multithreading

parallel Sharing a single CPU between multiple tasks (or

"threads") in a way designed to minimise the time required to

switch threads. This is accomplished by sharing as much as

possible of the program execution environment between the

different threads so that very little state needs to be saved

and restored when changing thread.

Multithreading differs from multitasking in that threads

share more of their environment with each other than do tasks

under multitasking. Threads may be distinguished only by the

value of their program counters and stack pointers while

sharing a single address space and set of globalvariables. There is thus very little protection of one

thread from another, in contrast to multitasking.

Multithreading can thus be used for very fine-grain

multitasking, at the level of a few instructions, and so can

hide latency by keeping the processor busy after one thread

issues a long-latency instruction on which subsequent

instructions in that thread depend.

A light-weight process is somewhere between a thread and a

full process.

TL0 is an example of a threaded machine language.

Dataflow computation (E.g. Id and SISAL) is an extreme

form of multithreading.

(1997-12-23)