On Sat, Sep 13, 2014 at 6:59 AM, Arthur Silva <arthur...@gmail.com> wrote: > That's not entirely true. CRC-32C beats pretty much everything with the same > length quality-wise and has both hardware implementations and highly > optimized software versions.
For better or for worse CRC is biased by detecting all single bit errors, the detection capability of larger errors is slightly diminished. The quality of the other algorithms I mentioned is also very good, while producing uniformly varying output. CRC has exactly one hardware implementation in general purpose CPU's and Intel has a patent on the techniques they used to implement it. The fact that AMD hasn't yet implemented this instruction shows that this patent is non-trivial to work around. The hardware CRC is about as fast as xxhash. The highly optimized software CRCs are an order of magnitude slower and require large cache trashing lookup tables. If we choose to stay with CRC we must accept that we can only solve the performance issues for Intel CPUs and provide slight alleviation for others. Regards, Ants Aasma -- Cybertec Schönig & Schönig GmbH Gröhrmühlgasse 26 A-2700 Wiener Neustadt Web: http://www.postgresql-support.de -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
