什么时候ConcurrentSkipListSet有用？ [英] When is a ConcurrentSkipListSet useful?
问题描述
ConcurrentSkipListSet 和 ConcurrentSkipListMap 在需要多个线程访问的排序容器时很有用。这些实质上是TreeMap和TreeSet的并发代码的等价物。
JDK 6的实现基于高性能动态无锁哈希表和基于列表的集由迈克尔·迈克尔在IBM，这表明您可以实现大量使用比较和交换（CAS）操作的跳过列表上的操作。这些是无锁的，所以你不用担心使用这些类时 synchronized （对于大多数操作）的开销。
目前没有红黑树基于并发的Map /在Java中设置实现。我看过文献，发现了一个情侣 论文显示并发的RB树优于跳过列表，但是许多这些测试都是使用事务内存完成的，目前在任何主要架构的硬件中都不支持。
我假设JDK的人在这里跳过列表，因为实现是众所周知的，因为使其无锁是简单和便携（使用CAS）。如果有人关心澄清，请做。我很好奇。
I just saw this data-structure on the Java 6 API and I'm curious about when it would be an useful resource. I'm studying for the scjp exam and I don't see it covered on Kathy Sierra's book, even though I've seen mock exam questions that mention it.
ConcurrentSkipListSet and ConcurrentSkipListMap are useful when you need a sorted container that will be accessed by multiple threads. These are essentially the equivalents of TreeMap and TreeSet for concurrent code.
The implementation for JDK 6 is based on High Performance Dynamic Lock-Free Hash Tables and List-Based Sets by Maged Michael at IBM, which shows that you can implement a lot of operations on skip lists atomically using compare and swap (CAS) operations. These are lock-free, so you don't have to worry about the overhead of synchronized (for most operations) when you use these classes.
There's currently no Red-Black tree based concurrent Map/Set implementation in Java. I looked through the literature a bit and found a couple papers that showed concurrent RB trees outperforming skip lists, but a lot of these tests were done with transactional memory, which isn't supported in hardware on any major architectures at the moment.
I'm assuming the JDK guys went with a skip list here because the implementation was well-known and because making it lock-free was simple and portable (using CAS). If anyone cares to clarify, please do. I'm curious.
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