TF2-Source-Code/tf2_src/mathlib/randsse.cpp at master · sr2echa/TF2-Source-Code · GitHub

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// Purpose: generates 4 randum numbers in the range 0..1 quickly, using SIMD

//=====================================================================================//

#include <math.h>

#include <float.h> // Needed for FLT_EPSILON

#include "basetypes.h"

#include <memory.h>

#include "tier0/dbg.h"

#include "mathlib/mathlib.h"

#include "mathlib/vector.h"

#include "mathlib/ssemath.h"

// memdbgon must be the last include file in a .cpp file!!!

#include "tier0/memdbgon.h"

// see knuth volume 3 for insight.

class SIMDRandStreamContext

{

fltx4 m_RandY[55];

fltx4 *m_pRand_J, *m_pRand_K;

public:

void Seed( uint32 seed )

{

m_pRand_J=m_RandY+23; m_pRand_K=m_RandY+54;

for(int i=0;i<55;i++)

{

for(int j=0;j<4;j++)

{

SubFloat( m_RandY[i], j) = (seed>>16)/65536.0;

seed=(seed+1)*3141592621u;

}

inline fltx4 RandSIMD( void )

{

// ret= rand[k]+rand[j]

fltx4 retval=AddSIMD( *m_pRand_K, *m_pRand_J );

// if ( ret>=1.0) ret-=1.0

fltx4 overflow_mask=CmpGeSIMD( retval, Four_Ones );

retval=SubSIMD( retval, AndSIMD( Four_Ones, overflow_mask ) );

*m_pRand_K = retval;

// update pointers w/ wrap-around

if ( --m_pRand_J < m_RandY )

m_pRand_J=m_RandY+54;

if ( --m_pRand_K < m_RandY )

m_pRand_K=m_RandY+54;

return retval;

}

};

#define MAX_SIMULTANEOUS_RANDOM_STREAMS 32

static SIMDRandStreamContext s_SIMDRandContexts[MAX_SIMULTANEOUS_RANDOM_STREAMS];

static volatile int s_nRandContextsInUse[MAX_SIMULTANEOUS_RANDOM_STREAMS];

void SeedRandSIMD(uint32 seed)

{

for( int i = 0; i<MAX_SIMULTANEOUS_RANDOM_STREAMS; i++)

s_SIMDRandContexts[i].Seed( seed+i );

}

fltx4 RandSIMD( int nContextIndex )

{

return s_SIMDRandContexts[nContextIndex].RandSIMD();

}

int GetSIMDRandContext( void )

{

for(;;)

{

for(int i=0; i < NELEMS( s_SIMDRandContexts ); i++)

{

if ( ! s_nRandContextsInUse[i] ) // available?

{

// try to take it!

if ( ThreadInterlockedAssignIf( &( s_nRandContextsInUse[i]), 1, 0 ) )

{

return i; // done!

}

Assert(0); // why don't we have enough buffers?

ThreadSleep();

}

void ReleaseSIMDRandContext( int nContext )

{

s_nRandContextsInUse[ nContext ] = 0;

}

fltx4 RandSIMD( void )

{

return s_SIMDRandContexts[0].RandSIMD();

}

TF2-Source-Code/tf2_src/mathlib/randsse.cpp at master · sr2echa/TF2-Source-Code · GitHub

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