wrTrig.c

#include "wrTrig.h"

// based on padé expansion
// accepts input values -3 to +3, outside this range needs to be clamped to +/-1
float tanh_fast(float in)
{
	float sq, out;

	if(in <= -3) { // clamp negative values
		out = -1;
	} else if(in >= 3) { // clamp positive values
		out = 1;
	} else {
		sq = in * in; // input squared
		out = in * (27 + sq) / (27 + 9 * sq);
	}

	return out;
}

float* tanh_fast_v( float* buffer
                  , int    b_size
                  ){
	float* in  = buffer;
	float* out = buffer;

	for( int i=0; i<b_size; i++ ){
		if( *in <= -3.0 ){
			*out++ = -1.0;
		} else if( *in >= 3.0 ){
			*out++ = 1.0;
		} else {
			float squared = *in * *in;
			*out++ = *in * (27.0 + squared) / (27.0 + 9.0 * squared);
		}
		in++;
	}
    return buffer;
}