You have been subscribed to a public bug: Calculate the checksum of data that is 16 byte aligned and a multiple of 16 bytes.
The first step is to reduce it to 1024 bits. We do this in 8 parallel chunks in order to mask the latency of the vpmsum instructions. If we have more than 32 kB of data to checksum we repeat this step multiple times, passing in the previous 1024 bits. The next step is to reduce the 1024 bits to 64 bits. This step adds 32 bits of 0s to the end - this matches what a CRC does. We just calculate constants that land the data in this 32 bits. We then use fixed point Barrett reduction to compute a mod n over GF(2) for n = CRC using POWER8 instructions. We use x = 32. http://en.wikipedia.org/wiki/Barrett_reduction ** Affects: zlib (Ubuntu) Importance: Undecided Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage) Status: New ** Tags: architecture-ppc64le bugnameltc-136495 severity-low targetmilestone-inin1804 -- zlib: improve crc32 performance on P8 https://bugs.launchpad.net/bugs/1742941 You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to zlib in Ubuntu. -- Mailing list: https://launchpad.net/~touch-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
