Java / Scala中的高性能字符串散列函数

Question

Looking for a high-performance String hashing functions in Java/Scala - something faster than functions from MurmurHash family, doesn't need to be cryptographically strong, only distribute well.

Any suggestions?

Answer 1

The fastest hashing algorithm that fits the bill presently seems to be xxHash . The lz4-java project contains an implementation ported to Java . I don't know whether the Java implementation has been benchmarked against MurmurHash, though; performance optimizations in C++ don't always port to/from Java. (In particular, xxHash contains more array access, so there could be non-negligible bounds-checking overhead.)

Edit: it looks to me like it uses JNI to call the C++ implementation of xxHash, but JNI overhead is non-negligible, so the performance concerns remain.

However, given that Scala includes a MurmurHash function , and that Java contains a faster default hash (about 2x) that is sorta-reasonably distributed sometimes, one does wonder whether it's really necessary. For instance, scala.util.hashing.MurmurHash3 is about as fast as string creation from an array of bytes, and is twice as fast as that if you give it an array of bytes.

Answer 2

你可以找到非常快速的Java哈希函数实现，BTW帐户内部的String实现（ char[]数组）以最大化速度，这里： https ： //github.com/OpenHFT/Zero-Allocation-Hashing