Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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5 years ago
//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
//=====================================================================================//
#include "mathlib/ssemath.h"
// NOTE: This has to be the last file included!
#include "tier0/memdbgon.h"
fltx4 Pow_FixedPoint_Exponent_SIMD( const fltx4 & x, int exponent)
{
fltx4 rslt=Four_Ones; // x^0=1.0
int xp=abs(exponent);
if (xp & 3) // fraction present?
{
fltx4 sq_rt=SqrtEstSIMD(x);
if (xp & 1) // .25?
rslt=SqrtEstSIMD(sq_rt); // x^.25
if (xp & 2)
rslt=MulSIMD(rslt,sq_rt);
}
xp>>=2; // strip fraction
fltx4 curpower=x; // curpower iterates through x,x^2,x^4,x^8,x^16...
while(1)
{
if (xp & 1)
rslt=MulSIMD(rslt,curpower);
xp>>=1;
if (xp)
curpower=MulSIMD(curpower,curpower);
else
break;
}
if (exponent<0)
return ReciprocalEstSaturateSIMD(rslt); // pow(x,-b)=1/pow(x,b)
else
return rslt;
}
/*
* (c) Ian Stephenson
*
* ian@dctsystems.co.uk
*
* Fast pow() reference implementation
*/
static float shift23=(1<<23);
static float OOshift23=1.0/(1<<23);
float FastLog2(float i)
{
float LogBodge=0.346607f;
float x;
float y;
x=*(int *)&i;
x*= OOshift23; //1/pow(2,23);
x=x-127;
y=x-floorf(x);
y=(y-y*y)*LogBodge;
return x+y;
}
float FastPow2(float i)
{
float PowBodge=0.33971f;
float x;
float y=i-floorf(i);
y=(y-y*y)*PowBodge;
x=i+127-y;
x*= shift23; //pow(2,23);
*(int*)&x=(int)x;
return x;
}
float FastPow(float a, float b)
{
if (a <= OOshift23)
{
return 0.0f;
}
return FastPow2(b*FastLog2(a));
}
float FastPow10( float i )
{
return FastPow2( i * 3.321928f );
}