/src/rt/isaac/randport.cpp

  1/*
  2------------------------------------------------------------------------------
  3rand.c: By Bob Jenkins.  My random number generator, ISAAC.  Public Domain
  4MODIFIED:
  5  960327: Creation (addition of randinit, really)
  6  970719: use context, not global variables, for internal state
  7  980324: make a portable version
  8  010626: Note this is public domain
  9------------------------------------------------------------------------------
 10*/
 11#ifndef STANDARD
 12#include "standard.h"
 13#endif
 14#ifndef RAND
 15#include "rand.h"
 16#endif
 17
 18
 19#define ind(mm,x)  ((mm)[(x>>2)&(RANDSIZ-1)])
 20#define rngstep(mix,a,b,mm,m,m2,r,x) \
 21{ \
 22  x = *m;  \
 23  a = ((a^(mix)) + *(m2++)) & 0xffffffff; \
 24  *(m++) = y = (ind(mm,x) + a + b) & 0xffffffff; \
 25  *(r++) = b = (ind(mm,y>>RANDSIZL) + x) & 0xffffffff; \
 26}
 27
 28void     isaac(randctx *ctx)
 29{
 30   register ub4 a,b,x,y,*m,*mm,*m2,*r,*mend;
 31   mm=ctx->randmem; r=ctx->randrsl;
 32   a = ctx->randa; b = (ctx->randb + (++ctx->randc)) & 0xffffffff;
 33   for (m = mm, mend = m2 = m+(RANDSIZ/2); m<mend; )
 34   {
 35      rngstep( a<<13, a, b, mm, m, m2, r, x);
 36      rngstep( a>>6 , a, b, mm, m, m2, r, x);
 37      rngstep( a<<2 , a, b, mm, m, m2, r, x);
 38      rngstep( a>>16, a, b, mm, m, m2, r, x);
 39   }
 40   for (m2 = mm; m2<mend; )
 41   {
 42      rngstep( a<<13, a, b, mm, m, m2, r, x);
 43      rngstep( a>>6 , a, b, mm, m, m2, r, x);
 44      rngstep( a<<2 , a, b, mm, m, m2, r, x);
 45      rngstep( a>>16, a, b, mm, m, m2, r, x);
 46   }
 47   ctx->randb = b; ctx->randa = a;
 48}
 49
 50
 51#define mix(a,b,c,d,e,f,g,h) \
 52{ \
 53   a^=b<<11; d+=a; b+=c; \
 54   b^=c>>2;  e+=b; c+=d; \
 55   c^=d<<8;  f+=c; d+=e; \
 56   d^=e>>16; g+=d; e+=f; \
 57   e^=f<<10; h+=e; f+=g; \
 58   f^=g>>4;  a+=f; g+=h; \
 59   g^=h<<8;  b+=g; h+=a; \
 60   h^=a>>9;  c+=h; a+=b; \
 61}
 62
 63/* if (flag==TRUE), then use the contents of randrsl[] to initialize mm[]. */
 64void randinit(randctx *ctx, word flag)
 65{
 66   word i;
 67   ub4 a,b,c,d,e,f,g,h;
 68   ub4 *m,*r;
 69   ctx->randa = ctx->randb = ctx->randc = 0;
 70   m=ctx->randmem;
 71   r=ctx->randrsl;
 72   a=b=c=d=e=f=g=h=0x9e3779b9;  /* the golden ratio */
 73
 74   for (i=0; i<4; ++i)          /* scramble it */
 75   {
 76     mix(a,b,c,d,e,f,g,h);
 77   }
 78
 79   if (flag)
 80   {
 81     /* initialize using the contents of r[] as the seed */
 82     for (i=0; i<RANDSIZ; i+=8)
 83     {
 84       a+=r[i  ]; b+=r[i+1]; c+=r[i+2]; d+=r[i+3];
 85       e+=r[i+4]; f+=r[i+5]; g+=r[i+6]; h+=r[i+7];
 86       mix(a,b,c,d,e,f,g,h);
 87       m[i  ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
 88       m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
 89     }
 90     /* do a second pass to make all of the seed affect all of m */
 91     for (i=0; i<RANDSIZ; i+=8)
 92     {
 93       a+=m[i  ]; b+=m[i+1]; c+=m[i+2]; d+=m[i+3];
 94       e+=m[i+4]; f+=m[i+5]; g+=m[i+6]; h+=m[i+7];
 95       mix(a,b,c,d,e,f,g,h);
 96       m[i  ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
 97       m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
 98     }
 99   }
100   else
101   {
102     for (i=0; i<RANDSIZ; i+=8)
103     {
104       /* fill in mm[] with messy stuff */
105       mix(a,b,c,d,e,f,g,h);
106       m[i  ]=a; m[i+1]=b; m[i+2]=c; m[i+3]=d;
107       m[i+4]=e; m[i+5]=f; m[i+6]=g; m[i+7]=h;
108     }
109   }
110
111   isaac(ctx);            /* fill in the first set of results */
112   ctx->randcnt=RANDSIZ;  /* prepare to use the first set of results */
113}
114
115
116#ifdef NEVER
117int main()
118{
119  ub4 i,j;
120  randctx ctx;
121  ctx.randa=ctx.randb=ctx.randc=(ub4)0;
122  for (i=0; i<256; ++i) ctx.randrsl[i]=(ub4)0;
123  randinit(&ctx, TRUE);
124  for (i=0; i<2; ++i)
125  {
126    isaac(&ctx);
127    for (j=0; j<256; ++j)
128    {
129      printf("%.8lx",ctx.randrsl[j]);
130      if ((j&7)==7) printf("\n");
131    }
132  }
133}
134#endif