[WP-34S] DEG and RAD - diffs

[Claudio L.]

(06-06-2014 10:27 PM)Paul Dale Wrote:  

(06-06-2014 04:24 PM)Claudio L. Wrote:  You can indeed achieve convergence by repeating rotations with the same angle. But it's bad for speed!

If you want speed on a modern CPU, don't use CORDIC. Multiplications and additions are similar speed on the 34S -- software floating point is slow but hardware integer operations help a lot.

If I were chasing speed, I'd likely use polynomial or rational approximations. Probably piecewise ones. This will result in larger code sizes. The Intel decimal library recently discussed here did exactly this. Lots of approximations over small intervals meant lots of tables of coefficients but the code is fast and accurate.

Of course, there are other options available. Elementary Functions by Jean-Michel Muller is a good book giving details of many method.


- Pauli

More than speed of execution, I was looking at speed of coding. I got all transcendental functions with the same loop, and only a few variations around the same idea over the course of a few weeks. I got a lot of ground to cover, can't spend a whole year doing just trig.

Once newRPL is finished, then I might attempt to do a piecewise-optimized version.

Claudio