The well-known idiom to compute a required number of data blocks
of size B to contain data of length d is:
(d + (B-1))/B
The code we use, with ceill(), computes the same value, but does
it in an unorthodox way. This makes a reviewer to doubt himself
and even run tests to make sure we're really computing the
obvious thing.
Apropos the reviewer confusion, the code in Phazr.IO looks weird.
It uses (word_size - hamming_distance) to compute the necessary
number of blocks... but then returns the amount of memory needed
to store blocks of a different size (word_size). We left all of it
alone and return exactly the same values that the old computation
returned.
All these computations were the only thing in the code that used
-lm, so drop that too.
Coincidentially, this patch solves the crash of distro-built
packages of liberasurecode (see Red Hat bug #1454543). But it's
a side effect. Expect a proper patch soon.
Change-Id: Ib297f6df304abf5ca8c27d3392b1107a525e0be0
Currently, there are several implementations of erasure codes that are
available within OpenStack Swift. Most, if not all, of which are based
on the Reed Solomon coding algorithm.
Phazr.IO’s Erasure Coding technology uses a patented algorithm which are
significantly more efficient and improves the speed of coding, decoding
and reconstruction. In addition, Phazr.IO Erasure Code use a non-systematic
algorithm which provides data protection at rest and in transport without
the need to use encryption.
Please contact support@phazr.io for more info on our technology.
Change-Id: I4e40d02a8951e38409ad3c604c5dd6f050fa7ea0
Tim Burke