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Assertions also let you choose subroutines that you think are good candidates for inlining. However, subject to its thresholds, the compiler may reject your choices. Inlining could expand the code so much that increased memory activity would claim back gains made by eliminating the procedure call. At higher optimization levels, the compiler is often capable of making its own choices for inlining candidates, provided it can find the source code for the routine under consideration.

Some compilers support a feature called interprocedural analysis . When this is done, the compiler looks across routine boundaries for its data flow analysis. It can perform significant optimizations across routine boundaries, including automatic inlining, constant propagation, and others.

No side effects

Without interprocedural analysis, when looking at a loop, if there is a subroutine call in the middle of the loop, the compiler has to treat the subroutine as if it will have the worst possible side effects. Also, it has to assume that there are dependencies that prevent the routine from executing simultaneously in two different threads.

Many routines (especially functions) don’t have any side effects and can execute quite nicely in separate threads because each thread has its own private call stack and local variables. If the routine is meaty, there will be a great deal of benefit in executing it in parallel.

Your computer may allow you to add a directive that tells you if successive sub-routine calls are independent:


C$ASSERT NO_SIDE_EFFECTS DO I=1,NCALL BIGSTUFF (A,B,C,I,J,K) END DO

Even if the compiler has all the source code, use of common variables or equivalences may mask call independence.

Manual parallelism

At some point, you get tired of giving the compiler advice and hoping that it will reach the conclusion to parallelize your loop. At that point you move into the realm of manual parallelism. Luckily the programming model provided in FORTRAN insulates you from much of the details of exactly how multiple threads are managed at runtime. You generally control explicit parallelism by adding specially formatted comment lines to your source code. There are a wide variety of formats of these directives. In this section, we use the syntax that is part of the OpenMP (see [link] ) standard. You generally find similar capabilities in each of the vendor compilers. The precise syntax varies slightly from vendor to vendor. (That alone is a good reason to have a standard.)

The basic programming model is that you are executing a section of code with either a single thread or multiple threads. The programmer adds a directive to summon additional threads at various points in the code. The most basic construct is called the parallel region .

Parallel regions

In a parallel region, the threads simply appear between two statements of straight-line code. A very trivial example might be the following using the OpenMP directive syntax:


PROGRAM ONE EXTERNAL OMP_GET_THREAD_NUM, OMP_GET_MAX_THREADSINTEGER OMP_GET_THREAD_NUM, OMP_GET_MAX_THREADS IGLOB = OMP_GET_MAX_THREADS()PRINT *,’Hello There’ C$OMP PARALLEL PRIVATE(IAM), SHARED(IGLOB)IAM = OMP_GET_THREAD_NUM() PRINT *, ’I am ’, IAM, ’ of ’, IGLOBC$OMP END PARALLEL PRINT *,’All Done’END

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
Berger describes sociologists as concerned with
Mueller Reply
what is hormones?
Wellington
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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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