Contents

• CS320/16 Concurrency and Java
• : Preparation -- Chapter 13 -- Concurrency
• : Notes
• : : Concurrency is often faked:
• : : Threads are easier than networks
• : : Ada
• : : Some concurrency bugs are hard to find by testing.
• : : Java Thread
• : : Examples of Concurrency
• : : Missing -- UNIX pipes
• : : Why people do not like concurrency
• : Class Work
• Lab Work
• Next

CS320/16 Concurrency and Java


Table

Prev 15	OO Programming and Java	Chapter 2 section 17 + Java Handout + Chapter 12	lab15 Java101
16	Concurrency and Java	Chapter 13 not sect'n 9	lab16 Java102
Next 17	Exceptions	Chapter 14	lab17 Java103


(Close Table)


Preparation -- Chapter 13 -- Concurrency

1. Study notes below and Chapter 13, but not section 9 (not on the final).
2. You can forget about MIMD/SIMD in this class (not on the final).
3. Don't answer review questions on hardware. They are not on the Final.

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


1. threads
2. semaphores,
3. monitors,
4. deadlocks
5. etc.

Because

1. They turn up all over the place: web sites, data bases, mail handlers, commercial transactions, system administration, etc..
2. They are used in interview questions.
3. They are a part of Java: [ Thread.html ]



Threads are easier than networks

[ 14723 ]

Ada

The ideas in Ada are simple to use
• rendezvous.
• Protected records
• The "message passing" model is simple, reliable, and flexible.



Some concurrency bugs are hard to find by testing.



1. Use simple and sure techniques: message passing and rendezvous.
2. Use logical model checking tools to look for the rare combinations of events that cause bugs.
3. Take CSci556: Formal Methods.



Java Thread



Examples of Concurrency

Look in these directories: [ http://cse.csusb.edu/dick/cs320/sieve/ ] [ http://cse.csusb.edu/dick/cs320/crypto/ ]

Missing -- UNIX pipes



1. Simple to use message passing
2. Also in Java
3. Symbol |
4. Example

    			ls|grep 320



1. For A,B:commands, A|B::command=connects the output of A to the input of B and executes them in parallel.

   Examples

          ls|wc -l

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

          ls|grep 320|wc -l

   list files, filters out those with '320' in the name and counts them.

          grep -l 320 *|wc -l

   counts the number of files with '320' inside them.

          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

   [ 1653418 ]

. . . . . . . . . ( end of section Notes) <<Contents | End>>

Class Work

[ 16q.html ]

Lab Work

Next

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