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Course Missive
CS2750
Spring
In Deo Speramus
Brown
Apr 18, 2023 © 2014 Maurice Herlihy 2
Our Mission
• Learn how to– Come up-to-speed on a research area– Read a research paper– Map out an area from a paper– Present results to an audience
Apr 18, 2023 © 2014 Maurice Herlihy 3
The Two Generals
Red army winsIf both sides
attack together
Apr 18, 2023 © 2014 Maurice Herlihy 4
Communications
Red armies send messengers across valley
Apr 18, 2023 © 2014 Maurice Herlihy 5
Communications
Messengers don’t always make it
Apr 18, 2023 © 2014 Maurice Herlihy 6
Your Mission
Design a protocol to ensure that Red armies attack
simultaneously
Apr 18, 2023 © 2014 Maurice Herlihy 7
Theorem
There is no non-trivial protocol that ensures that the Red
armies attack simultaneously
Apr 18, 2023 © 2014 Maurice Herlihy 8
Proof Strategy
• Assume a protocol exists
• Reason about its properties
• Derive a contradiction
Apr 18, 2023 © 2014 Maurice Herlihy 9
Proof
1. Consider the protocol that sends fewest messages
Apr 18, 2023 © 2014 Maurice Herlihy 10
Proof
1. Consider the protocol that sends fewest messages
2. It still works if last message lost
Apr 18, 2023 © 2014 Maurice Herlihy 11
Proof
1. Consider the protocol that sends fewest messages
2. It still works if last message lost
3. So just don’t send it– Messengers’ union pleased
Apr 18, 2023 © 2014 Maurice Herlihy 12
Proof
1. Consider the protocol that sends fewest messages
2. It still works if last message lost
3. So just don’t send it– Messengers’ union happy
4. But now we have a shorter protocol!
Apr 18, 2023 © 2014 Maurice Herlihy 13
Proof
1. Consider the protocol that sends fewest messages
2. It still works if last message lost
3. So just don’t send it– Messengers’ union happy
4. But now we have a shorter protocol!
5. Contradicting #1
Apr 18, 2023 © 2014 Maurice Herlihy 14
Advisor
You May Find Yourself …
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You
Apr 18, 2023 © 2014 Maurice Herlihy 15
Advisor
You May Find Yourself …
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You
I’m so Pwned…
Apr 18, 2023 © 2014 Maurice Herlihy 16
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
Yes, Ma’am, right away!Yes, Ma’am, right away!
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 17
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
Yes, Ma’am, right away!Yes, Ma’am, right away!
Advantage:•Buys time to find another advisor.•No one really expects software to work anyway
Advantage:•Buys time to find another advisor.•No one really expects software to work anyway
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 18
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
Yes, Ma’am, right away!Yes, Ma’am, right away!
Advantage:•Buys time to find another job•No one really expects software to work anyway
Advantage:•Buys time to find another job•No one really expects software to work anyway
Disadvantage:•You’re doomed
Disadvantage:•You’re doomed
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 19
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
I can’t find a fault-tolerant algorithm, I guess I’m just a
pathetic loser.
I can’t find a fault-tolerant algorithm, I guess I’m just a
pathetic loser.
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 20
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
I can’t find a fault-tolerant algorithm, I guess I’m just a
pathetic loser.
I can’t find a fault-tolerant algorithm, I guess I’m just a
pathetic loser.
Advantage:•No need to take CS275
Advantage:•No need to take CS275
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 21
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
I can’t find a fault-tolerant algorithm, I guess I’m just a
pathetic loser.
I can’t find a fault-tolerant algorithm, I guess I’m just a
pathetic loser.
Advantage:•No need to take CS275
Advantage:•No need to take CS275
Disadvantage:•Advisor fires you, uses grant money to hire undergraduates
Disadvantage:•Advisor fires you, uses grant money to hire undergraduates
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 22
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
Using skills honed in CS275, I discovered prior work that suggests we had better rethink the problem spec.
Using skills honed in CS275, I discovered prior work that suggests we had better rethink the problem spec.
YouAdvisor
Apr 18, 2023 © 2014 Maurice Herlihy 23
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
I want a real-time ROTFL- compliant Two Generals
protocol using UDP datagrams running on our enterprise-level
fiber tachyion network ...
You might say
Using skills honed in CS275, I discovered prior work that suggests we had better rethink the problem spec.
Using skills honed in CS275, I discovered prior work that suggests we had better rethink the problem spec.
YouAdvisor
Tenure-track!
Apr 18, 2023 © 2014 Maurice Herlihy 24
Our Mission
• Learn how to– Come up-to-speed on a research area– Read a research paper– Map out an area from a paper– Present results to an audience
Apr 18, 2023 © 2014 Maurice Herlihy 25
Reading a Research Paper
• Many research papers are badly written– Conference deadlines– Conference page limits– Brilliant but inarticulate authors
Apr 18, 2023 © 2014 Maurice Herlihy 26
Leslie Lamport Review
Apr 18, 2023 © 2014 Maurice Herlihy 27
Leslie Lamport ReviewBadly-written, misunderstood paper
that few had read.
Apr 18, 2023 © 2014 Maurice Herlihy 28
Continued …
Apr 18, 2023 © 2014 Maurice Herlihy 29
Continued …
Eh?
Apr 18, 2023 © 2014 Maurice Herlihy 30
Continued …
Why indeed?
Apr 18, 2023 © 2014 Maurice Herlihy 31
Continued …
Why not?
Apr 18, 2023 © 2014 Maurice Herlihy 32
Continued …
Marketing FAIL
Apr 18, 2023 © 2014 Maurice Herlihy 33
Hard Cases Make Bad Law
• This example does not mean– Every badly written paper has hidden value
Apr 18, 2023 © 2014 Maurice Herlihy 34
Hard Cases Make Bad Law
• This example does not mean– Every badly written paper has hidden value
• But some do
Apr 18, 2023 © 2014 Maurice Herlihy 35
Hard Cases Make Bad Law
• This example does not mean– Every badly written paper has hidden value
• But some do• And some well-written papers
– Have little to say
Apr 18, 2023 © 2014 Maurice Herlihy 36
Hard Cases Make Bad Law
• This example does not mean– Every badly written paper has hidden value
• But some do• And some well-written papers
– Have little to say
• “The race is not always to the swift”– But the smart money bets that way …
Apr 18, 2023 © 2014 Maurice Herlihy 37
Our Mission
• Learn how to come up-to-speed on a research area
• Exact area doesn’t matter (much)– Skill is fungible
• You are always going to need this skill– So start now!
Apr 18, 2023 © 2014 Maurice Herlihy 38
Our Methodology
• Recent conference proceedings– Indicate which topics are hot– Even if the papers themselves are
• Incremental• Cryptic• Or worse!
Apr 18, 2023 © 2014 Maurice Herlihy 39
Our Methodology
• Recent conference proceedings– Indicate which topics are hot– Even if the papers themselves are
• Incremental• Cryptic• Or worse!
• Even the worst papers– Have to cite the best
Apr 18, 2023 © 2014 Maurice Herlihy 40
Detective Work
• Start with a recently published paper– So we know someone cares
Apr 18, 2023 © 2014 Maurice Herlihy 41
Detective Work
• Start with a recently published paper– So we know someone cares
• Skim through it & primary citations– Which citations seem important?
Apr 18, 2023 © 2014 Maurice Herlihy 42
Detective Work
• Start with a recently published paper– So we know someone cares
• Skim through it & primary citations– Which citations seem important?
• Identify area’s primary paper– The one to read if you read only one– First? Best improvement? Best written?
Apr 18, 2023 © 2014 Maurice Herlihy 43
Presentation (35% of Grade)
• Form team of 1, 2, or 3 people• Pick recent paper• Perform “due diligence” on area• Identify one paper that everyone else
– Must read first– Must submit evaluation
• Give presentation• Repeat as needed …
Apr 18, 2023 © 2014 Maurice Herlihy 44
Your Presentation
• Defines problem
• Establishes background
• Identifies primary paper
• Leads discussion
• Identifies open research questions
Apr 18, 2023 © 2014 Maurice Herlihy 45
Participation (10% of Grade)
• Research papers sometimes– Are poorly written,– Make exaggerated or misleading claims– Contain errors or ambiguities (imagine that!).
• I expect students to speak up– Ask questions– Make observations– Apply critical scrutiny.
• It’s no fun without the studio audience!
Apr 18, 2023 © 2014 Maurice Herlihy 46
Paper Evaluations(10% of grade)
• Your name & paper name• Summarize the paper
– no more than five sentences
• Strengths– no more than three, one sentence each
• Weaknesses– no more than three, one sentence each
• Open problems or issues– no more than three sentences
Apr 18, 2023 © 2014 Maurice Herlihy 47
Paper Evaluations(10% of grade)
• Evaluations– will be graded on a scale of 1 to 3.– Default grade is 2.– Insightful reviews get 3– Disappointing reviews get 1.
.
Apr 18, 2023 © 2014 Maurice Herlihy 48
Paper Evaluations(10% of grade)
• Mail evaluations to instructor before start of class in which the paper is presented.
• Late or incomplete evaluations get no credit.
• Must evaluate at least 2/3 of papers presented.
Apr 18, 2023 © 2014 Maurice Herlihy 49
Presentation Evaluations(10% of grade)
• Presenter name(s)• Vision:
– did presenter explain why it matters?
• Style:– did presenter make eye contact, mumble, etc?
• Exposition– confusing slides?
• Q&A– How were questions handled?
Apr 18, 2023 © 2014 Maurice Herlihy 50
Presentation Evaluations(10% of grade)
• Send evaluations to instructor– before Friday 5:00 PM in the week in which the
presentation occurred. No exceptions.– must do 2/3 of presentations
• Be frank, but polite.• Instructor will anonymize and send to
presenters• Exception:
– no need to evaluate instructor’s presentations– too hard to anonymize
Apr 18, 2023 © 2014 Maurice Herlihy 51
Project (30% of grade)
• Requirements same as presentation, except that you:– Work alone, not in a team– Write a term paper, not a presentation.
• Consult the instructor!
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