====== Week 6 ======

~~NOTOC~~


===== Homework =====

  * UPC exercises 1.1 --- 1.7
    * Assigned: 2/18
    * Due: 2/27


===== Exam Reminder =====

  * Exam next Wednesday, March 6
  * handout: sample questions from a previous exam
  * Review session next Monday, March 4



===== Lecture Notes =====

** Semaphores **

  * Two operations: 
    * wait(s)
      * Traditional: P(s)
      * Definition: <code text> < await (s > 0) s = s - 1; > </code> 
    * signal(s)
      * Traditional: V(s)
      * Definition: <code text> < s = s + 1; > </code> 
  * wait(s) and signal(s) work the same for binary and counting (general) semaphores
    * binary semaphore: value is always either ''1'' or ''0''
    * general semaphore: value is nonnegative

** Class exercise **

  * The Bear and the Honeybees (handout)
    * split binary semaphores
    * technique: pass the baton

  * The Water Molecule Problem (handout)
    * solve using counting semaphores
    * solve using a single mutex 

**Semaphores**

  * Ben-Ari Ch 6
    * slides: {{slides.pdf|PDF}}
      * begin slide 105