Exponential Function

Functions
q31_t	csky_dsp_lib_pow_int32 (q31_t arg_in_x, q15_t arg_exp_in_x, q31_t arg_in_y, q15_t arg_exp_in_y, q31_t *arg_exp_out)
	Fast approximation to the exponential function for float64_t-point data. More...

Description

This group includes only one function, which is any value based Exponentional function. The common methods to compute the functions are ploynomial approximation and table loop-up. And, it is a double floating similarly version, whose exponention part and mantissa part are seperated.

Function Documentation

q31_t csky_dsp_lib_pow_int32	(	q31_t	arg_in_x,
		q15_t	arg_exp_in_x,
		q31_t	arg_in_y,
		q15_t	arg_exp_in_y,
		q31_t *	arg_exp_out
	)

Parameters

[in]	arg_in_x	the mantissa of the base of pow.
[in]	arg_exp_in_x	the exponention of the base of pow.
[in]	arg_in_y	the mantissa of the exponention of pow.
[in]	arg_exp_in_y	the exponention of the exponention of pow.
[out]	arg_exp_out	the exponention of the exponention of result.

Returns

the mantissa of the result.

The implementation is based on the transform x^y = e^(y*log(x)).

The steps used are:

1. First, calculation of the nearest value of log(x) with series expansion or table look up depending on the range of x.
2. Then, compute of the nearest value of e^(y*log(x)) with the function e^(x+xx), in which, defferent methods are used based on the range of x.
3. Finally, some special cases are processed.