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Apparently it does by about 4%. Not quite sure how or why though.
Intel Core i5 3317U (Ivy Bridge) @ 1.7 GHz (turbo 2.4 GHz), Ubuntu 12.04
gcc 4.8, -march=core-avix-i -mavx
Photon Time: 0 hours 0 minutes 2 seconds (2.558 seconds)
using 7 thread(s) with 2.981 CPU-seconds total
Radiosity Time: No radiosity
Trace Time: 0 hours 7 minutes 58 seconds (478.870 seconds)
using 4 thread(s) with 1909.554 CPU-seconds total
gcc 4.8, -march=core-avx-i -msse2
Photon Time: 0 hours 0 minutes 2 seconds (2.607 seconds)
using 7 thread(s) with 3.055 CPU-seconds total
Radiosity Time: No radiosity
Trace Time: 0 hours 8 minutes 18 seconds (498.217 seconds)
using 4 thread(s) with 1986.597 CPU-seconds total
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Le 14/02/2014 07:45, jhu a écrit :
> Apparently it does by about 4%. Not quite sure how or why though.
>
> Intel Core i5 3317U (Ivy Bridge) @ 1.7 GHz (turbo 2.4 GHz), Ubuntu 12.04
>
> gcc 4.8, -march=core-avix-i -mavx
> Photon Time: 0 hours 0 minutes 2 seconds (2.558 seconds)
> using 7 thread(s) with 2.981 CPU-seconds total
> Radiosity Time: No radiosity
> Trace Time: 0 hours 7 minutes 58 seconds (478.870 seconds)
> using 4 thread(s) with 1909.554 CPU-seconds total
>
> gcc 4.8, -march=core-avx-i -msse2
> Photon Time: 0 hours 0 minutes 2 seconds (2.607 seconds)
> using 7 thread(s) with 3.055 CPU-seconds total
> Radiosity Time: No radiosity
> Trace Time: 0 hours 8 minutes 18 seconds (498.217 seconds)
> using 4 thread(s) with 1986.597 CPU-seconds total
There is a few operations (functions in povray) applied to vector (3 or
more double/float) which might enjoy such optimisation.
SSE2 is using only 128 bits of data (2 doubles), whereas AVX is able to
use 256 bits (4 doubles).
The operations are simple, but repeated a lot of time so grabbing a few
cycles per operation gives that change.
--
Just because nobody complains does not mean all parachutes are perfect.
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Le_Forgeron <lef### [at] free fr> wrote:
> Le 14/02/2014 07:45, jhu a écrit :
> > Apparently it does by about 4%. Not quite sure how or why though.
> >
> > Intel Core i5 3317U (Ivy Bridge) @ 1.7 GHz (turbo 2.4 GHz), Ubuntu 12.04
> >
> > gcc 4.8, -march=core-avix-i -mavx
> > Photon Time: 0 hours 0 minutes 2 seconds (2.558 seconds)
> > using 7 thread(s) with 2.981 CPU-seconds total
> > Radiosity Time: No radiosity
> > Trace Time: 0 hours 7 minutes 58 seconds (478.870 seconds)
> > using 4 thread(s) with 1909.554 CPU-seconds total
> >
> > gcc 4.8, -march=core-avx-i -msse2
> > Photon Time: 0 hours 0 minutes 2 seconds (2.607 seconds)
> > using 7 thread(s) with 3.055 CPU-seconds total
> > Radiosity Time: No radiosity
> > Trace Time: 0 hours 8 minutes 18 seconds (498.217 seconds)
> > using 4 thread(s) with 1986.597 CPU-seconds total
>
> There is a few operations (functions in povray) applied to vector (3 or
> more double/float) which might enjoy such optimisation.
>
> SSE2 is using only 128 bits of data (2 doubles), whereas AVX is able to
> use 256 bits (4 doubles).
>
> The operations are simple, but repeated a lot of time so grabbing a few
> cycles per operation gives that change.
The original comparison is a little flawed. Both binaries were compiled with
different versions of gcc. Here's a more apt comparison running on Ubuntu 13.10,
both binaries compiled with gcc 4.8
-march=core-avx-i -mavx
Photon Time: 0 hours 0 minutes 2 seconds (2.590 seconds)
using 7 thread(s) with 3.034 CPU-seconds total
Radiosity Time: No radiosity
Trace Time: 0 hours 8 minutes 9 seconds (489.257 seconds)
using 4 thread(s) with 1954.087 CPU-seconds total
-march=core-avx-i -msse2
Photon Time: 0 hours 0 minutes 2 seconds (2.583 seconds)
using 7 thread(s) with 3.015 CPU-seconds total
Radiosity Time: No radiosity
Trace Time: 0 hours 8 minutes 8 seconds (488.213 seconds)
Result: no significant performance difference.
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