REP is an alternative implementation of rzip algorithm by Bulat Ziganshin used in his FreeArc archiver as preprocessor for LZMA/Tornado compression algorithms. In FreeArc, REP finds large-distance matches and then LZMA compress the remaining data. For example, on computer with 2 GB RAM, REP finds matches that is at least 512 bytes long at the distances up to 1 GB, and then LZMA finds any remaining matches at the distances up to 128 MB. So, working together, they provide the best compression possible on 2 GB RAM budget. Being optimized for stream decompression and collaborative work with LZMA, REP has some differences from the original RZIP implementation. First, by default it finds only matches that are 512+ byte long, since benchmarking proved that this is optimal setting for overall REP+LZMA compression. Second, it uses a sliding dictionary that's about 1/2 RAM long, so decompression doesn't need to reread data from decompressed file. REP's advantage is its multiplicative rolling hash that is both quick to compute and has near-ideal distribution. Larger minimal match length (512 bytes compared to 32 bytes in rzip) allowed for additional speed optimizations, so that REP provides very fast compression (about 200 MB/s on Intel i3-2100). SREP SREP (SuperREP) is an implementation of Tridgell's idea of LZ compressor that doesn't store its dictionary in RAM, using instead SHA1 hashes of processed blocks to compare their contents. It allows the program to compress files that are about 10x larger than RAM available. Decompression performed either by reading data from decompressed part of file, or by storing in the memory future matches (future-LZ compression algorithm). Of course, future-LZ compression requires 2 passes over input file but decompression needs tiny memory. In one experiment, 22 GB file compressed with minimum match length of 512 bytes and full 22 GB dictionary required just 2 GB of RAM for decompression. See also List of archive formats, Comparison of archive formats List of file archivers, Comparison of file archivers References External links rzip lrzip — an improvement to rzip allowing the second stage bzip2 reduction to be replaced by LZMA, LZO, or no second-stage (raw, dictionary-only compression). The author is Con Kolivas who states that 'lrzip' stands for 'Long Range ZIP'. rzip64 — a parallel improvement to 'rzip' with stop-and-go mode from Kay Gorontzi. REP — improved RZIP implementation optimized for use together with LZMA SREP — the first LZ compressor that uses