[FFmpeg-devel] [PATCH] avcodec/huffman: replace qsort with AV_QSORT

[Ganesh Ajjanagadde]

On Thu, Oct 22, 2015 at 9:28 PM, Timothy Gu <timothygu99 at gmail.com> wrote:
> On Thu, Oct 22, 2015 at 5:01 PM Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> wrote:
>>
>> Sample benchmark (x86-64, Haswell, GNU/Linux), fraps-v2 from FATE:
>> new:
>> 280110 decicycles in qsort,       1 runs,      0 skips
>> 268260 decicycles in qsort,       2 runs,      0 skips
>>
>> old:
>> 1469910 decicycles in qsort,       1 runs,      0 skips
>>  952950 decicycles in qsort,       2 runs,      0 skips
>
>
> Usually it takes more than 2 runs to make sure something is faster than the
> other (try -stream_loop 10000 on the input).

In this case the gain should be obvious due to inlining. Nevertheless,
here are new numbers. I chose vp6 for two reasons:
1. Above was for fraps-v2, giving vp6 for more "completeness".
2. stream_loop throws errors: Error while decoding stream #0:0:
Invalid data found when processing input for fraps-v2.

Here they are:
vp6 (old):
  78930 decicycles in qsort,       1 runs,      0 skips
  45330 decicycles in qsort,       2 runs,      0 skips
  27825 decicycles in qsort,       4 runs,      0 skips
  17471 decicycles in qsort,       8 runs,      0 skips
  12296 decicycles in qsort,      16 runs,      0 skips
   9554 decicycles in qsort,      32 runs,      0 skips
   8404 decicycles in qsort,      64 runs,      0 skips
   7405 decicycles in qsort,     128 runs,      0 skips
   6740 decicycles in qsort,     256 runs,      0 skips
   7540 decicycles in qsort,     512 runs,      0 skips
   9498 decicycles in qsort,    1024 runs,      0 skips
   9938 decicycles in qsort,    2048 runs,      0 skips
   8043 decicycles in qsort,    4095 runs,      1 skips

vp6 (new):
  15880 decicycles in qsort,       1 runs,      0 skips
  10730 decicycles in qsort,       2 runs,      0 skips
  10155 decicycles in qsort,       4 runs,      0 skips
   7805 decicycles in qsort,       8 runs,      0 skips
   6883 decicycles in qsort,      16 runs,      0 skips
   6305 decicycles in qsort,      32 runs,      0 skips
   5854 decicycles in qsort,      64 runs,      0 skips
   5152 decicycles in qsort,     128 runs,      0 skips
   4452 decicycles in qsort,     256 runs,      0 skips
   4161 decicycles in qsort,     511 runs,      1 skips
   4081 decicycles in qsort,    1023 runs,      1 skips
   4072 decicycles in qsort,    2047 runs,      1 skips
   4004 decicycles in qsort,    4095 runs,      1 skips

>
> Timothy