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110 lines
2.3 KiB
C++
110 lines
2.3 KiB
C++
//========= Copyright <20> 1996-2006, 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 "core/stdafx.h"
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#include "tier0/dbg.h"
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#include "tier0/threadtools.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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bi32x4 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 LONG 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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ThreadMemoryBarrier();
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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(0);
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}
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}
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void ReleaseSIMDRandContext(int nContext)
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{
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ThreadMemoryBarrier();
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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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