并發(fā)與并行

【摘要】并行指在同一時(shí)刻锰悼，有多條指令在多個(gè)處理器上同時(shí)執(zhí)行窘俺；并發(fā)指在同一時(shí)刻只能有一條指令執(zhí)行是掰，但多個(gè)進(jìn)程（線程）指令被快速輪換執(zhí)行耍休，使得宏觀上具有多個(gè)進(jìn)程（線程）同時(shí)執(zhí)行的效果羊精。

一抓督、 并發(fā)的定義

維基百科 Concurrent computing is a form of computing in which several computations are executed during overlapping time periods—concurrently—instead of sequentially (one completing before the next starts). This is a property of a system—this may be an individual program, a computer, or a network—and there is a separate execution point or "thread of control" for each computation ("process"). A concurrent system is one where a computation can advance without waiting for all other computations to complete.

百度文庫 并發(fā)（Concurrency），在操作系統(tǒng)中怔昨，是指一個(gè)時(shí)間段中有幾個(gè)程序都處于已啟動運(yùn)行到運(yùn)行完畢之間，且這幾個(gè)程序都是在同一個(gè)處理機(jī)上運(yùn)行祝沸，但任一個(gè)時(shí)刻點(diǎn)上只有一個(gè)程序在處理機(jī)上運(yùn)行。

二仁期、并行的定義

維基百科 Parallel computing is a type of computation in which many calculations or the execution of processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different forms of parallel computing: bit-level, instruction-level, data, and task parallelism. Parallelism has long been employed in high-performance computing, but it's gaining broader interest due to the physical constraints preventing frequency scaling. As power consumption (and consequently heat generation) by computers has become a concern in recent years, parallel computing has become the dominant paradigm in computer architecture, mainly in the form of multi-core processors.

并行計(jì)算是一種同時(shí)進(jìn)行許多計(jì)算或過程執(zhí)行的計(jì)算赊级。大問題往往可以分為小問題橡伞，然后可以同時(shí)解決墨微。并行計(jì)算有幾種不同的形式：位級、指令級、數(shù)據(jù)和任務(wù)并行忘伞。并行性一直被用于高性能計(jì)算中，但由于物理約束阻止了頻率伸縮沙兰，它得到了更廣泛的關(guān)注氓奈。近年來，隨著計(jì)算機(jī)的功耗（以及由此產(chǎn)生的熱量）成為人們關(guān)注的焦點(diǎn)鼎天，并行計(jì)算已成為計(jì)算機(jī)體系結(jié)構(gòu)中的主導(dǎo)范式舀奶，主要以多核處理器的形式出現(xiàn)。

百度文庫 并行（Parallelism）斋射，在操作系統(tǒng)中是指育勺，一組程序按獨(dú)立異步的速度執(zhí)行，不等于時(shí)間上的重疊（同一個(gè)時(shí)刻發(fā)生)罗岖。要區(qū)別并發(fā)涧至。并發(fā)是指：在同一個(gè)時(shí)間段內(nèi)，兩個(gè)或多個(gè)程序執(zhí)行桑包，有時(shí)間上的重疊（宏觀上是同時(shí)南蓬，微觀上仍是順序執(zhí)行）。

三捡多、 并發(fā)與并行

并行指在同一時(shí)刻蓖康，有多條指令在多個(gè)處理器上同時(shí)執(zhí)行；并發(fā)指在同一時(shí)刻只能有一條指令執(zhí)行垒手，但多個(gè)進(jìn)程（線程）指令被快速輪換執(zhí)行蒜焊，使得宏觀上具有多個(gè)進(jìn)程（線程）同時(shí)執(zhí)行的效果

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并發(fā)與并行的區(qū)別