varepsilon / varsync Goto Github PK

s2length in the original rsync  depends on the file size and in most cases 
it is about 2 or 3 bytes, while we use 8 bytes. This leads to decrease in 
speedup. This decrease is significant for small files, but isn't 
noticeable for bigger files.
There are some ways to improve situation (see source code for more 
details).

At this time checksum1 converts one byte from buf to residue modulo 
2^31-1. Unlike that, checksum2 uses PVAL() macro and convert _two_ bytes 
from buf to residue. This gives good performance enhancement.

Checksum2 now converts 4 adjacent bytes to uint32 and then to residue 
modulo 2^31-1. But you can easily generate two different tuples which will 
be converted to different uint32 but to the same residue modulo 2^31-1!