Method recip_est1

engine/dlib/src/basis/encoder/cppspmd_math.h:341–354

positive values only

// positive values only
CPPSPMD_FORCE_INLINE vfloat spmd_kernel::recip_est1(const vfloat& q)
{
	//const int mag = 0x7EF312AC; // 2 NR iters, 3 is  0x7EEEEBB3
	const int mag = 0x7EF311C3;
	const float fMinThresh = .0000125f;

	vfloat l = spmd_ternaryf(q >= fMinThresh, q, cast_vint_to_vfloat(vint(mag)));

	vint x_l = vint(mag) - cast_vfloat_to_vint(l);
	
	vfloat rcp_l = cast_vint_to_vfloat(x_l);
	
	return rcp_l * vfnma(rcp_l, q, 2.0f);
}

CPPSPMD_FORCE_INLINE vfloat spmd_kernel::recip_est1_pn(const vfloat& t)
{