CSE 128 Spring
Class meets Tuesdays
Thursdays in Sequoyah 147 from 2 to 3:20pm
section Mondays in CSB 002 from 4 to 4:50pm
Office hours MW 11-12 in my office (APM 4824) or by appointment..
TA Xianan Zhang.
Office hours W 1-3 in EBU-1 6307A.
Wednesday, June 9 3-6 PM
The exam will be held in EBU 1-3327 (we've reserved the timeslot for
the 26 Sun workstations in one part of the room)
Concurrency is more
than semaphores, threads, and synchronized classes in Java. Concurrency
is a characteristic of systems including distributed systems, computer
hardware, and physical systems. The aim of this class is to give you
some tools to help you think about concurrency and to come up with
concurrent programs and systems that are more likely to be correct.
One of the main
themes of this course is teaching you how to specify a concurrent
system and show that it implements properties that you desire. You will
learn a specification language, TLA+, that can be mechanically checked
using a model
We will cover
the following topics:
Your grade in
this class will be determined by your performance in five homeworks
(25% total), a class project (50%), and a closed-book and notes final
- TLA, TLA+, and TLC.
- Refinement mappings
- Two phase handshake protocol
- Grain of atomicity
- Fairness and liveness
- Threads and semaphores in Java
- Producer-Consumer synchronization
- Java implementation
- Shift register
- Another approach to producer-consumer.
- Revisiting grain of atomicity
- Multiclient server systems
- Mutual exclusion
- Monitors as multiclient server systems
- Monitors in Java
- Resource Allocation
- Nonatomic operations and memory models
- The impact on writing concurrent programs.
- The Bakery algorithm
- Sequentially consistent memory
- Weak lazy caching
- Distributed multiclient servers
Please turn in your homework by emailing it to firstname.lastname@example.org.
turn in any .tla/.cfg/.java files as attachments to a message that
contains any explanation or other text answers.
- Due April
8, 2004 at 2pm: Problem 1.1 and Problem 1.2 in notes.
- Due April 22, 2004 at 2pm:
Problems 2.3. 2.4, 2.6. 2.8 and 2.9 in notes. Comments and corrections here.
- Due May 6, 2004 at 2pm:
Problems 3.4, 3.5, 3.7 and 3.8 in notes. Comments and corrections here.
May 20 May 27, 2004 at 2pm:
Problems 4.8 and 4.13 in notes. Comments and corrections here.
- Due June 10, 2004 at 2pm:
Problem 4.14 in notes.
can work on your class project either by yourself or with one other
person. If you do a project with another person, please explain in your
report how you divided up the work. In the project descriptions, I
give some ideas of how you might extend the project for two people,
but these are only ideas. You can decide for youself on how to extend
or change the project to accomodate two people.
The written part of the project will be due on
Monday Tuesday morning (12:01
AM) of Week 10. This should consist of a paper that describes the
problem you considered and your solution. You should also turn in the
files for your specification and your implementation.
I will also schedule a brief meeting with you during
Week 10 for you to give us a presentation of your project.
Please choose one of the following topics for your project:
- A weak
binary semaphore is a binary
semaphore with weak fairness. Thus, if you have two processes using a
single binary semaphore to protect a critical region, it is possible
for one process to never enter the critical region: it could infinitely
often find itself in contention with the other process, and the other
process could always win the contention. An example of a weak binary
semaphore is one implemented with test
Implement n process mutual exclusion using
only weak binary semaphores. The number of processes n is a parameter of the system.
Show your solution is correct using TLA+. Then, write a Java program
that implements a test and set class,
and then implements your solution. Your program should create a set of
threads that repeatedly try to enter the critical section, and that
perform some simple diagnostics to determine whether the solution
violates safety and fairness.
For two people working on this project, you might try to do an actual
implementation of binary semaphores using test and set (or whatever
instruction you find on the hardware you choose to use). You could then
do a real implementation, perhaps in C.
- Barrier synchronization is a
concurrency construct that allows a (fixed) set of threads to block
until all threads have arrived at the barrier. If barrier(n) is the construct, then a thread
blocks when it executes barrier(n) until all n threads have executed barrier(n). Then, eac blocked thread
unblocks, but block again if it again executes barrier(n).
First, come up with a
lower bound on the number of semaphores that are required to implement
barrier synchronization. Your argument can be informal. Then, devise a
solution that uses as few semaphores as you can - ideally, the number
you showed to be a lower bound. Use TLA+ to show that your solution
does indeed implement barrier synchronization.
For two people working on this project, you might try to examine the
implementation of barrier synchronization in a real multiprocessor
system, and compare it with your semaphore-based solution.
four processes that communicate by sending messages to each other. You
can assume that if a process p
sends a message to process q
at time t, then q will receive the message by time t +
D for some known constant D.
Each process i has a value i.input.
Your goal is to design a protocol such that each correct process i determines a value i.output where:
- For any
two nonfaulty processes i and
j, i.output = j.output.
- If, for
all processes i, i.input = v, then each nonfaulty process j sets j.output to v.
No more than one
process can be faulty. A faulty process can send any message it wishes.
For example, it can tell one correct process that its input value was
tell another process that its input value was 17. It can also fail to
send some messages, or simply stop running.
Show that your protocol is correct using TLA+. Then, implement your
protocol. You will need to define a message
class that allows a process on one machine to send a message to
another process, on the same or a different machine. Choose a value of D that is reasonable for your
experimental setup. Write a demonstration program that illustrates your
protocol in action where one process is faulty.
For two people working on this project, you might try to built your
protocol where there are seven
processes and up to two of
them can be faulty.
Discussion section 1
Discussion section 2