t: Re: Performance of floating point instructions
Hi,
(I resurrected this old thread because there was on meego-dev
mailing list a comment about possibility for RunFast float mode
being enabled by default on MeeGo...)
ext Alberto Mardegan wrote:
> Eero Tamminen wrote:
>> Hamalainen Kimmo (No
On 10/29/2010 12:14 PM, Eero Tamminen wrote:
Hi,
(I resurrected this old thread because there was on meego-dev
mailing list a comment about possibility for RunFast float mode
being enabled by default on MeeGo...)
ext Alberto Mardegan wrote:
Eero Tamminen wrote:
Hamalainen Kimmo (Nokia-D/Helsi
Hi,
(I resurrected this old thread because there was on meego-dev
mailing list a comment about possibility for RunFast float mode
being enabled by default on MeeGo...)
ext Alberto Mardegan wrote:
Eero Tamminen wrote:
Hamalainen Kimmo (Nokia-D/Helsinki) wrote:
On Wed, 2010-03-10 at 12:57 +0100
Hi,
ext Alberto Mardegan wrote:
Right. Just to complete the picture, here's the same data with -O2:
float (fast mode enabled):
map_path_calculate_distances: 40 ms for 8250 points
map_path_calculate_distances: 2 ms for 430 points
double (fast mode enabled):
Note that fast mode affects only fl
Siarhei Siamashka wrote:
The output (application compiled with -O0):
Using an optimized build (-O2 or -O3) may sometimes change the overall picture
quite dramatically. It makes almost no sense benchmarking -O0 code, because in
this case all the local variables are kept in memory and are read/wr
[float/double/vfp/neon etc.]
There's some information collected at
http://pandorawiki.org/Floating_Point_Optimization
There are also several long threads over at the Pandora forum about
everything discussed in this thread.
-Tor
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maemo-developers mail
On Thu, 2010-03-11 at 00:32 +0200, Siarhei Siamashka wrote:
> On Wednesday 10 March 2010, Laurent GUERBY wrote:
> > GCC comes with some builtins for neon, they're defined in arm_neon.h
> > see below.
>
> This does not sound like a good idea. If the code has to be modified and
> changed into someth
On Wednesday 10 March 2010, Laurent GUERBY wrote:
> On Wed, 2010-03-10 at 21:54 +0200, Siarhei Siamashka wrote:
> > I wonder why the compiler does not use real NEON instructions with
> > -ffast-math option, it should be quite useful even for scalar code.
> >
> > something like:
> >
> > vld1.32 {d0
On Wednesday 10 March 2010, Laurent Desnogues wrote:
> Even if fast-math is known to break some rules, it only
> breaks C rules IIRC. OTOH, NEON FP has no support
> for NaN and other nice things from IEEE754.
And just checked gcc man page to verify this stuff.
-ffast-math
Sets -fno-math-errno
On Wednesday 10 March 2010, Laurent Desnogues wrote:
> On Wed, Mar 10, 2010 at 8:54 PM, Siarhei Siamashka
> wrote:
> [...]
>
> > I wonder why the compiler does not use real NEON instructions with
> > -ffast-math option, it should be quite useful even for scalar code.
> >
> > something like:
> >
>
On Wed, 2010-03-10 at 21:54 +0200, Siarhei Siamashka wrote:
> I wonder why the compiler does not use real NEON instructions with
> -ffast-math
> option, it should be quite useful even for scalar code.
>
> something like:
>
> vld1.32 {d0[0]}, [r0]
> vadd.f32 d0, d0, d0
> vst1.32 {d0[0]}, [r0]
On Wed, Mar 10, 2010 at 8:54 PM, Siarhei Siamashka
wrote:
[...]
> I wonder why the compiler does not use real NEON instructions with -ffast-math
> option, it should be quite useful even for scalar code.
>
> something like:
>
> vld1.32 {d0[0]}, [r0]
> vadd.f32 d0, d0, d0
> vst1.32 {d0[0]}, [r0]
>
On Wednesday 10 March 2010, Laurent Desnogues wrote:
> On Wed, Mar 10, 2010 at 7:29 PM, Alberto Mardegan
> > So, it seems that there's a huge improvements when switching from doubles
> > to floats; although I wonder if it's because of the FPU or just because
> > the amount of data passed around is
On Wednesday 10 March 2010, Alberto Mardegan wrote:
> Alberto Mardegan wrote:
> > Does one have any figure about how the performance of the FPU is,
> > compared to integer operations?
>
> I added some profiling to the code, and I measured the time spent by a
> function which is operating on an arra
On Wed, Mar 10, 2010 at 7:29 PM, Alberto Mardegan
wrote:
> Alberto Mardegan wrote:
>>
>> Does one have any figure about how the performance of the FPU is, compared
>> to integer operations?
>
> I added some profiling to the code, and I measured the time spent by a
> function which is operating on
On Wed, 2010-03-10 at 20:29 +0200, Alberto Mardegan wrote:
> Alberto Mardegan wrote:
> > Does one have any figure about how the performance of the FPU is,
> > compared to integer operations?
>
> I added some profiling to the code, and I measured the time spent by a
> function which is operating
Alberto Mardegan wrote:
Does one have any figure about how the performance of the FPU is,
compared to integer operations?
I added some profiling to the code, and I measured the time spent by a
function which is operating on an array of points (whose coordinates are
integers) and trasforming e
Eero Tamminen wrote:
Is there any performance penalty if this switch is done often?
Why you would switch it off?
Operations on "fast floats" aren't IEEE compatible, but as far as
I've understood, they should differ only for numbers that are very close
to zero, close enough that repeating your
Eero Tamminen wrote:
Hamalainen Kimmo (Nokia-D/Helsinki) wrote:
On Wed, 2010-03-10 at 12:57 +0100, ext Alberto Mardegan wrote:
Kimmo Hämäläinen wrote:
You can also put the CPU to a "fast floats" mode, see hd_fpu_set_mode()
in
http://maemo.gitorious.org/fremantle-hildon-desktop/hildon-desktop/b
Hi,
Hamalainen Kimmo (Nokia-D/Helsinki) wrote:
On Wed, 2010-03-10 at 12:57 +0100, ext Alberto Mardegan wrote:
Kimmo Hämäläinen wrote:
You can also put the CPU to a "fast floats" mode, see hd_fpu_set_mode()
in
http://maemo.gitorious.org/fremantle-hildon-desktop/hildon-desktop/blobs/master/src/m
Hi,
ext Alberto Mardegan wrote:
Kimmo Hämäläinen wrote:
You can also put the CPU to a "fast floats" mode, see hd_fpu_set_mode()
in
http://maemo.gitorious.org/fremantle-hildon-desktop/hildon-desktop/blobs/master/src/main.c
N900 has support for NEON instructions also.
This sounds interesting!
On Wed, 2010-03-10 at 12:57 +0100, ext Alberto Mardegan wrote:
> Kimmo Hämäläinen wrote:
> > You can also put the CPU to a "fast floats" mode, see hd_fpu_set_mode()
> > in
> > http://maemo.gitorious.org/fremantle-hildon-desktop/hildon-desktop/blobs/master/src/main.c
> >
> > N900 has support for NE
Kimmo Hämäläinen wrote:
You can also put the CPU to a "fast floats" mode, see hd_fpu_set_mode()
in
http://maemo.gitorious.org/fremantle-hildon-desktop/hildon-desktop/blobs/master/src/main.c
N900 has support for NEON instructions also.
This sounds interesting!
Is there any performance penalty
On Wed, 2010-03-10 at 10:46 +0100, ext Ove Kaaven wrote:
> Alberto Mardegan skrev:
> > Does anyone know any tricks to optimize certain operations on arrays of
> > data?
>
> The answer to that is, obviously, to use the Cortex-A-series SIMD
> engine, NEON.
>
> Supposedly you may be able to make gcc
Dnia środa, 10 marca 2010 o 11:14:14 Laurent Desnogues napisał(a):
> One has to be careful with that approach: Cortex-A9 SoC won't
> necessarily come with a NEON SIMD unit, as it's optional. So it'd
> be better to also include code that doesn't assume one has a
> NEON unit.
Or if someone will t
On Wed, Mar 10, 2010 at 10:46 AM, Ove Kaaven wrote:
> Alberto Mardegan skrev:
>> Does anyone know any tricks to optimize certain operations on arrays of
>> data?
>
> The answer to that is, obviously, to use the Cortex-A-series SIMD
> engine, NEON.
>
> Supposedly you may be able to make gcc generat
> > in maemo-mapper I have a lot of code involved in doing
> > transformations from latitude/longitude to Mercator
> > coordinates (used in google maps, for example), calculation
> > of distances, etc.
> >
> > I'm trying to use integer arithmetics as much as
> > possible, but som
Alberto Mardegan skrev:
> Does anyone know any tricks to optimize certain operations on arrays of
> data?
The answer to that is, obviously, to use the Cortex-A-series SIMD
engine, NEON.
Supposedly you may be able to make gcc generate NEON instructions with
-mfpu=neon -ffast-math -ftree-vectorize
Hi Alberto!
On Wed, Mar 10, 2010 at 9:55 AM, Alberto Mardegan <
ma...@users.sourceforge.net> wrote:
> Hi all,
> in maemo-mapper I have a lot of code involved in doing transformations
> from latitude/longitude to Mercator coordinates (used in google maps, for
> example), calculation of distances,
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