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Maximum speedup of O(log n)

Maximum speedup of O(n / ln n)

  • These “bounds” were based on runtime performance of applications and were not necessarily valid in all cases
  • They reinforced the computer industry’s hesitancy to “get into” parallel processing

3. parallel processors

The machines are the true parallel processors (also called concurrent processors)

These paralle machines fall into Flynn’s taxonomy classes of SIMD and MIMD systems

– SIMD: Single Instruction stream and Multiple Data streams

– MIMD: Multiple Instruction streams and Multiple Data streams

Simd overview

  • Single “control unit” computer and anarray of “computational” computers
  • Control unit executes control-flowinstructions and scalar operations and passes vector instructions to the processor array
  • Processor instruction types:

– Extensions of scalar instructions

Adds, stores, multiplies, etc. become vector operations executed in all processors concurrently

– Must add the ability to transfer vector and scalar data between processors to the instruction set -- attributes of a “parallel language”

  • SIMD Examples

Vector addition

C(I) = A(I) + B(I)

Complexity O(n) in SISD systems for I=1 to n do

C(I) = A(I) + B(I)

Complexity O(1) in SIMD systems

Matrix multiply

A, B, and C are n-by-n matrices

Compute C= AxB

Complexity O(n3) in SISD systems

n2 dot products, each of which is O(n)

Complexity O(n2) in SIMD systems

Perform n dot products in parallel across M the array

Image smoothing

– Smooth an n-by-n pixel image to reduce “noise”

– Each pixel is replaced by the average of itself

and its 8 nearest neighbors

– Complexity O(n2) in SISD systems

– Complexity O(n) in SIMD systems

Pixel and 8 neighbors

Mimd systems overview

  • MIMD systems differ from SIMD ones in that the “lock-step” operation requirement is removed
  • Each processor has its own control unit and can execute an independent stream of


– Rather than forcing all processors to perform the same task at the same time, processors can be assigned different tasks that, when taken as a whole, complete the assigned application

  • SIMD applications can be executed on an MIMD structure

– Each processor executes its own copy of the SIMD algorithm

  • Application code can be decomposed into communicating processes

– Distributed simulations is a good example of a

very hard MIMD application

  • Keys to high MIMD performance are

– Process synchronization

– Process scheduling

  • Process synchronization targets keeping all processors busy and not suspended

awaiting data from another processor

  • Process scheduling can be performed

– By the programmer through the use of parallel language constructs

Specify apriori what processes will be instantiated and where they will be


– During program execution by spawning processes off for execution on available processors.

Fork-join construct in some languages

  • System examples


– Illiac IV

One of the first massively parallel systems 64 processors

– Goodyear Staran: 256 bit-serial processors

– Current system from Cray Computer Corp.uses supercomputer (Cray 3) front end coupled to an SIMD array of 1000s of processors


– Intel hypercube series:

Supported up to several hundred CISC processors

Next-gen Paragon

– Cray Research T3D

Cray Y-MP coupled to a massive array of Dec Alphas

Target: sustained teraflop performance

4. discussions

  • Problems

– Hardware is relatively easy to build

– Massively parallel systems just take massive amounts of money to build

– How should/can the large numbers of processors be interconnected

– The real trick is building software that will exploit the capabilities of the system

  • Reality check:

– Outside of a limited number of high-profile applications, parallel processing is still a“young” discipline

– Parallel software is still fairly sparse

– Risky for companies to adopt parallel strategies, just wait for the next new SISD system.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Computer architecture. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10761/1.1
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