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Replace PRNG with a standard MT.

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RandomGen r; r(); now generates [0,2^31-1] on 32-bit platforms,
not [0,2^31-2].  No longer uses MAX_INT, so the default behavior
doesn't depend on the size of an int.

RandomInt no longer generates a float and truncates it.  That
limited the values that could be returned to those that fit in
a 32-bit float.

Remove NR code.  It's not free.

This code is not threadsafe.  Locking access would kill performance.
The old code wasn't, either.  I think most symptoms would be
innocuous enough to not worry about.
This commit is contained in:
Glenn Maynard
2006-10-18 02:28:06 +00:00
parent 08ca0d7721
commit f7f21e2b8c
2 changed files with 85 additions and 45 deletions
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stepmania/src/RageUtil.cpp
+56 -32
View File
@@ -15,51 +15,75 @@
#include <sys/stat.h>
#include <float.h>
int randseed = time(NULL);
RandomGen g_RandomNumberGenerator;
// From "Numerical Recipes in C".
static float RandomFloatFromSeed( int &seed )
MersenneTwister::MersenneTwister( int iSeed )
{
const int MASK = 123459876;
seed ^= MASK;
const int IA = 16807;
const int IM = 2147483647;
const int IQ = 127773;
const int IR = 2836;
long k = seed / IQ;
seed = IA*(seed-k*IQ)-IR*k;
if( seed < 0 )
seed += IM;
const float AM = .999999f / IM;
float ans = AM * seed;
seed ^= MASK;
return ans;
Reset( iSeed );
}
float RandomFloat()
void MersenneTwister::Reset( int iSeed )
{
return RandomFloatFromSeed( randseed );
if( iSeed == 0 )
iSeed = time(NULL);
m_Values[0] = iSeed;
m_iNext = 0;
for( int i = 1; i < 624; ++i )
m_Values[i] = ((69069 * m_Values[i-1]) + 1) & 0xFFFFFFFF;
GenerateValues();
}
RandomGen::RandomGen( unsigned long seed_ )
void MersenneTwister::GenerateValues()
{
seed = seed_;
if(seed == 0)
seed = time(NULL);
static const int mask[] = { 0, 0x9908B0DF };
for( int i = 0; i < 227; ++i )
{
int iVal = (m_Values[i] & 0x80000000) | (m_Values[i+1] & 0x7FFFFFFF);
int iNext = (i + 397);
m_Values[i] = m_Values[iNext];
m_Values[i] ^= (iVal >> 1);
m_Values[i] ^= mask[iVal&1];
}
for( int i = 227; i < 623; ++i )
{
int iVal = (m_Values[i] & 0x80000000) | (m_Values[i+1] & 0x7FFFFFFF);
int iNext = (i + 397) - 624;
m_Values[i] = m_Values[iNext];
m_Values[i] ^= (iVal >> 1);
m_Values[i] ^= mask[iVal&1];
}
int iVal = (m_Values[623] & 0x80000000) + (m_Values[0] & 0x7FFFFFFF);
int iNext = (623 + 397) - 624;
m_Values[623] = m_Values[iNext] ^ (iVal>>1);
m_Values[623] ^= mask[iVal&1];
}
int RandomGen::operator() ( int n )
int MersenneTwister::Temper( int iVal )
{
float f = RandomFloatFromSeed(seed) * (n);
int ans = int(f);
return ans;
iVal ^= (iVal >> 11);
iVal ^= (iVal << 7) & 0x9D2C5680;
iVal ^= (iVal << 15) & 0xEFC60000;
iVal ^= (iVal >> 18);
return iVal;
}
int MersenneTwister::operator()()
{
if( m_iNext == 624 )
{
m_iNext = 0;
GenerateValues();
}
return Temper( m_Values[m_iNext++] );
}
void fapproach( float& val, float other_val, float to_move )
{