.Open CS320/16 Concurrency and Java
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.Row Prev 15	OO  Programming and Java	Chapter 2 section 17 +  Java  Handout +  Chapter 12  	lab15 Java101
.Row 16	Concurrency and Java	Chapter 13  not sect'n 9	lab16 Java102
.Row Next 17	Exceptions	Chapter 14	lab17 Java103
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.Open Preparation -- Chapter 13 -- Concurrency
  Study notes below and Chapter 13, but not section 9
(not on the final).
  You can forget about MIMD/SIMD in this class
(not on the final).
  Don't answer review questions on hardware. They are not on the Final.
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.Open Notes
. Concurrency is often faked:
One single processor or computer can work as if it had many processors.

All modern operating systems use concurrency.

The introductory definitions and ideas in the book are important.

The various forms of hardware (MIMD and SIMD) and FORTRAN based concurrency
can be ignored.  Take our advanced architecture courses for this
and/or talk to Dr. Gomez.

You need to understand
.List
              threads
              semaphores,
              monitors,
              deadlocks
              etc.
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Because
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  They turn up all over the place: web sites, data bases, mail handlers,
commercial transactions, system administration, etc..
  They are used in interview questions.
  They are a part of Java:
.See http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Thread.html
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. Threads are easier than networks
.See http://software.intel.com/file/14723


. Ada
The ideas in Ada are simple to use
.Set
   rendezvous.
   Protected records
   The "message passing" model is simple, reliable, and flexible.
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. Some concurrency bugs are hard to find by testing.
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   Use simple and sure techniques: message passing and rendezvous.
   Use logical model checking tools to look for the rare combinations 
of
events that cause bugs.
   Take CSci556: Formal Methods.
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. Java Thread
.Image 16Threads.png [Classes Object Thread and interface Runnable]

. Examples of Concurrency
Look in these directories:
.See http://cse.csusb.edu/dick/cs320/sieve/
.See http://cse.csusb.edu/dick/cs320/crypto/

. Missing -- UNIX pipes
.List
    Simple to use message passing
    Also in Java
    Symbol |
    Example
.As_is 			ls|grep 320
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For A,B:commands, A|B::command=`connects the output of A to the input of B and executes them in parallel`.

Examples
.As_is       ls|wc -l
lists files and counts them. (ls =list, wc -l = count lines)

.As_is       ls|grep 320|wc -l
list files, filters out those with '320' in the name and counts them.

.As_is       grep -l 320 *|wc -l
counts the number of files with '320' inside them.

.As_is       ps -elf|grep $USER
lists all processes and filters out those with your name in them... 
including
the two processes 'ps -elf' and 'grep'.

. Why people do not like concurrency
.See https://joindiaspora.com/posts/1653418

.Close Notes
. Class Work
.See http://www/dick/cs320/16q.html
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. Lab Work
.See ./lab/16.html
. Next
.See ./17.html