sin()/cos()/tan() for kernel code? '_ 'a
Alexander Leidinger
Alexander at Leidinger.net
Mon Feb 12 09:39:33 UTC 2007
Quoting Stephen Montgomery-Smith <stephen at math.missouri.edu> (from
Sun, 11 Feb 2007 12:00:12 -0600 (CST)):
>
>
> On Sun, 11 Feb 2007, Stephen Montgomery-Smith wrote:
>
>>
>>
>> On Sun, 11 Feb 2007, Daniel Eischen wrote:
>>> Can't you do this in userland? Teach moused?
>>
>> Since you will only need sin and cos evaluated to the nearest
>> degree, if that, I suggest a simple look up table. There is also
>> something called the CORDIC method, I think, but I suspect that the
>> look up table will be so much easier to program, and negligable
>> extra space overhead.
>>
>> Stephen
>
> And if you do need more accuracy than the nearest degree, the formulae
>
> sin(x+h) = sin(x) + h cos(x);
> cos(x+h) = cos(x) - h sin(x)
>
> for small h (say |h| less than half a degree) should provide way more
> accuracy than you should need.
There's work underway which moves the hard work of the mouse drivers
from the kernel to moused. The kernel just has a simple hardware
interface there, and the real interpretion of all the stuff from the
mouse happens in the userland.
See http://www.semicomplete.com/projects/newpsm/ for more.
So maybe it would be better to implement this in moused right from the
beginning...
Bye,
Alexander.
--
Love is never asking why?
http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137
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