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RedLib and Trigonometric

Question asked by RICHARD PAYNE on Aug 8, 2016
Latest reply on Aug 9, 2016 by LPCX presso support


I getting a bit of confusion on RedLib, partial support on C99 where it provide Trigonometric (sin, cos, tan, tan2 and so on) for both float and double.


I'm using RedLib for LPC1549 project (Cortex M3) which has no FPU. I'm understood that float is 32 bit and double is 64 bits but limited precision of result to 8 digit for float and 14-15 digit for double.


(1) What is performance difference between float and double (compared to Cortex M4 which has FPU) doing sin, cos and tan function. Alternatively, how many clock cycle to complete this process. Is there link for this?

(2) is RedLib a version 2 (I believe it is but not clear on LPCExpresso, it just say RedLib(Auto).

(3) How to minimise common math error when using Trigonometric function. Is there link for this?

(4) How the RedLib perform process on sin, cos, tan, tan2 and sinf, cosf, tanf, do they use look up table or use maths.

(5) Are they fully IEEE754 complaint (in context of results, nothing to do with hardware FPU) or not?


Much thanks and appericate your contribution for this calification.