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@pmineiro
pmineiro committed Jul 7, 2011
1 parent a75125b commit 1c422cb
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Showing 2 changed files with 28 additions and 40 deletions.
34 changes: 14 additions & 20 deletions fastapprox/src/fasterf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,19 +55,17 @@ static inline float
fasterfc (float x)
{
static const float k = 3.3509633149424609f;
static const float a = 0.0846486355377475f;
static const float b = 1.6732800045663587f;
static const float c = 5.604430819154318f;
static const float a = 0.07219054755431126f;
static const float b = 15.418191568719577f;
static const float c = 5.609846028328545f;

float bx = b * x;
union { float f; uint32_t i; } vc = { c * x };
float bxsq = bx * bx;
float bxquad = bxsq * bxsq;
float bxfive = bxquad * bx;
float xsq = x * x;
float xquad = xsq * xsq;

vc.i |= 0x80000000;

return 2.0f / (1.0f + fastpow2 (k * x)) - a * (bxfive - x) * fasterpow2 (vc.f);
return 2.0f / (1.0f + fastpow2 (k * x)) - a * x * (b * xquad - 1.0f) * fasterpow2 (vc.f);
}

static inline float
Expand Down Expand Up @@ -104,10 +102,9 @@ fastinverseerf (float x)
static const float d = 0.8059775923760193f;

float xsq = x * x;
float xcube = xsq * x;

return invk * fastlog2 ((1.0f + x) / (1.0f - x))
+ (a * x - b * xcube) / (c - d * xsq);
+ x * (a - b * xsq) / (c - d * xsq);
}

static inline float
Expand All @@ -124,19 +121,17 @@ static inline v4sf
vfasterfc (v4sf x)
{
static const v4sf k = v4sfl (3.3509633149424609f);
static const v4sf a = v4sfl (0.0846486355377475f);
static const v4sf b = v4sfl (1.6732800045663587f);
static const v4sf c = v4sfl (5.604430819154318f);
static const v4sf a = v4sfl (0.07219054755431126f);
static const v4sf b = v4sfl (15.418191568719577f);
static const v4sf c = v4sfl (5.609846028328545f);

union { v4sf f; v4si i; } vc = { c * x };
vc.i |= v4sil (0x80000000);

v4sf bx = b * x;
v4sf bxsq = bx * bx;
v4sf bxquad = bxsq * bxsq;
v4sf bxfive = bxquad * bx;
v4sf xsq = x * x;
v4sf xquad = xsq * xsq;

return v4sfl (2.0f) / (v4sfl (1.0f) + vfastpow2 (k * x)) - a * (bxfive - x) * vfasterpow2 (vc.f);
return v4sfl (2.0f) / (v4sfl (1.0f) + vfastpow2 (k * x)) - a * x * (b * xquad - v4sfl (1.0f)) * vfasterpow2 (vc.f);
}

static inline v4sf
Expand Down Expand Up @@ -169,10 +164,9 @@ vfastinverseerf (v4sf x)
static const v4sf d = v4sfl (0.8059775923760193f);

v4sf xsq = x * x;
v4sf xcube = xsq * x;

return invk * vfastlog2 ((v4sfl (1.0f) + x) / (v4sfl (1.0f) - x))
+ (a * x - b * xcube) / (c - d * xsq);
+ x * (a - b * xsq) / (c - d * xsq);
}

static inline v4sf
Expand Down
34 changes: 14 additions & 20 deletions fastapprox/src/fastonebigheader.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -397,19 +397,17 @@ static inline float
fasterfc (float x)
{
static const float k = 3.3509633149424609f;
static const float a = 0.0846486355377475f;
static const float b = 1.6732800045663587f;
static const float c = 5.604430819154318f;
static const float a = 0.07219054755431126f;
static const float b = 15.418191568719577f;
static const float c = 5.609846028328545f;

float bx = b * x;
union { float f; uint32_t i; } vc = { c * x };
float bxsq = bx * bx;
float bxquad = bxsq * bxsq;
float bxfive = bxquad * bx;
float xsq = x * x;
float xquad = xsq * xsq;

vc.i |= 0x80000000;

return 2.0f / (1.0f + fastpow2 (k * x)) - a * (bxfive - x) * fasterpow2 (vc.f);
return 2.0f / (1.0f + fastpow2 (k * x)) - a * x * (b * xquad - 1.0f) * fasterpow2 (vc.f);
}

static inline float
Expand Down Expand Up @@ -446,10 +444,9 @@ fastinverseerf (float x)
static const float d = 0.8059775923760193f;

float xsq = x * x;
float xcube = xsq * x;

return invk * fastlog2 ((1.0f + x) / (1.0f - x))
+ (a * x - b * xcube) / (c - d * xsq);
+ x * (a - b * xsq) / (c - d * xsq);
}

static inline float
Expand All @@ -466,19 +463,17 @@ static inline v4sf
vfasterfc (v4sf x)
{
static const v4sf k = v4sfl (3.3509633149424609f);
static const v4sf a = v4sfl (0.0846486355377475f);
static const v4sf b = v4sfl (1.6732800045663587f);
static const v4sf c = v4sfl (5.604430819154318f);
static const v4sf a = v4sfl (0.07219054755431126f);
static const v4sf b = v4sfl (15.418191568719577f);
static const v4sf c = v4sfl (5.609846028328545f);

union { v4sf f; v4si i; } vc = { c * x };
vc.i |= v4sil (0x80000000);

v4sf bx = b * x;
v4sf bxsq = bx * bx;
v4sf bxquad = bxsq * bxsq;
v4sf bxfive = bxquad * bx;
v4sf xsq = x * x;
v4sf xquad = xsq * xsq;

return v4sfl (2.0f) / (v4sfl (1.0f) + vfastpow2 (k * x)) - a * (bxfive - x) * vfasterpow2 (vc.f);
return v4sfl (2.0f) / (v4sfl (1.0f) + vfastpow2 (k * x)) - a * x * (b * xquad - v4sfl (1.0f)) * vfasterpow2 (vc.f);
}

static inline v4sf
Expand Down Expand Up @@ -511,10 +506,9 @@ vfastinverseerf (v4sf x)
static const v4sf d = v4sfl (0.8059775923760193f);

v4sf xsq = x * x;
v4sf xcube = xsq * x;

return invk * vfastlog2 ((v4sfl (1.0f) + x) / (v4sfl (1.0f) - x))
+ (a * x - b * xcube) / (c - d * xsq);
+ x * (a - b * xsq) / (c - d * xsq);
}

static inline v4sf
Expand Down

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