为什么Java 8中的IntStream.range(0，n)不应该并行? [英] Why IntStream.range(0,n) in Java 8 shouldn't be parallel?

问题描述

我读过一本有关Java 8的书，书上说使用并行流通过 IntStream.range(0，someNumber)获取数字范围可能比顺序的慢...为什么?

I've read a book on Java 8 and the book says that using parallel streams in order to get range of numbers via IntStream.range(0,someNumber) can be slower than sequential one...why is that?

推荐答案

它可能会更慢.默认情况下，您应该始终使用顺序流.与顺序流相比，并行流的开销要高得多，因为它需要在内部进行大量协调工作以及某些簿记活动.

It can be slower. You should always use sequential streams by default. A parallel stream has a much higher overhead compared to a sequential one as it needs a lot of coordination efforts internally along with certain book keeping activities.

如果满足以下条件，则应考虑使用并行的:1.您要处理大量项目，每个项目都需要花费大量时间，并且可以并行化.2.如果您首先遇到性能问题.因此，在尝试并行流或任何其他并发构造之前，黄金法则始终是基准.

You should consider parallel ones if: 1. You have a huge amount of items to process and each item takes substantial time and can be parallelized. 2. If you have for a performance problem in first place. So golden rule is always benchmark before trying parallel streams or any other concurrency constructs.

在您的情况下，如果范围很小，那么在这种情况下，与并行流相关的开销可能会覆盖您应该获得的收益.还要检查这篇文章: http://zeroturnaround.com/rebellabs/java-parallel-streams-for-your-health-bad-for-your-health/

In your case if the range is very small then in that case overhead associated with parallel streams can override the benefit you are supposed to get. Also check this article: http://zeroturnaround.com/rebellabs/java-parallel-streams-are-bad-for-your-health/

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