1 files changed, 109 insertions, 0 deletions
diff --git a/mathlib/randsse.cpp b/mathlib/randsse.cpp
new file mode 100644
index 0000000..b718d39
--- /dev/null
+++ b/mathlib/randsse.cpp
@@ -0,0 +1,109 @@
+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// 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();
+}