Difference between revisions of "Thread"
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[[w:thread|Threads of execution]] are a way for a program to split itself into two or more simultaneously (or pseudo-simultaneously) running tasks. Threads and processes differ from one operating system to another, but in general, the way that a thread is created and shares its resources is different from the way a process does. | [[w:thread|Threads of execution]] are a way for a program to split itself into two or more simultaneously (or pseudo-simultaneously) running tasks. Threads and processes differ from one operating system to another, but in general, the way that a thread is created and shares its resources is different from the way a process does. | ||
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Many modern operating systems directly support both time-sliced and multiprocessor threading with a process [[w:scheduler|scheduler]]. The operating system kernel allows programmers to manipulate threads via the system call interface. Some implementations are called a ''kernel thread'', whereas a ''lightweight process'' is a specific type of ''kernel thread'' that shares the same state and information. | Many modern operating systems directly support both time-sliced and multiprocessor threading with a process [[w:scheduler|scheduler]]. The operating system kernel allows programmers to manipulate threads via the system call interface. Some implementations are called a ''kernel thread'', whereas a ''lightweight process'' is a specific type of ''kernel thread'' that shares the same state and information. | ||
| − | = Nodal = | + | == In the Nodal Model == |
| − | In the [[nodal model]], the multithreading time-slicing is achieved by [[w:Time-division multiplexing|time-division multiplexing]] using the [[nodal reduction]] algorithm. [[Loop]]s and threads are formed from | + | In the [[nodal model]], the multithreading time-slicing is achieved by [[w:Time-division multiplexing|time-division multiplexing]] using the [[nodal reduction]] algorithm. [[Loop]]s and threads are formed from {{right}} and {{left}} [[association]]s and a [[focus]] association allows the formation of trees of loops and threads. |
A thread is just a loop which ends with a ''next'' association linking to [[root]]. This has the effect of the thread automatically unhooking from its context after completion because any node with a [[focus]] of [[root]] is considered to have no focus because every [[quanta]] sent to root is a new quanta. Alternatively a context could update its own [[loop]] content dynamically. | A thread is just a loop which ends with a ''next'' association linking to [[root]]. This has the effect of the thread automatically unhooking from its context after completion because any node with a [[focus]] of [[root]] is considered to have no focus because every [[quanta]] sent to root is a new quanta. Alternatively a context could update its own [[loop]] content dynamically. | ||
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If a thread has static structure, then it can appear in many contexts simaltaneously, it's [[parent]] [[association]] will be dynamically maintained by the [[nodal reduction]] algorithm. | If a thread has static structure, then it can appear in many contexts simaltaneously, it's [[parent]] [[association]] will be dynamically maintained by the [[nodal reduction]] algorithm. | ||
| − | + | == See also == | |
| + | *[[Process]] | ||
| + | *[[Loop]] | ||
| + | [[Category:Nodal Concepts]] | ||
Latest revision as of 09:28, 22 July 2011
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Threads of execution are a way for a program to split itself into two or more simultaneously (or pseudo-simultaneously) running tasks. Threads and processes differ from one operating system to another, but in general, the way that a thread is created and shares its resources is different from the way a process does.
Multiple threads can be executed in parallel on many computer systems. This multithreading generally occurs by time slicing, wherein a single processor switches between different threads, in which case the processing is not literally simultaneous, for the single processor is only really doing one thing at a time. This switching can happen so fast as to give the illusion of simultaneity to an end user. For instance, a typical PC today contains only one processor core, but you can run multiple programs at once, such as a word processor alongside an audio playback program; though the user experiences these things as simultaneous, in truth, the processor is quickly switching back and forth between these separate processes. On a multiprocessor or multi-core system, threading can be achieved via multiprocessing, wherein different threads and processes can run literally simultaneously on different processors or cores.
Many modern operating systems directly support both time-sliced and multiprocessor threading with a process scheduler. The operating system kernel allows programmers to manipulate threads via the system call interface. Some implementations are called a kernel thread, whereas a lightweight process is a specific type of kernel thread that shares the same state and information.
In the Nodal Model
In the nodal model, the multithreading time-slicing is achieved by time-division multiplexing using the nodal reduction algorithm. Loops and threads are formed from Right and Left associations and a focus association allows the formation of trees of loops and threads.
A thread is just a loop which ends with a next association linking to root. This has the effect of the thread automatically unhooking from its context after completion because any node with a focus of root is considered to have no focus because every quanta sent to root is a new quanta. Alternatively a context could update its own loop content dynamically.
If a thread has static structure, then it can appear in many contexts simaltaneously, it's parent association will be dynamically maintained by the nodal reduction algorithm.
