mirror_zfs/cmd/ztest
Gvozden Neskovic 37f520db2d Fletcher4: Incremental using SIMD
Combine incrementally computed fletcher4 checksums. Checksums are combined
a posteriori, allowing for parallel computation on chunks to be implemented if
required. The algorithm is general, and does not add changes in each SIMD
implementation.
New test in ztest verifies incremental fletcher computations.

Checksum combining matrix for two buffers `a` and `b`, where `Ca` and `Cb` are
respective fletcher4 checksums, `Cab` is combined checksum, `s` is size of buffer
`b` (divided by sizeof(uint32_t)) is:

Cab[A] = Cb[A] + Ca[A]
Cab[B] = Cb[B] + Ca[B] + s * Ca[A]
Cab[C] = Cb[C] + Ca[C] + s * Ca[B] + s(s+1)/2 * Ca[A]
Cab[D] = Cb[D] + Ca[D] + s * Ca[C] + s(s+1)/2 * Ca[B] + s(s+1)(s+2)/6 * Ca[A]

NOTE: this calculation overflows for larger buffers. Thus, internally, the calculation
is performed on 8MiB chunks.

Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
2016-10-05 16:41:46 +02:00
..
.gitignore Add .gitignore files to exclude build products 2010-01-08 11:35:17 -08:00
Makefile.am Cleanup linking 2016-03-18 13:31:11 -07:00
ztest.c Fletcher4: Incremental using SIMD 2016-10-05 16:41:46 +02:00