WHAT IS MULTIPROCESSING?

Multiprocessing is the coordinated processing of programs

by more than one computer processor. Multiprocessing is a

general term that can mean the dynamic

assignment of a program to one of two or

more computers working in tandem or can

involve multiple computers working on the

same program atthe same time (in parallel).

With the advent of parallel

processing, multiprocessing is

divided into symmetric

multiprocessing (SMP) and massively parallel

processing (MPP).

 

In symmetric (or "tightly coupled") multiprocessing, the

processors share memory and the I/O bus or data path. A

single copy of the operating system is in charge of all the

processors. SMP, also known as a "shared everything" system,

does not usually exceed 16 processors.

 

In massively parallel (or "loosely

coupled") processing, up to 200 or

more processors can work on the same

application. Each processor has

its own operating system and

memory, but an

"interconnect" arrangement

of data paths allows messages

to be sent between processors. Typically,

the setup for MPP is more complicated,

requiring thought about how to

partition a common database among

processors and how to assign

work among the processors. An MPP

system is also known as a "shared

nothing" system.

Multiprocessing should not be confused with

multiprogramming, or the interleaved execution of

two or more programs by a processor. Today, the

term is rarely used since all but the most

specialized computer operating systems support

multiprogramming. Multiprocessing can also be confused

with multitasking, the management of programs and the

system services they request as tasks that can be interleaved,

and with multithreading, the management of multiple

execution paths through the computer or of multiple users

sharing the same copy of a program.