====== Week 9 ======

~~NOTOC~~

===== Monitors (cont'd) =====

**Assignment 4: Dining Java Philosophers**

  * Assigned: Mon, Oct 19
  * Due: Fri, Oct 30
  * {{ diningjavaphils.pdf |PDF}}
  * Questions?

**Notes**
  * Ben-Ari slides: {{slides.pdf|PDF}}
  * My monitor notes: {{:courses:cs377-201603:cs377-monitors.pdf|PDF}}
  * Monitor state transition diagram: {{monitor-state-diagram.pdf |PDF}} \\ \\ 

**Class participation with monitors:**
  * The One-Lane Bridge problem:<code text>
Cars coming from the north and south arrive at a 
one-lane bridge. Cars heading in the same direction 
can cross the bridge at the same time, but cars 
heading in opposite directions cannot.</code>
  * can we find a way to be safe, fair, and efficient?
  * handout: {{onelanebridgemonitor-1up.pdf |PDF}} (with thanks to Charlie Hughes!)

===== Channels, CSP, and Go =====

  * CSP and Go!
  * Hoare's 1978 CSP paper: https://spinroot.com/courses/summer/Papers/hoare_1978.pdf
    * Go implementation of examples from paper: https://godoc.org/github.com/thomas11/csp
  * Rob Pike's Google I/O 2012 - Go Concurrency Patterns: https://youtu.be/f6kdp27TYZs
  * Peter Welch's slides introducing CSP and occam-pi (but we will use Go this semester!)
    * [[courses:cs377-202001:welch-lectures:top|Occam-pi Lecture Notes]]
    * even though we won't be programming in occam-pi, I want to give you a flavor of it
    * because: 
      * ultimate lightweight processes!
      * composition! 
    * **//Objects Considered Harmful//** (slide 27 of [[https://www.cs.vassar.edu/_media/courses/cs377-202001/welch-lectures/motivation.pdf|motivation.pdf]] slides)
    * **//Legoland://** (slide 83-end of [[https://www.cs.vassar.edu/_media/courses/cs377-202001/welch-lectures/basics.pdf|basics.pdf]]) \\ \\ 

  * Demo and codewalk of [[csp-dining-phils|csp-dining-philosophers.go]]
    * Go language features highlighted:
      * channels
      * select
    * Design basis for solution in Go: go routines (processes)
      * room (communicates with philosophers over channels)
        * for philosophers to enter/leave -- at most 4 at a time to prevent deadlocking, 5th philosopher blocks 
      * forks (communicate with philosophers over channels)
      * philosophers (communicate with forks over channels) \\ \\