squeaky Wheel Optimization
• C-A-P loop Construct a schedule from current priorities Analyze Prioritize
![Page 39: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/39.jpg)
© 2005 On Time Systems, Inc.
Squeaky Wheel Optimization
• C-A-P loop Construct a schedule from current priorities Analyze to evaluate performance by task Prioritize
![Page 40: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/40.jpg)
© 2005 On Time Systems, Inc.
Squeaky Wheel Optimization
• C-A-P loop Construct a schedule from current priorities Analyze to evaluate performance by task Prioritize so that poorly scheduled tasks
become more important• The squeaky wheel gets the grease!
![Page 41: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/41.jpg)
© 2005 On Time Systems, Inc.
Squeaky Wheel Where no Order Worked
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Squeaky Wheel Where no Order Worked
• Search improves your ability to find good solutions, even if you guess wrong initially
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Schedule Packing on This Problem
![Page 44: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/44.jpg)
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Squeaky Wheel
![Page 45: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/45.jpg)
© 2005 On Time Systems, Inc.
Enough Already with the Toy Problems!• Turnaround data from existing Primavera customer• 12,248 tasks, analyzed in 4.5 minutes
Primavera length
PSOP length
Primavera overload
PSOP overload
Primavera leveled
47 days 40 days 43 hours 11 hours
Leveled within total float
30 days 30 days 10,561 hours 2,653 hours
![Page 46: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/46.jpg)
© 2005 On Time Systems, Inc.
Pros and Cons
Schedule Packing• Simple• Fast (because no search)• Patented by Boeing
Squeaky Wheel• Not so simple• Potentially slower because of search• Better coverage• Patented by U Oregon• Available as an addon for Primavera 5.0
![Page 47: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/47.jpg)
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PSOP Demo
![Page 48: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/48.jpg)
© 2005 On Time Systems, Inc.
One Last Example
sand and prepare
mix and paint
-1
![Page 49: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/49.jpg)
© 2005 On Time Systems, Inc.
One Last Example
• No predecessor-based algorithms works!• Squeaky wheel need not follow “network” order• Schedule packing does
sand and prepare
mix and paint
-1
![Page 50: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/50.jpg)
© 2005 On Time Systems, Inc.
Pros and Cons
Schedule Packing• Simple• Fast (because no search)• Patented by Boeing• Add search?
Squeaky Wheel• Not so simple• Potentially slower because of search• Still• Patented by U Oregon• Available as an addon for Primavera 5.0
Better coverage
![Page 51: PSOP: Using Search to Find Better Resource-Leveled Schedules Matt Ginsberg.](https://reader038.fdocuments.in/reader038/viewer/2022110320/56649cb95503460f949811ea/html5/thumbnails/51.jpg)
© 2005 On Time Systems, Inc.
Questions?