LZ4 is good engineering work, better than Google snappy (zippy) which itself was better than LZO (both have somewhat improved by looking at each other's code since then). The current best general purpose compressor for decompression speed is Oodle Selkie, but it is not open source. I don't if a fast compressor for Oodle Selkie exists - since it was developed for game assets, they don't care about compression speed.
LZ4 is only one of the many variations on the basic principle of the LZ family of algorithms, which is to replace repeated sequences with references to where they were before.
What does amaze me a little, is the fact that the rather more complex Huffman algorithm was published and implemented decades before LZ.
Maybe. It might just be that the tricks it plays matter a lot on newer CPUs, and older fast compressors played older tricks.
I think the ratio of CPU cycles to i/o bandwidth is what really matters. Presumably the optimal tradeoff between CPU throughout and compression ratios depends on that and varies over time.
LZ4 deserves a lot of respect, but it is merely a recent improvement on a very old idea.
It wasn't novel when Lempel and Ziv described it 1977 - the encoding idea itself is almost trivial, and was described before. However, they did prove the conditions under which this compression is asymptotically optimal, which was NOT at all clear or trivial at the time - and it is therefore named after them.
LZ4 is an implementation of the LZ77 idea that optimized run time first and compression ratio second. It is elegant and successful - but it has little novelty.
Not sure what you'd consider suitably documented beyond what is already out there. Not being patented or published in a journal look like positives to me.
