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/* PROLOG END TAG zYx                                              */

#ifdef __SPU__

#ifndef _ERFCD2_H_

#define _ERFCD2_H_      1

#include <spu_intrinsics.h>

#include "expd2.h"

#include "recipd2.h"

#include "divd2.h"

#include "erf_utils.h"

/*

 * FUNCTION

 *  vector double _erfcd2(vector double x)

 *

 * DESCRIPTION

 *  The erfcd2 function computes the complement error function of each element of x.

 *

 *  Accuracy Note: We would benefit from a rational approximation in the domain

 *  1.2 < x < 2.0 and also around x = 2.5.

 *

 *  C99 Special Cases:

 *  - erfc(+0) returns +1

 *  - erfc(-0) returns +1

 *  - erfc(+infinite) returns +0

 *  - erfc(-infinite) returns +2

 *

 *  Other Cases:

 *  - erfc(Nan) returns Nan

 *

 */

static __inline vector double _erfcd2(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 zerod     = spu_splats(0.0);

  vec_double2 oned      = spu_splats(1.0);

  vec_double2 twod      = spu_splats(2.0);

  vec_double2 sign_mask = spu_splats(-0.0);

  /* This is where we switch from near zero approx. */

  vec_float4 approx_point = spu_splats(1.71f);

  vec_double2 xabs, xsqu, xsign;

  vec_uint4 isneg;

  vec_double2 tresult, presult, result;

  xsign = spu_and(x, sign_mask);

  xabs = spu_andc(x, sign_mask);

  xsqu = spu_mul(x, x);

  /*

   * Use Taylor Series for x near 0

   * Preserve sign of x in result, since erf(-x) = -erf(x)

   * This approximation is for erf, so adjust for erfc.

   */

  TAYLOR_ERF(xabs, xsqu, tresult);

  tresult = spu_or(tresult, xsign);

  tresult = spu_sub(oned, tresult);

  /*

   * Now, use the Continued Fractions approximation away

   * from 0. If x < 0, use erfc(-x) = 2 - erfc(x)

   */

  CONTFRAC_ERFC(xabs, xsqu, presult);

  isneg = (vec_uint4)spu_shuffle(x, x, dup_even);

  isneg = spu_rlmaska(isneg, -32);

  presult = spu_sel(presult, spu_sub(twod, presult), (vec_ullong2)isneg);

  /*

   * 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

   */

  result = spu_sel(result,  twod, spu_testsv(x, SPU_SV_NEG_INFINITY));

  result = spu_sel(result, zerod, spu_testsv(x, SPU_SV_POS_INFINITY));

  result = spu_sel(result,     x, spu_testsv(x, SPU_SV_NEG_DENORM | SPU_SV_POS_DENORM));

  return result;

}

#endif /* _ERFCD2_H_ */

#endif /* __SPU__ */