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/* -------------------------------------------------------------- */
/* (C)Copyright 2006,2007, */
/* International Business Machines Corporation */
/* All Rights Reserved. */
/* */
/* Redistribution and use in source and binary forms, with or */
/* without modification, are permitted provided that the */
/* following conditions are met: */
/* */
/* - Redistributions of source code must retain the above copyright*/
/* notice, this list of conditions and the following disclaimer. */
/* */
/* - Redistributions in binary form must reproduce the above */
/* copyright notice, this list of conditions and the following */
/* disclaimer in the documentation and/or other materials */
/* provided with the distribution. */
/* */
/* - Neither the name of IBM Corporation nor the names of its */
/* contributors may be used to endorse or promote products */
/* derived from this software without specific prior written */
/* permission. */
/* Redistributions of source code must retain the above copyright */
/* notice, this list of conditions and the following disclaimer. */
/* */
/* Redistributions in binary form must reproduce the above */
/* copyright notice, this list of conditions and the following */
/* disclaimer in the documentation and/or other materials */
/* provided with the distribution. */
/* */
/* Neither the name of IBM Corporation nor the names of its */
/* contributors may be used to endorse or promote products */
/* derived from this software without specific prior written */
/* permission. */
/* */
/* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */
/* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */
/* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */
/* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */
/* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */
/* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */
/* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */
/* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */
/* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */
/* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */
/* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */
/* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */
/* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
/* -------------------------------------------------------------- */
/* PROLOG END TAG zYx */
#ifdef __SPU__
#ifndef _ERFF4_H_
#define _ERFF4_H_ 1
#include <spu_intrinsics.h>
#include "expf4.h"
#include "recipf4.h"
#include "divf4.h"
#include "erf_utils.h"
/*
* FUNCTION
* vector float _erff4(vector float x)
*
* DESCRIPTION
* The erff4 function computes the error function of each element of x.
*
* C99 Special Cases:
* - erf(+0) returns +0
* - erf(-0) returns -0
* - erf(+infinite) returns +1
* - erf(-infinite) returns -1
*
*/
static __inline vector float _erff4(vector float x)
{
vector float onehalff = spu_splats(0.5f);
vector float zerof = spu_splats(0.0f);
vector float onef = spu_splats(1.0f);
vector float sign_mask = spu_splats(-0.0f);
/* This is where we switch from Taylor Series to Continued Fraction approximation */
vec_float4 approx_point = spu_splats(0.89f);
vec_float4 xabs, xsqu, xsign;
vec_uint4 isinf;
vec_float4 tresult, presult, result;
xsign = spu_and(x, sign_mask);
/* Force Denorms to 0 */
x = spu_add(x, zerof);
xabs = spu_andc(x, sign_mask);
xsqu = spu_mul(x, x);
/*
* Taylor Series Expansion near Zero
*/
TAYLOR_ERFF4(xabs, xsqu, tresult);
/*
* Continued Fraction Approximation of Erfc().
* erf = 1 - erfc
*/
CONTFRAC_ERFCF4(xabs, xsqu, presult);
presult = spu_sub(onef, presult);
/*
* Select the appropriate approximation.
*/
result = spu_sel(tresult, presult, spu_cmpgt(xabs, approx_point));
/*
* Special cases/errors.
*/
/* x = +/- infinite, return +/-1 */
isinf = spu_cmpeq((vec_uint4)xabs, 0x7F800000);
result = spu_sel(result, onef, isinf);
/*
* Preserve sign in result, since erf(-x) = -erf(x)
*/
result = spu_or(result, xsign);
return result;
}
#endif /* _ERFF4_H_ */
#endif /* __SPU__ */
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