On Saturday, 20 de August de 2011 08:16:45 [email protected] wrote: > > Unfortunately, the argument to the contrary is that double-precision > > floating point on the ARM Cortex-A8 is still much worse than > > single-precision -- it's even worse than on ARM11. Only on the A9 is the > > performance acceptable. > I would think this is fine though, double will be used so seldom that in > practice it won't impact performance much. > > Both QML Scene Graph and Qt3D use primarily floats for the vertex data and > other parameters, for instance.
Which is good, that's where the math is concentrated. Using doubles for
parameter passing isn't a big deal, however, provided a "hard float" approach
is used (passing parameters in registers). Loading and storing, converting to
single precision, etc., shouldn't take too much time, not much worse than float
itself.
The difficulty lies in writing single-precision code, as C and C++ have an
automatic promotion to double. More difficult than that is to write code that
operates on shorts, since promotion to int happens even more easily.
--
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
Software Architect - Intel Open Source Technology Center
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