What is fma-rep?

Deduplication filter based on anchor hashing. Technically LZ77, but has no entropy coding, and only longer matches have a chance to be replaced with a reference.

It has much lower memory requirements than lzma, so can be used to compensate lzma’s smaller window/dictionary size.

Examples: Official ISOs from Microsoft for Windows 10 Pro and Office 2016:

Due to large file sizes, and the fact that fma-rep takes a lot less memory than plzma4, it is very useful for large software installation DVDs that have a lot of compressed data already. Best idea is to use large window of fma-rep1 and fast codec, to achieve good compression and yet very fast speed.

Tests

AMD FX8320 with 16GB RAM and SSD

Office 2016 Pro ISO - 1,985,392 kB
.pa (Zstandard2, x64flt, bcj2, fma-rep1) 36s encode, 37s decode - 1,551,741 kB
.rar (Normal) 128s encode, 13s decode, 1,892,471 kB

Windows 10 Pro ISO
.pa (Zstandard2, x64flt, bcj2, fma-rep1) 87s encode, 77s decode - 3,577,849 kB
.rar (Normal) 314s encode, 27s decode - 3,838,188 kB

Sharepoint Server 2013
.rar (Normal) 369s encode, 15s decode - 2,269,782 kB
.zip (WZ 21 Normal) - 47s encode, 13s decode - 2,305, 755 kB
.pa (Zstandard2, x64flt, bcj2, fma-rep1) - 61s encode, 41s decode - 1,955,468 kB