Efficient way to implement trigonometry functions?

alexpabouct9 · ‎2013-02-02

Posted on February 02, 2013 at 19:28

Hello,

I'm working on the STM32F4, and in my application i need to use atan2 and exp a very large number of times.

In my initial implementation i used the stlib for atan2 and exp. Unfortunately, in the current state my algorithm is too slow to run at the required frequency.

Does anyone have a reference to how these functions are implemented (I'm using GCC 4.7).

Also, does anyone know of a more efficient method to implement these functions? (Taylor series, etc)

Thanks

Alex

#stm32f4-atan2-exp

ken239955 · ‎2013-02-02

Posted on February 02, 2013 at 21:17

The fastest way is to use a lookup table.

Tesla DeLorean · ‎2013-02-02

Posted on February 02, 2013 at 23:27

To stand some chance of using the FPU you'd need to use the float (32-bit) version

float atan2f (float y, float x)

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alexpabouct9 · ‎2013-02-02

Posted on February 03, 2013 at 00:22

Thanks a ton.

It dropped from ~4.7k cycles to 400 :)

Cheers