Jim Apple has posted comments on this change.

Change subject: IMPALA-2809: improve ByteSwap with builtin function or SSE or 
AVX2
......................................................................


Patch Set 3:

(5 comments)

http://gerrit.cloudera.org:8080/#/c/3081/3/be/src/benchmarks/bswap-benchmark.cc
File be/src/benchmarks/bswap-benchmark.cc:

Line 35: //                         Impala               317.2                  
1X
> This benchmark is previously written by Zuo Wang. His idea is demonstrating
Please fix them in the code so future readers will understand.


Line 156:   if (num_bytes == 4) {
> Zuo Wang's idea is implementing a finer-grain level benchmark here. For exa
I think more than comments will be necessary. Can you reduce the repetition by 
refactoring?


http://gerrit.cloudera.org:8080/#/c/3081/3/be/src/util/bit-util.inline.h
File be/src/util/bit-util.inline.h:

Line 140:   const __m128i mask = _mm_set_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 
11, 12, 13, 14,
> I am afraid I can't do this for the initializer _mm_set_epi8/_mm256_set_epi
It might, but it also might create a conditional at the beginning of the 
function.

You might be able to use macros to make this a global that is conditionally 
compiled.


Line 168:   __int128_t part1 = *reinterpret_cast<__int128_t*>(dst);
> Done
This doesn't look done. Did you forget to upload the new version?


Line 189:   if(len >= 32){
> The AVX routine only suits for data length >= 256bit. And the SSE routine o
I'm not sure I agree with you. It checks the lengthand calls ByteSwapScalar for 
the remainder, right?


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Gerrit-MessageType: comment
Gerrit-Change-Id: I392ed5a8d5683f30f161282c228c1aedd7b648c1
Gerrit-PatchSet: 3
Gerrit-Project: Impala
Gerrit-Branch: cdh5-trunk
Gerrit-Owner: Youwei Wang <[email protected]>
Gerrit-Reviewer: Alex Behm <[email protected]>
Gerrit-Reviewer: Jim Apple <[email protected]>
Gerrit-Reviewer: Marcel Kornacker <[email protected]>
Gerrit-Reviewer: Mostafa Mokhtar <[email protected]>
Gerrit-Reviewer: Tim Armstrong <[email protected]>
Gerrit-Reviewer: Youwei Wang <[email protected]>
Gerrit-HasComments: Yes

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