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**To**:**tech-kern%netbsd.org@localhost****Subject**:**Re: atan2 and sqrt --> in driver****From**:**"Robert Fritzsche" <robert.fritzsche%googlemail.com@localhost>**- Date: Tue, 9 Dec 2008 23:42:59 +0100

ok will try approaches for sqrt and atan2. txl 2008/12/9 Joerg Sonnenberger <joerg%britannica.bec.de@localhost>: > On Tue, Dec 09, 2008 at 02:42:45PM -0500, der Mouse wrote: >> >> The driver is for the wii-remote, so get 1 byte for x-, y- and >> >> z-axis. Based on this values I will calculate the >> >> pitch = atan2(y, sqrt(x^2+z^2)) and yaw = atan2(z, sqrt(x^2+y^2)) >> >> Why do these have to be done in the driver, rather than userland? > > Well, I think our wsmouse interface allows only absolute coordinates > right now. > >> > Alternatively, just provide a data table, indexed by 0..255 x 0..255, >> > with the second operand shifted and the sqrt computed in integer >> > math. Search wikipedia for easy algorithms to compute isqrt. >> >> Since sqrt isn't being used in full generality, but just for hypot(), >> you could use a lookup table for that too. Even with cache miss >> effects I suspect it may be faster than integer square root code >> (though I'd want to benchmark before saying anything definite). > > I wasn't thinking much about speed, just size. Computing integer square > root is simple, atan2 likely is more involved. > > Joerg >

**References**:**atan2 and sqrt --> in driver***From:*Robert Fritzsche

**Re: atan2 and sqrt --> in driver***From:*Ignatios Souvatzis

**Re: atan2 and sqrt --> in driver***From:*Robert Fritzsche

**Re: atan2 and sqrt --> in driver***From:*Joerg Sonnenberger

**Re: atan2 and sqrt --> in driver***From:*der Mouse

**Re: atan2 and sqrt --> in driver***From:*Joerg Sonnenberger

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