[Kstars-devel] Precision in KStars

[Aleksey Khudyakov]

On 25 June 2013 08:56, Daniel Baboiu <daniel.baboiu at shaw.ca> wrote:
> The level of precision for single precision, if we are talking only
> computations related to rendering, and if there are only a handful of
> steps, would be sufficient. The precision is 1e-8, for a full circle,
> leads to an error of about 0.01-0.02 arcsec.
>
It's 1e-7 actually. So quantization will be at level of 0.1 arcsec. It's
not prohibitive but dangerously close. Would we lose precision it could
lead to problems. Probably calculation of projections should will
be OK. Everywhere elese we should user double just to be safe.
It would be difficult enough to detect precision related bug.

Is it possible to select between float/double at compile time by using typedef
and maybe bunch of #defines? This way it's possible to use float for speed
and fall back to double it won't work out.



> On the other hand, if the original data only provides say 7 digit
> precision, the use of SP is perfectly justified.
>
It's more about having spare digit to lose.



> *: In the event that we don't have hardware OpenCL support, we can use a
> software implementation such as pocl (http://pocl.sourceforge.net/). To be
> very clear, even though this architecture is aimed to run entirely on the GPU,
> this is not required.

Regarding OpenCL availability. Will it work with open-source drivers? If answer
is no then CPU performance is priority. A lot of users won't be able
to use their
GPU.