/* -------------------------------------------------------------- */
/* (C)Copyright 2007,2008, */
/* 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. */
/* 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 _ERFD2_H_
#define _ERFD2_H_ 1
#include <spu_intrinsics.h>
#include "expd2.h"
#include "recipd2.h"
#include "divd2.h"
#include "erf_utils.h"
/*
* FUNCTION
* vector double _erfd2(vector double x)
*
* DESCRIPTION
* The erfd2 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
* Other Cases:
* - erf(Nan) returns Nan
*/
static __inline vector double _erfd2(vector double x)
{
vec_uchar16 dup_even = ((vec_uchar16) { 0,1,2,3, 0,1,2,3, 8, 9,10,11, 8, 9,10,11 });
vec_double2 onehalfd = spu_splats(0.5);
vec_double2 oned = spu_splats(1.0);
vec_double2 sign_mask = spu_splats(-0.0);
/* This is where we switch from Taylor Series to Continued Fraction approximation */
vec_float4 approx_point = spu_splats(1.77f);
vec_double2 xabs, xsqu, xsign;
vec_double2 tresult, presult, result;
xsign = spu_and(x, sign_mask);
xabs = spu_andc(x, sign_mask);
xsqu = spu_mul(x, x);
* Taylor Series Expansion near Zero
TAYLOR_ERF(xabs, xsqu, tresult);
* Continued Fraction Approximation of Erfc().
* erf = 1 - erfc
CONTFRAC_ERFC(xabs, xsqu, presult);
presult = spu_sub(oned, presult);
* Select the appropriate approximation.
vec_float4 xf = spu_roundtf(xabs);
xf = spu_shuffle(xf, xf, dup_even);
result = spu_sel(tresult, presult, (vec_ullong2)spu_cmpgt(xf, approx_point));
* Special cases/errors.
/* x = +/- infinite, return +/-1 */
/* x = nan, return x */
result = spu_sel(result, oned, spu_testsv(x, SPU_SV_NEG_INFINITY | SPU_SV_POS_INFINITY));
result = spu_sel(result, x, spu_testsv(x, SPU_SV_NEG_DENORM | SPU_SV_POS_DENORM));
* Preserve sign in result, since erf(-x) = -erf(x)
result = spu_or(result, xsign);
return result;
}
#endif /* _ERFD2_H_ */
#endif /* __SPU__ */
