Differential D13646 Diff 36921 libs/image/vc_extra_math.h

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libs/image/vc_extra_math.h

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		1		/*
		2		* Copyright (c) 2018 Iván Santa María <ghevan@gmail.com>
		3		*
		4		* This program is free software; you can redistribute it and/or modify
		5		* it under the terms of the GNU General Public License as published by
		6		* the Free Software Foundation; either version 2 of the License, or
		7		* (at your option) any later version.
		8		*
		9		* This program is distributed in the hope that it will be useful,
		10		* but WITHOUT ANY WARRANTY; without even the implied warranty of
		11		* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
		12		* GNU General Public License for more details.
		13		*
		14		* You should have received a copy of the GNU General Public License
		15		* along with this program; if not, write to the Free Software
		16		* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
		17		*/
		18
		19		#ifndef VC_ADDITIONAL_MATH_H
		20		#define VC_ADDITIONAL_MATH_H
		21
		22		#include <config-vc.h>
		23
		24		#if defined HAVE_VC
		25
		26		#include <Vc/Vc>
		27		#include <Vc/IO>
		28
		29		class VcExtraMath
		30		{
		31		public:
		32		// vectorized erf function, precision 1e-5
		33		static inline Vc::float_v erf(Vc::float_v x) {
		34		Vc::float_v xa = abs(x);
		35		Vc::float_m precisionLimit(xa >= 9.3f); // wrong result for any number beyond this
		36		xa(precisionLimit) = 0;
		37		Vc::float_v sign(Vc::One);
		38		Vc::float_m invertMask = x < 0.f;
		39		sign(invertMask) = -1.f;
		40
		41		// CONSTANTS
		42		float a1 = 0.254829592;
		43		float a2 = -0.284496736;
		44		float a3 = 1.421413741;
		45		float a4 = -1.453152027;
		46		float a5 = 1.061405429;
		47		float p = 0.3275911;
		48
		49		Vc::float_v t = 1.0f / (1.0f + p * xa);
		50		Vc::float_v y = 1.0f - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * exp(-xa * xa);
		51		y(precisionLimit) = 1.0f;
		52		return sign * y;
		53		}
		54		};
		55		#endif /* defined HAVE_VC */
		56
		57
		58		#endif // VC_ADDITIONAL_MATH_H