Immutable, in-memory B-Trees for Scala

Current status: proof-of-concept.

Performance is in the same ball-park as the standard Red-Black Tree used by Scala's TreeSet implementation, but gets better when there are many elements in the tree, due to higher memory efficiency.

Overall the B-Tree uses about 1/5th the memory of a Red-Black Tree (assuming a minimum of 16 values in leaves).

Benchmarks

Start sbt with something like:

$ SBT_OPTS="-Xms1G -Xmx1G -XX:+UseCompressedOops -XX:+UseSerialGC -XX:+TieredCompilation" sbt test:console

Then run a benchmark:

scala> scalax.collection.immutable.BTreeSetThyme.insertShuffled()

The benchmark make use of the excellent Thyme library.

Copyright

Copyright (c) 2013 Zilverline B.V. See LICENSE for details.