3 ms·

> Is any major software using skiplists as a standard ordered container or map? Java for concurrent navigable maps. https://docs.oracle.com/en/java/javase/21/

• ajross 3y ago
  > Balancing binary search trees suffer from lock contention more than skip lists. Hm... I guess the argument would be that the various list insertions can be independently synchronized? Certainly lookup is going to be a r/w lock or whatever and basically a wash. I vaguely buy that but would want to see numbers. But that said, the hash made of the heap due to the variable size nodes and lack of intrusivity is going to have exactly the opposite effect for any high performance implementation. Maybe Java doesn't play in that sandbox, I guess.
  • _benedict 3y ago
    Garbage collectors are really nice for concurrent data structures, making lock-free algorithms very practical. Java's skip list does not require any locks for write, and requires essentially no synchronisation at all for reads (just suitable platform-dependent memory barriers). I believe reads are also wait free. There is a locality penalty for lookups, although I don't think this is core to skip-lists, just an impracticality of the Java language and how you can use its standard libraries. The variable size of the nodes is not a problem for the Java heap, due to how compacting garbage collectors work.