Hello!
That was a long time ago and there were no objections so I made a bug
for the further discussions and patches:
https://bugs.webkit.org/show_bug.cgi?id=98913
Regards,
Gabor
What CPU executes single precision floating point values at the same speed as
double precision?
Here's a benchmark from NASA giving a comparison of single vs. double precision
performance for one of their simulations.
https://modelingguru.nasa.gov/docs/DOC-1664.
Single precision maps better to GPU backends, and CPU's SIMD computations than
double. Unless there's something in the spec requiring double precision it
makes sense to move away from double precision throughout WebKit.
It's fairly trivial to make SIMD types that can have CPU architecture specific
implementations. As an example of how to do this in the wild there's the Sony
vectormath library that's present in the Bullet Physics Library.
http://bullet.svn.sourceforge.net/viewvc/bullet/trunk/Extras/vectormathlibrary/include/vectormath/.
As Kui noted the TransformationMatrix is a hotspot that could be helped by
SIMD. Making the solution generic enough to target multiple architectures using
SIMD should help the performance on all the platforms.
Don
-----Original Message-----
From: webkit-dev-boun...@lists.webkit.org
[mailto:webkit-dev-boun...@lists.webkit.org] On Behalf Of Simon Fraser
Sent: Monday, May 21, 2012 10:35 AM
To: Zoltan Herczeg
Cc: webkit-dev@lists.webkit.org
Subject: Re: [webkit-dev] Transformations precision: double -> float
TransformationMatrix started out as floats, then got changed to doubles in
<http://trac.webkit.org/changeset/40761>
This was done because on most hardware there is no penalty for using doubles
over floats, and provided a better match with our system APIs that used doubles.
I'd prefer to take a forward-looking stance here, and assume that in time
hardware will catch up.
Simon
On May 21, 2012, at 4:04 AM, Zoltan Herczeg wrote:
Hi,
is there any reason why the transformations in WebKit use doubles? We
could optimize some functions further with ARM SIMD if they would be
floats. Is there any objection to make them float if the change would
have no other side effects except some rounding because of the lower precision?
Regards,
Zoltan
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