97 lines
1.7 KiB
C++
97 lines
1.7 KiB
C++
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//========= Copyright Valve Corporation, All rights reserved. ============//
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//
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// Purpose:
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//
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//=====================================================================================//
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#include "mathlib/ssemath.h"
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// NOTE: This has to be the last file included!
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#include "tier0/memdbgon.h"
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fltx4 Pow_FixedPoint_Exponent_SIMD( const fltx4 & x, int exponent)
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{
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fltx4 rslt=Four_Ones; // x^0=1.0
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int xp=abs(exponent);
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if (xp & 3) // fraction present?
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{
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fltx4 sq_rt=SqrtEstSIMD(x);
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if (xp & 1) // .25?
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rslt=SqrtEstSIMD(sq_rt); // x^.25
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if (xp & 2)
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rslt=MulSIMD(rslt,sq_rt);
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}
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xp>>=2; // strip fraction
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fltx4 curpower=x; // curpower iterates through x,x^2,x^4,x^8,x^16...
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while(1)
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{
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if (xp & 1)
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rslt=MulSIMD(rslt,curpower);
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xp>>=1;
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if (xp)
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curpower=MulSIMD(curpower,curpower);
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else
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break;
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}
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if (exponent<0)
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return ReciprocalEstSaturateSIMD(rslt); // pow(x,-b)=1/pow(x,b)
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else
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return rslt;
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}
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/*
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* (c) Ian Stephenson
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*
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* ian@dctsystems.co.uk
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*
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* Fast pow() reference implementation
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*/
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static float shift23=(1<<23);
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static float OOshift23=1.0/(1<<23);
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float FastLog2(float i)
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{
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float LogBodge=0.346607f;
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float x;
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float y;
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x=*(int *)&i;
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x*= OOshift23; //1/pow(2,23);
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x=x-127;
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y=x-floorf(x);
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y=(y-y*y)*LogBodge;
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return x+y;
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}
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float FastPow2(float i)
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{
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float PowBodge=0.33971f;
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float x;
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float y=i-floorf(i);
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y=(y-y*y)*PowBodge;
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x=i+127-y;
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x*= shift23; //pow(2,23);
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*(int*)&x=(int)x;
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return x;
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}
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float FastPow(float a, float b)
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{
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if (a <= OOshift23)
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{
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return 0.0f;
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}
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return FastPow2(b*FastLog2(a));
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}
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float FastPow10( float i )
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{
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return FastPow2( i * 3.321928f );
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}
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