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In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. [1] In many cases, a thread is a component of a process .
From the software standpoint, hardware support for multithreading is more visible to software, requiring more changes to both application programs and operating systems than multiprocessing. Hardware techniques used to support multithreading often parallel the software techniques used for computer multitasking .
Micro-threading is a software-based threading framework that creates small threads inside multi-core or many-core processors. Each core may have two or more tiny threads that utilize its idle time. It is like hyper-threading invented by Intel or the general multi-threading architecture in modern micro-processors.
Intel reintroduced Hyper-Threading with the Nehalem microarchitecture, after its absence on the Core microarchitecture. AMD Bulldozer microarchitecture FlexFPU and Shared L2 cache are multithreaded but integer cores in module are single threaded, so it is only a partial SMT implementation. [9] [10] AMD Zen microarchitecture has 2-way SMT.
In both cases, the features must be part of the language syntax and not an extension such as a library (libraries such as the posix-thread library implement a parallel execution model but lack the syntax and grammar required to be a programming language).
Temporal multithreading is one of the two main forms of multithreading that can be implemented on computer processor hardware, the other being simultaneous multithreading. The distinguishing difference between the two forms is the maximum number of concurrent threads that can execute in any given pipeline stage in a given cycle .
Like preemptive multitasking, each thread of execution is assigned its own program counter and other hardware registers (each thread's architectural state). A barrel processor can guarantee that each thread will execute one instruction every n cycles, unlike a preemptive multitasking machine, that typically runs one thread of execution for tens ...
Software libraries can provide certain thread-safety guarantees. [5] For example, concurrent reads might be guaranteed to be thread-safe, but concurrent writes might not be. Whether a program using such a library is thread-safe depends on whether it uses the library in a manner consistent with those guarantees.