Table of Contents
1 Overview of this week
This week, we will learn thread programming, how debugging thread programs
using testing tools can miss bugs, and how formal verification tools
can help locate these bugs with assurance.
Formal verification tools are also subject to exponential blow-ups, although
they often try to avoid wasted searches.
They give you measurable
coverage according to precise coverage criteria.
However, you must use formal verification tools with care -- else they
will also explode.
In particular,
much like with testing, you must downscale your problems
before you attempt to formally verify.
By ``downscale'' we mean: dial down the values of the #define
constants, and also make suitable adjustments to the overall code.
Without this, all your formal verification attempts will bite the dust!
With some downscaling, formal verification tools can be your best friends!
How much downscaling is needed?
You should discover that using your engineering acumen!!
There is no free lunch.
We won't automatically find your bugs!
We only help you find them.
2 Assignment
Assignment 3 (due 2/10):
Please DO NOT post your solutions WHERE INDICATED. Instead, FOR THOSE PROBLEMS,
please keep a webpage containing your solutions in PDF form, and please
email me the web URL.
For all other questions, do post the solutions / discussions online!
Those are very valuable and all of us get to learn from each other.
-
5%:
- Try to gcc -lpthread -lssl file.c on the
Code examples courtesy of LLNL, Blaise Barney
watch-count-small-buggy.c, watch-count-small.c, bug1-small.c, bug1fix-small.c
Run the resulting a.out. Did you encounter any bugs?
- 10%:
- Key for discussions: bug1ix-small
Does bug1fix-small.c really fix the bug?
Use Inspect to find out.
Also run Inspect on the other examples. (Also demo-ed in class.)
- 5%:
Key for discussions: prodcons under gcc
Try to gcc -lpthread -lssl prodcons.c and run the
a.out. Can you find any bugs?
- 30%:
- Please do not post discussions on this question. Put it on the PDF on your URL, instead.
Formally verify the prodcons.c code using Inspect.
Exactly describe the bug.
- 20%:
- Please do not post discussions on this question. Put it on the PDF on your URL, instead.
Fix the bug in prodcons.c and re-verify using Inspect.
- 10%:
- Key for discussions: Boehm -- Threads as a Library
Read and summarize (in a page) ``Threads Cannot be Implemented as a Library'' by Boehm
http://www.eng.utah.edu/~cs5966/LECTURES/Week4/boehm-threads-as-a-library.pdf
- 10%:
- Key for discussions: Boehm -- Reordering Pthread-Style Locks
Read and summarize (in a page) ``Reordering Constraints for Pthread-Style Locks'' by Boehm
http://www.eng.utah.edu/~cs5966/LECTURES/Week4/boehm-reordering-pthread-style-locks.pdf
- 5%:
- Please do not post! Put it on URL.
Code-up the Sieve program in Boehm's Threads as a Library paper (see above) using Pthreads/C and show that indeed you are able to
get some speed-up on our machines.
- 5%:
- Please do not post! Put it on URL.
Redo the above part using Cilk (must be easier to do time measurements using Cilk).
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