Re: [PATCH] Hex-coding optimizations using SVE on ARM.

On Sat, Jan 11, 2025 at 3:46 AM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
>
> I was able to get auto-vectorization to take effect on Apple clang 16 with
> the following addition to src/backend/utils/adt/Makefile:
>
> encode.o: CFLAGS += ${CFLAGS_VECTORIZE} -mllvm -force-vector-width=8
>
> This gave the following results with your hex_encode_test() function:
>
> buf | HEAD | patch | % diff
> -------+-------+-------+--------
> 16 | 21 | 16 | 24
> 64 | 54 | 41 | 24
> 256 | 138 | 100 | 28
> 1024 | 441 | 300 | 32
> 4096 | 1671 | 1106 | 34
> 16384 | 6890 | 4570 | 34
> 65536 | 27393 | 18054 | 34

We can do about as well simply by changing the nibble lookup to a byte
lookup, which works on every compiler and architecture:

select hex_encode_test(1000000, 1024);
master:
Time: 1158.700 ms
v2:
Time: 777.443 ms

If we need to do much better than this, it seems better to send the
data to the client as binary, if possible.

--
John Naylor
Amazon Web Services