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License: BSD 2-Clause "Simplified" License
Positional Population Count for Go
License: BSD 2-Clause "Simplified" License
Hi Robert,
Thanks for persisting optimizing this great package.
I found that bit matrix transpositions slows down counting (100K buffer and others) since d24d616b (Add new count8 variant using bit matrix transpositions). I know you're creating a general framework to port to other platform, a little performance reduction may be tolerated.
I add some tests with few bytes, which I use in my cases.
Current version: d6e39e5
BenchmarkCount8/avx2/32-16 74935256 15.5 ns/op 2066.51 MB/s
BenchmarkCount8/avx2/64-16 55956423 20.3 ns/op 3153.58 MB/s
BenchmarkCount8/avx2/128-16 37906530 29.8 ns/op 4302.12 MB/s
BenchmarkCount8/avx2/256-16 24502731 50.8 ns/op 5038.58 MB/s
BenchmarkCount8/avx2/512-16 31988312 37.8 ns/op 13560.77 MB/s
BenchmarkCount8/avx2/1000-16 20510130 61.9 ns/op 16148.71 MB/s
BenchmarkCount8/avx2/10000-16 2245747 524 ns/op 19087.36 MB/s
BenchmarkCount8/avx2/100000-16 248845 4595 ns/op 21761.87 MB/s
Starting using bit matrix transpositions: 41dbbc5 (speedup after d24d616b)
BenchmarkCount8/avx2/32-16 100472971 13.2 ns/op 2431.84 MB/s
BenchmarkCount8/avx2/64-16 66744648 17.9 ns/op 3568.20 MB/s
BenchmarkCount8/avx2/128-16 42810946 28.3 ns/op 4530.39 MB/s
BenchmarkCount8/avx2/256-16 20535319 56.7 ns/op 4516.74 MB/s
BenchmarkCount8/avx2/512-16 33010789 37.1 ns/op 13811.14 MB/s
BenchmarkCount8/avx2/1000-16 21271256 56.3 ns/op 17774.12 MB/s
BenchmarkCount8/avx2/10000-16 2517070 447 ns/op 22377.79 MB/s
BenchmarkCount8/avx2/100000-16 296733 4059 ns/op 24637.18 MB/s
Old but fast way:
677120e
BenchmarkCount8/avx2/32-16 181525946 7.16 ns/op 4466.72 MB/s
BenchmarkCount8/avx2/64-16 112528216 10.5 ns/op 6069.95 MB/s
BenchmarkCount8/avx2/128-16 63801217 18.7 ns/op 6836.36 MB/s
BenchmarkCount8/avx2/256-16 40247318 29.1 ns/op 8795.27 MB/s
BenchmarkCount8/avx2/512-16 38962676 28.7 ns/op 17869.65 MB/s
BenchmarkCount8/avx2/1000-16 20517376 57.8 ns/op 17289.99 MB/s
BenchmarkCount8/avx2/10000-16 2644093 432 ns/op 23135.55 MB/s
BenchmarkCount8/avx2/100000-16 295675 3913 ns/op 25554.00 MB/s
Consider:
// B:A = A+B+C
#define CSA(A, B, C, D) \
MOVOA A, D \
PAND B, D \
PXOR B, A \
MOVOA A, B \
PAND C, B \
PXOR C, A \
POR D, B
vs
// B:A = A+B+C
#define CSA(A, B, C) \
PXOR C, B \
PXOR A, C \
PXOR B, A \
POR C, B \
PXOR A, B
The C
input must be ready 1 cycle earlier.
This is mainly for SSE2 platforms. AVX2/NEON instructions have non-destructive 3-operand forms.
Some architectures have "free" "mov elimination" which makes this change hard to benchmark.
IIRC, a problem I was having before was about how the compiler was merging a load with an xor instruction...
xor r1, [mem]
vs
load r2, [mem]
xor r1, r2
Not sure if this would be an issue with GoLang Assembly.
======
This issue is not important, feel free to close this out, just one of my pet projects.
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