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When you compare this example with a PVM implementation of the same problem, you can see some of the contrasts between the two approaches. Programmers who wrote the same six lines of code over and over in PVM combined them into a single call in MPI. In MPI, you can think “data parallel” and express your program in a more data-parallel fashion.

In some ways, MPI feels less like assembly language than PVM. However, MPI does take a little getting used to when compared to PVM. The concept of a Cartesian communicator may seem foreign at first, but with understanding, it becomes a flexible and powerful tool.

Heat in mpi using broadcast/gather

One style of parallel programming that we have not yet seen is the broadcast/gather style. Not all applications can be naturally solved using this style of programming. However, if an application can use this approach effectively, the amount of modification that is required to make a code run in a message-passing environment is minimal.

Applications that most benefit from this approach generally do a lot of computation using some small amount of shared information. One requirement is that one complete copy of the “shared” information must fit in each of the processes.

If we keep our grid size small enough, we can actually program our heat flow application using this approach. This is almost certainly a less efficient implementation than any of the earlier implementations of this problem because the core computation is so simple. However, if the core computations were more complex and needed access to values farther than one unit away, this might be a good approach.

The data structures are simpler for this approach and, actually, are no different than the single-process FORTRAN 90 or HPF versions. We will allocate a complete RED and BLACK array in every process:


PROGRAM MHEAT INCLUDE ’mpif.h’INCLUDE ’mpef.h’ INTEGER ROWS,COLSPARAMETER(MAXTIME=200) PARAMETER(ROWS=200,COLS=200)DOUBLE PRECISION RED(0:ROWS+1,0:COLS+1),BLACK(0:ROWS+1,0:COLS+1)

We need fewer variables for the MPI calls because we aren’t creating a communicator. We simply use the default communicator MPI_COMM_WORLD . We start up our processes, and find the size and rank of our process group:


INTEGER INUM,NPROC,IERR,SRC,DEST,TAG INTEGER S,E,LS,LE,MYLENINTEGER STATUS(MPI_STATUS_SIZE) INTEGER I,R,CINTEGER TICK,MAXTIME CHARACTER*30 FNAMEPRINT *,’Calling MPI_INIT’CALL MPI_INIT( IERR ) CALL MPI_COMM_SIZE( MPI_COMM_WORLD, NPROC, IERR )CALL MPI_COMM_RANK( MPI_COMM_WORLD, INUM, IERR) CALL MPE_DECOMP1D(COLS, NPROC, INUM, S, E, IERR)PRINT *,’My Share ’, INUM, NPROC, S, E

Since we are broadcasting initial values to all of the processes, we only have to set things up on the master process:


* Start ColdIF ( INUM.EQ.0 ) THEN DO C=0,COLS+1DO R=0,ROWS+1 BLACK(R,C) = 0.0ENDDO ENDDOENDIF

As we run the time steps (again with no synchronization), we set the persistent heat sources directly. Since the shape of the data structure is the same in the master and all other processes, we can use the real array coordinates rather than mapping them as with the previous examples. We could skip the persistent settings on the nonmaster processes, but it doesn’t hurt to do it on all processes:

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, High performance computing. OpenStax CNX. Aug 25, 2010 Download for free at http://cnx.org/content/col11136/1.5
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