Week 3 Concurrent Programming Abstraction.ppt

7/25/2019 Week 3 Concurrent Programming Abstraction.ppt

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Concurrent Programming CT074-3-2

Concurrent ProgrammingAbstraction


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CT074-3-2 Concurrent Programming 2

Learning Outcomes

At the end of this module, you should be able to do the

following:

1. Explain and apply the fundamental concepts of

concurrency in the design and construction of a

concurrent system using Jaa application.

!. "iscuss the safety aspects of multi threaded system

#. "iscuss the need for encapsulation in concurrent

systems


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The role of abstraction

Dictionary.com:

- the act of consiering something as a general !uality or characteristic"

a#art from concrete realities" s#ecific ob$ects" or actual instances.

- the act of ta%ing a&ay or se#arating' &ithra&al

(abstractionis a techni!ue for managing

com#le)ity of com#uter systems. *t &or%s by

establishing a le+el of com#le)ity on &hich a

#erson interacts &ith the system"su##ressing the more com#le) etails belo&

the current le+el.


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,e+els of abstraction

( ystems an libraries

/ an librariesoften calle A##lication

Program *nterfaces 1AP*efine

com#utational resources that are a+ailable to

the #rogrammer. ou can o#en a file or sen

a message by in+o%ing the #ro#er #roceure

or function call" &ithout %no&ing ho& theresource is im#lemente.


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CT074-3-2 Concurrent Programming


( Programming languages

A #rogramming language enables you to

em#loy the com#utational #o&er of a

com#uter" &hile abstracting a&ay from the

etails of s#ecific architectures.


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( *nstruction sets

6ost com#uter manufacturers esign an buil

families of CPs &hich e)ecute the same

instruction set as seen by the assembly language#rogrammer or com#iler &riter. The members of a

family may be im#lemente in totally ifferent

&aysemulating some instructions in soft&are or

using memory for registersbut a #rogrammercan &rite a com#iler for that instruction set

&ithout %no&ing the etails of the im#lementation.


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( logic gates an im#lementation by

semiconuctors no than%s8

( 9y;< -= electrons in chi#s


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oft&are abstraction.

( ?nca#sulation

( Concurrency


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?nca#sulation

( Data hiing

( Achie+es abstraction by i+iing a soft&are moule into a

#ublic s#ecification an a hien im#lementation.

( #ecification escribes the a+ailable o#erations on a ata

structure or real-&orl moel.

( Detaile im#lementation of the structure or moel is &ritten

&ithin a se#arate moule that is not accessible from the

outsie.

( Changes in internal ata re#resentation an algorithm &ithout

affecting the #rogramming of the rest of the system.( 6oern #rogramming languages irectly su##ort

enca#sulation.



?nca#sulation


11/23CT074-3-2 Concurrent Programming

Pri+ate8

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Concurrency

( Abstraction esigne to ma%e it #ossible

to reason about the ynamic beha+ior of

#rograms.

( There are no im#ortant conce#ts of

concurrency that cannot be e)#laine at

the higher le+el of abstraction.



Concurrent e)ecution as

interlea+ing of atomic

statements



"efinition

( A concurrent #rogram consists of a finite set of

1se!uential #rocesses. The #rocesses are &ritten using

a finite set of atomic statements. The e)ecution of a

concurrent #rogram #rocees by e)ecuting a se!uence

of the atomic statements obtaine by arbitrarily

interlea+ing the atomic statements from the #rocesses. A

com#utation is an e)ecution se!uence that can occur as

a result of the interlea+ing. Com#utations are also calle

scenarios.


15/23CT074-3-2 Concurrent Programming

"efinition

( During a com#utation the control #ointer

of a #rocess inicates the ne)t statement

that can be e)ecute by that #rocess.

?ach #rocess has its o&n control #ointer.

Alternate terms for this conce#t are instruction

#ointer an location counter.



Process Control loc% 1PC



2 #rocesses" # an !

( # #" #2

( ! !" !2

#2 # ! !2 EE


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Tri+ial concurrent #rogram

Tri+ial se!uential #rogram


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CT074-3-2 Concurrent Programming @


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Fustification of the abstraction

( The electrical signals in a com#uter tra+el at the

s#ee of light" about 2 ) 0>mGsec" an the

cloc% cycles of moern CPs are at least one

gigahert


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Fustification of the abstraction

( Ie &ill assume that &e ha+e a JbirKs-

eyeJ +ie& of the global state of the

system" an that a statement of one

#rocess e)ecutes by itself an to

com#letion" before the e)ecution of a

statement of another #rocess

commences.


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L M A

$uestion and Answer %ession

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Week 3 Concurrent Programming Abstraction.ppt