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110 lines
2.3 KiB
C++
110 lines
2.3 KiB
C++
//========= Copyright Valve Corporation, All rights reserved. ============//
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//
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// Purpose: generates 4 randum numbers in the range 0..1 quickly, using SIMD
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//
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//=====================================================================================//
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#include <math.h>
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#include <float.h> // Needed for FLT_EPSILON
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#include "basetypes.h"
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#include <memory.h>
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#include "tier0/dbg.h"
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#include "mathlib/mathlib.h"
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#include "mathlib/vector.h"
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#include "mathlib/ssemath.h"
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// memdbgon must be the last include file in a .cpp file!!!
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#include "tier0/memdbgon.h"
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// see knuth volume 3 for insight.
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class SIMDRandStreamContext
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{
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fltx4 m_RandY[55];
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fltx4 *m_pRand_J, *m_pRand_K;
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public:
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void Seed( uint32 seed )
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{
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m_pRand_J=m_RandY+23; m_pRand_K=m_RandY+54;
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for(int i=0;i<55;i++)
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{
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for(int j=0;j<4;j++)
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{
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SubFloat( m_RandY[i], j) = (seed>>16)/65536.0;
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seed=(seed+1)*3141592621u;
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}
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}
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}
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inline fltx4 RandSIMD( void )
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{
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// ret= rand[k]+rand[j]
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fltx4 retval=AddSIMD( *m_pRand_K, *m_pRand_J );
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// if ( ret>=1.0) ret-=1.0
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fltx4 overflow_mask=CmpGeSIMD( retval, Four_Ones );
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retval=SubSIMD( retval, AndSIMD( Four_Ones, overflow_mask ) );
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*m_pRand_K = retval;
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// update pointers w/ wrap-around
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if ( --m_pRand_J < m_RandY )
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m_pRand_J=m_RandY+54;
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if ( --m_pRand_K < m_RandY )
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m_pRand_K=m_RandY+54;
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return retval;
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}
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};
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#define MAX_SIMULTANEOUS_RANDOM_STREAMS 32
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static SIMDRandStreamContext s_SIMDRandContexts[MAX_SIMULTANEOUS_RANDOM_STREAMS];
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static volatile int s_nRandContextsInUse[MAX_SIMULTANEOUS_RANDOM_STREAMS];
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void SeedRandSIMD(uint32 seed)
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{
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for( int i = 0; i<MAX_SIMULTANEOUS_RANDOM_STREAMS; i++)
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s_SIMDRandContexts[i].Seed( seed+i );
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}
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fltx4 RandSIMD( int nContextIndex )
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{
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return s_SIMDRandContexts[nContextIndex].RandSIMD();
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}
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int GetSIMDRandContext( void )
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{
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for(;;)
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{
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for(int i=0; i < NELEMS( s_SIMDRandContexts ); i++)
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{
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if ( ! s_nRandContextsInUse[i] ) // available?
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{
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// try to take it!
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if ( ThreadInterlockedAssignIf( &( s_nRandContextsInUse[i]), 1, 0 ) )
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{
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return i; // done!
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}
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}
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}
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Assert(0); // why don't we have enough buffers?
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ThreadSleep();
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}
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}
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void ReleaseSIMDRandContext( int nContext )
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{
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s_nRandContextsInUse[ nContext ] = 0;
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}
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fltx4 RandSIMD( void )
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{
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return s_SIMDRandContexts[0].RandSIMD();
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}
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