On Fri, Aug 11, 2017 at 06:32:37PM +0300, Ivan Kalvachev wrote:
> On 8/10/17, maxime taisant <maximetais...@hotmail.fr> wrote:
> >> From: Ivan Kalvachev <ikalvac...@gmail.com>
> >> On 8/8/17, maxime taisant <maximetais...@hotmail.fr> wrote:
> >> > From: Maxime Taisant <maximetais...@hotmail.fr>
> >> >
> >> > Hi,
> >> >
> >> > Here is some SSE optimisations for the dwt function used to decode
> >> > JPEG2000.
> >> > I tested this code by using the time command while reading a JPEG2000
> >> > encoded video with ffmpeg and, on average, I observed a 4.05% general
> >> > improvement, and a 12.67% improvement on the dwt decoding part alone.
>
> BTW, forgot to tell you that FFmpeg has its own benchmarking macros
> that counts the cpu cycles that it takes for a execution of block of C code.
> Use it (in .c files) like this
>
> #include "libavutil/timer.h"
> {
> START_TIMER
> function();
> STOP_TIMER("function")
> }
>
> The functions would output the results to stderr,
> and they would use the name you provide to them.
> (So you can benchmark more than one thing at a time).
>
> Make sure the function(s) runs a lot per benchmark run.
> The macro would show results at log2 measures.
>
> Do more (3 or 5) separate benchmark runs, since
> the final results always slightly differs. (function could
> be interrupted, and if detected the measurement
> would be discarded/skipped).
>
> Also, try the macro without any function inside,
> so you have the "NULL" function. The stop_timer
> has an instruction fence opcode, that blocks until
> all prior microcodes are executed and this could
> take a while. Your benchmarks could never get
> faster than the NULL function.
>
j2k is already in checkasm; I'd suggest to integrate test(s) for the
functions in that place (tests/checkasm/jpeg2000dsp.c).
make checkasm && tests/checkasm/checkasm --test=jpeg2000dsp --bench
This will make use of the {START,STOP}_TIMER code and provide clean
performance comparisons which you can share here.
--
Clément B.
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