Update to pzip, with background and more spec

concurrency-pzip/README.md

@@ -12,6 +12,21 @@ There are three specific objectives to this assignment:
 * To learn how to parallelize a program.
 * To learn how to program for high performance.
 
+## Background
+
+To understand how to make progress on this project, you should first
+understand the basics of thread creation, and perhaps locking and signaling
+via mutex locks and condition variables. These are described in the following
+book chapters:
+
+- [Intro to Threads](http://pages.cs.wisc.edu/~remzi/OSTEP/threads-intro.pdf)
+- [Threads API](http://pages.cs.wisc.edu/~remzi/OSTEP/threads-api.pdf)
+- [Locks](http://pages.cs.wisc.edu/~remzi/OSTEP/threads-locks.pdf)
+- [Using Locks](http://pages.cs.wisc.edu/~remzi/OSTEP/threads-locks-usage.pdf)
+- [Condition Variables](http://pages.cs.wisc.edu/~remzi/OSTEP/threads-cv.pdf)
+
+Read these chapters carefully in order to prepare yourself for this project.
+
 ## Overview
 
 First, recall how `zip` works by reading the description
@@ -40,6 +55,10 @@ least) the following issues:
     can be done in parallel, and what must be done serially by a single
     thread, and design your parallel zip as appropriate.
 
+    One interesting issue that the "best" implementations will handle is this:
+    what happens if one thread runs more slowly than another? Does the
+    compression give more work to faster threads? 
+
 - **How to determine how many threads to create.** On Linux, this means using
     interfaces like `get_nprocs()` and `get_nprocs_conf()`; read the man pages
     for more details. Then, create threads to match the number of CPU
@@ -58,6 +77,7 @@ least) the following issues:
     into the address space, you can then access bytes of the input file via
     pointers and do so quite efficiently. 
 
+
 ## Grading
 
 Your code will first be measured for correctness, ensuring that it zips input