<< Chapter < Page Chapter >> Page >

Entries that bridge the gap between two areas are welcome. For example, a module about a particular accelerated computing system might describe its accompanying language, and thus fall into both the Parallel Programming Models and Languages and Accelerated Computing categories. However, such modules can only be entered in one category each. To be eligible for awards in multiple categories, the module would need to be divided into appropriate parts, each entered in one category.

Parallel architectures

Today, nearly all computers have some parallel aspects. However, there are a variety of ways that processors can be organized into effective parallel systems. The classic classification of parallel architectures is Flynn’s taxonomy based on the number of distinct instruction and data streams supplied to the parallel processors.

  • Single Instruction, Single Data (SISD) – These are sequential computers. This is the only class that is not a parallel computer. We include it only for completeness.
  • Multiple Instruction, Single Data (MISD) – Several independent processors work on the same stream. Few computers of this type exist. Arguably the clearest examples are fault tolerant systems that replicate a computation, comparing answers to detect errors; the flight controller on the US Space Shuttle is based on such a design. Pipelined computations are also sometimes considered MISD. However, the data passed between stages of the pipeline has been changed, so the “single” data aspect is murky at best.
  • Single Instruction, Multiple Data (SIMD) – A central controller sends the same stream of instructions to a set of identical processors, each of which operates on its own data. Additional control instructions move data or exclude unneeded processors. At a low level of modern architectures, this is often used to update arrays or large data structures. For example, GPUs typically get most of their speed from SIMD operation. Perhaps the most famous large-scale SIMD computer was the Thinking Machines CM-2 in the 1980s, which boasted up to 65,536 bit-serial processors.
  • Multiple Instruction, Multiple Data (MIMD) – All processors execute their own instruction stream, each operating on its own data. Additional instructions are needed to synchronize and communicate between processors. Most computers sold as “parallel computers” today fall into this class. Examples include the supercomputers, servers, grid computers, and multicore chips described above.

Hierarchies are also possible. For example, a MIMD supercomputer might include SIMD chips as accelerators on each of its boards.

Beyond general class, many architectural decisions are critical in designing a parallel computer architecture. Two of the most important include:

  • Memory hierarchy and organization. To reduce data access time, most modern computers use a hierarchy of caches to keep frequently-used data accessible. This becomes particularly important in parallel computers, where many processors mean even more accesses. Moreover, parallel computers must arrange for data to be shared between processors. Shared memory architectures do this by allowing multiple processors to access the same memory. Nonshared memory architectures allot each processor its own memory, and require explicit communication to move data to another processor. A hybrid approach – non-uniform shared memory – places memory with each processor for fast access, but allows slower access to other processors’ memory.
  • Interconnection topology. To communicate and synchronize, processors in a parallel computer need a connection with each other. However, as a practical matter not all of these can be direct connections. Thus is born the need for interconnection networks. For example, interconnects in use today include simple buses, crossbar switches, token rings, fat trees, and 2- and 3-D torus topologies. At the same time, the underlying technology or system environment may affect the networks that are feasible. For example, grid computing systems typically have to accept the wide-area network that they have available.

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 5

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, 2008-'09 open education cup: high performance computing. OpenStax CNX. Oct 28, 2008 Download for free at http://cnx.org/content/col10594/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the '2008-'09 open education cup: high performance computing' conversation and receive update notifications?

Ask