[cairo] [Pixman] FPU requirement in SoC based devices

Siarhei Siamashka siarhei.siamashka at gmail.com
Thu Aug 26 09:00:42 PDT 2010

On Wednesday 25 August 2010 04:36:27 M.R. wrote:
> Floating point hardware is a reasonable requirement on a dedicated
> SoC device that models some application-domain process that deals
> with physical measurements and is thus by its nature best representable
> with real numbers. But if the cost of hardware is critical and press
> run is high, floating point should never be made necessary just to
> reduce the display-driving software development cost,

I don't quite like the wording "reduction of development cost". It's just that
hardware platforms without a (fast) FPU unit are adding more diversity.
Software developers now either have to "run after two hares", or make a choice
about what class of hardware is the primary target to focus on. The other types 
of hardware will lose some performance as a result, unless somebody puts an 
effort into solving this problem by maintaining alternative optimized code 
paths or introducing some clever improvements which work best for everyone.

SoC devices without FPU still can run floating point code perfectly fine. They
are just slow because floating point calculations are performed via software 
emulation library.

> especially if the only purpose of the display is man/machine interface (i.e.,
> the "control panel" display), not the visualization of some application-
> -domain process.

What are the typical cairo/pixman usage patterns on such hardware? Are 
coordinate transforms and matrix operations really important and performance 
critical there? I suppose that some benchmarks or cairo traces would be welcome

Let me remind that the original problem is that using 16.16 fixed point format
for coordinates is the source of some issues:

It has to be solved somehow. And anyone can participate proposing some good 
solution for it.

Best regards,
Siarhei Siamashka
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