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#ifndef __ISAAC_HPP
#define __ISAAC_HPP
/*
C++ TEMPLATE VERSION OF Robert J. Jenkins Jr.'s
ISAAC Random Number Generator.
Ported from vanilla C to to template C++ class
by Quinn Tyler Jackson on 16-23 July 1998.
quinn@qtj.net
The function for the expected period of this
random number generator, according to Jenkins is:
f(a,b) = 2**((a+b*(3+2^^a)-1)
(where a is ALPHA and b is bitwidth)
So, for a bitwidth of 32 and an ALPHA of 8,
the expected period of ISAAC is:
2^^(8+32*(3+2^^8)-1) = 2^^8295
Jackson has been able to run implementations
with an ALPHA as high as 16, or
2^^2097263
*/
typedef unsigned int UINT32;
const UINT32 GOLDEN_RATIO = UINT32(0x9e3779b9);
template <UINT32 ALPHA = (8)>
class QTIsaac
{
public:
typedef unsigned char byte;
struct randctx
{
randctx(void)
{
randrsl = new UINT32[N];
randmem = new UINT32[N];
}
~randctx(void)
{
delete [] randrsl;
delete [] randmem;
}
UINT32 randcnt;
UINT32* randrsl;
UINT32* randmem;
UINT32 randa;
UINT32 randb;
UINT32 randc;
};
QTIsaac(UINT32 a = 0, UINT32 b = 0, UINT32 c = 0);
virtual ~QTIsaac(void);
UINT32 rand(void);
virtual void randinit(randctx* ctx, bool bUseSeed);
virtual void srand(
UINT32 a = 0, UINT32 b = 0, UINT32 c = 0, UINT32* s = NULL);
enum {N = (1<<ALPHA)};
protected:
virtual void isaac(randctx* ctx);
UINT32 ind(UINT32* mm, UINT32 x);
void rngstep(
UINT32 mix, UINT32& a, UINT32& b, UINT32*& mm, UINT32*& m,
UINT32*& m2, UINT32*& r, UINT32& x, UINT32& y);
virtual void shuffle(
UINT32& a, UINT32& b, UINT32& c, UINT32& d, UINT32& e, UINT32& f,
UINT32& g, UINT32& h);
private:
randctx m_rc;
};
template<UINT32 ALPHA>
QTIsaac<ALPHA>::QTIsaac(UINT32 a, UINT32 b, UINT32 c) : m_rc()
{
srand(a, b, c);
}
template<UINT32 ALPHA>
QTIsaac<ALPHA>::~QTIsaac(void)
{
// DO NOTHING
}
template<UINT32 ALPHA>
void QTIsaac<ALPHA>::srand(UINT32 a, UINT32 b, UINT32 c, UINT32* s)
{
for(int i = 0; i < N; i++)
{
m_rc.randrsl[i] = s != NULL ? s[i] : 0;
}
m_rc.randa = a;
m_rc.randb = b;
m_rc.randc = c;
randinit(&m_rc, true);
}
template<UINT32 ALPHA>
inline UINT32 QTIsaac<ALPHA>::rand(void)
{
return 0x7fffffff & (!m_rc.randcnt-- ?
(isaac(&m_rc), m_rc.randcnt=(N-1), m_rc.randrsl[m_rc.randcnt]) :
m_rc.randrsl[m_rc.randcnt]);
}
template<UINT32 ALPHA>
inline void QTIsaac<ALPHA>::randinit(randctx* ctx, bool bUseSeed)
{
UINT32 a,b,c,d,e,f,g,h;
int i;
a = b = c = d = e = f = g = h = GOLDEN_RATIO;
UINT32* m = (ctx->randmem);
UINT32* r = (ctx->randrsl);
if(!bUseSeed)
{
ctx->randa = 0;
ctx->randb = 0;
ctx->randc = 0;
}
// scramble it
for(i=0; i < 4; ++i)
{
shuffle(a,b,c,d,e,f,g,h);
}
if(bUseSeed)
{
// initialize using the contents of r[] as the seed
for(i=0; i < N; i+=8)
{
a+=r[i ]; b+=r[i+1]; c+=r[i+2]; d+=r[i+3];
e+=r[i+4]; f+=r[i+5]; g+=r[i+6]; h+=r[i+7];
shuffle(a,b,c,d,e,f,g,h);
m[i ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
}
//do a second pass to make all of the seed affect all of m
for(i=0; i < N; i += 8)
{
a+=m[i ]; b+=m[i+1]; c+=m[i+2]; d+=m[i+3];
e+=m[i+4]; f+=m[i+5]; g+=m[i+6]; h+=m[i+7];
shuffle(a,b,c,d,e,f,g,h);
m[i ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
}
}
else
{
// fill in mm[] with messy stuff
shuffle(a,b,c,d,e,f,g,h);
m[i ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
}
isaac(ctx); // fill in the first set of results
ctx->randcnt = N; // prepare to use the first set of results
}
template<UINT32 ALPHA>
inline UINT32 QTIsaac<ALPHA>::ind(UINT32* mm, UINT32 x)
{
return (*(UINT32*)((byte*)(mm) + ((x) & ((N-1)<<2))));
}
template<UINT32 ALPHA>
inline void QTIsaac<ALPHA>::rngstep(UINT32 mix, UINT32& a, UINT32& b, UINT32*& mm, UINT32*& m, UINT32*& m2, UINT32*& r, UINT32& x, UINT32& y)
{
x = *m;
a = (a^(mix)) + *(m2++);
*(m++) = y = ind(mm,x) + a + b;
*(r++) = b = ind(mm,y>>ALPHA) + x;
}
template<UINT32 ALPHA>
inline void QTIsaac<ALPHA>::shuffle(UINT32& a, UINT32& b, UINT32& c, UINT32& d, UINT32& e, UINT32& f, UINT32& g, UINT32& h)
{
a^=b<<11; d+=a; b+=c;
b^=c>>2; e+=b; c+=d;
c^=d<<8; f+=c; d+=e;
d^=e>>16; g+=d; e+=f;
e^=f<<10; h+=e; f+=g;
f^=g>>4; a+=f; g+=h;
g^=h<<8; b+=g; h+=a;
h^=a>>9; c+=h; a+=b;
}
template<UINT32 ALPHA>
inline void QTIsaac<ALPHA>::isaac(randctx* ctx)
{
UINT32 x,y;
UINT32* mm = ctx->randmem;
UINT32* r = ctx->randrsl;
UINT32 a = (ctx->randa);
UINT32 b = (ctx->randb + (++ctx->randc));
UINT32* m = mm;
UINT32* m2 = (m+(N/2));
UINT32* mend = m2;
for(; m<mend; )
{
rngstep((a<<13), a, b, mm, m, m2, r, x, y);
rngstep((a>>6) , a, b, mm, m, m2, r, x, y);
rngstep((a<<2) , a, b, mm, m, m2, r, x, y);
rngstep((a>>16), a, b, mm, m, m2, r, x, y);
}
m2 = mm;
for(; m2<mend; )
{
rngstep((a<<13), a, b, mm, m, m2, r, x, y);
rngstep((a>>6) , a, b, mm, m, m2, r, x, y);
rngstep((a<<2) , a, b, mm, m, m2, r, x, y);
rngstep((a>>16), a, b, mm, m, m2, r, x, y);
}
ctx->randb = b;
ctx->randa = a;
}
#endif // __ISAAC_HPP
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