com.github.eprst:murmur3

Fast Murmur3 hash implementation for Java, mostly a fork of yonik work with String-optimized 128-bit implementation and Guava-style sink added. See blog post about the original verion.

There are 3 128-bit versions provided:

• murmurhash3_x64_128 which takes a byte buffer to hash
• murmurhash3_x64_128 which takes a CharSequence and treats it as a UTF-8 encoded string. It doesn't make a quite expensive call to String.getBytes and decodes small chunks on the go instead. It runs in constant memory and uses a 19 element byte buffer which can be provided by the caller to avoid any allocations. See memory charts below for a difference in memory consumption
• murmurhash3_x64_128_ascii which takes a CharSequence and treats it as UTF-8 encoded string with ASCII characters only. Has zero allocations and provides a significant performance boost.

There are no checks made around string decoding operations, so wrong hashes will be generated if a non-ASCII characters are passed to murmurhash3_x64_128_ascii or if murmurhash3_x64_128 receives an illegal UTF-8 string, no errors will be raised.

Performance

Here are results for 128-bit hash on my laptop, run ./gradlew jmh to reproduce. One point is given for hashing 100 random strings, so a score of 38820 for example means 3.8M hashes/sec.

• guava uses com.google.common.hash.Hashing.murmur3_128(0).hashString()
• murmur*Bytes uses murmurhash3_x64_128 passing s.getBytes(StandardCharsets.UTF_8)
• murmur*String calls murmurhash3_x64_128 passing a string directly, it also reuses the 19-byte buffer
• murmurAsciiOptimizedString calls murmurhash3_x64_128_ascii

ACSCII (1-128 characters strings)

Benchmark                                   Mode  Cnt       Score      Error  Units
BenchString128.guavaAscii                  thrpt  100   38820.061 ±  767.128  ops/s
BenchString128.murmurAsciiBytes            thrpt  100   79370.216 ± 1014.949  ops/s
BenchString128.murmurAsciiString           thrpt  100   83249.135 ±  521.336  ops/s
BenchString128.murmurAsciiOptimizedString  thrpt  100  155105.622 ± 1984.475  ops/s

Unicode (1-64 character strings)

Benchmark                            Mode  Cnt      Score     Error  Units
BenchString128.guavaUnicode         thrpt  100  22044.362 ± 228.743  ops/s
BenchString128.murmurUnicodeBytes   thrpt  100  32272.569 ± 635.764  ops/s
BenchString128.murmurUnicodeString  thrpt  100  36704.326 ± 237.645  ops/s

Memory usage

Here are memory usage charts by different versions.

• Guava is com.google.common.hash.Hashing.murmur3_128(0).hashString()
• Bytes is murmurhash3_x64_128 receiving s.getBytes(StandardCharsets.UTF_8)
• String is murmurhash3_x64_128 getting a string directly and having to allocate buf19 on every call
• String, providede buffer is murmurhash3_x64_128 getting a string directly, reusing buf19

Using

Simply copy to your project or get it from maven central.