lz4ultra is a command-line optimal compression utility that produces compressed files in the lz4 format created by Yann Collet.
The tool creates optimally compressed files, like lz4 in optimal compression mode ("lz4hc"), smallLZ4, blz4 and lz4x.
With enwik9 (1,000,000,000 bytes):
Compr.size Tokens Decomp.time (μs, Core i7-6700)
lz4 1.9.2 -12 (favor ratio) 372,443,347 95,698,349 505,804
smalLZ4 1.5 -9 371,680,328 93,172,985 348,018
lz4ultra 1.3.0 (favor ratio) 371,680,323 93,165,899 347,936
lz4 1.9.2 -12 --favor-decSpeed 377,175,400 92,080,802 457,141
lz4ultra 1.3.0 --favor-decSpeed 376,118,079 88,521,993 296,972
The produced files are meant to be decompressed with the lz4 tool and library. While lz4ultra includes a decompressor, it is mostly meant to verify the output of the compressor and isn't as optimized as Yann Collet's lz4 proper.
The tool defaults to 4 Mb blocks with inter-block dependencies but can be configured to output all of the LZ4 block sizes (64 Kb to 4 Mb), to use the LZ4 8 Mb blocks legacy encoding, and to compress independent blocks, using command-line switches.
lz4ultra is developed by Emmanuel Marty with the help of spke.