lbzip2 is an independent, multi-threaded implementation of bzip2 which
can process standard bz2 files in parallel.  It uses POSIX threading
model (pthreads), which allows it to take full advantage of the symmetric
multiprocessing (SMP) systems.  It has been proven to scale linearly, even
to over one hundred processor cores, and commonly considered the fastest
SMP (and uniprocessor) bzip2 compressor and decompressor.

lbzip2 is fully compatible with bzip2 -- both at file format and command
line level.  Files created by lbzip2 can be decompressed by all versions
of bzip2 and other software supporting bz2 format.  This makes lbzip2 a
drop-in replacement for bzip2.