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Diffstat (limited to 'isaac.c')
| -rw-r--r-- | isaac.c | 110 |
1 files changed, 110 insertions, 0 deletions
@@ -0,0 +1,110 @@ +/* +------------------------------------------------------------------------------ +isaac.c: By Bob Jenkins. My random number generator, ISAAC. +MODIFIED: + 960327: Creation (addition of randinit, really) + 970719: use context, not global variables, for internal state + 980324: make a portable version + 991209: modified for inclusion with GNU Backgammon by Gary Wong + 070121: modified for inclusion with flam3 by Erik Reckase +------------------------------------------------------------------------------ +*/ + +#include "isaacs.h" +#include "isaac.h" + +#define ind(mm,x) ((mm)[(x>>2)&(RANDSIZ-1)]) +#define rngstep(mix,a,b,mm,m,m2,r,x) \ +{ \ + x = *m; \ + a = ((a^(mix)) + *(m2++)) & 0xffffffff; \ + *(m++) = y = (ind(mm,x) + a + b) & 0xffffffff; \ + *(r++) = b = (ind(mm,y>>RANDSIZL) + x) & 0xffffffff; \ +} + +void isaac(randctx *ctx) +{ + register ub4 a,b,x,y,*m,*mm,*m2,*r,*mend; + mm=ctx->randmem; r=ctx->randrsl; + a = ctx->randa; b = (ctx->randb + (++ctx->randc)) & 0xffffffff; + for (m = mm, mend = m2 = m+(RANDSIZ/2); m<mend; ) + { + rngstep( a<<13, a, b, mm, m, m2, r, x); + rngstep( a>>6 , a, b, mm, m, m2, r, x); + rngstep( a<<2 , a, b, mm, m, m2, r, x); + rngstep( a>>16, a, b, mm, m, m2, r, x); + } + for (m2 = mm; m2<mend; ) + { + rngstep( a<<13, a, b, mm, m, m2, r, x); + rngstep( a>>6 , a, b, mm, m, m2, r, x); + rngstep( a<<2 , a, b, mm, m, m2, r, x); + rngstep( a>>16, a, b, mm, m, m2, r, x); + } + ctx->randb = b; ctx->randa = a; +} + + +#define mix(a,b,c,d,e,f,g,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; \ +} + +/* if (flag==TRUE), then use the contents of randrsl[] to initialize mm[]. */ +void irandinit(randctx *ctx, word flag) +{ + word i; + ub4 a,b,c,d,e,f,g,h; + ub4 *m,*r; + ctx->randa = ctx->randb = ctx->randc = 0; + m=ctx->randmem; + r=ctx->randrsl; + a=b=c=d=e=f=g=h=0x9e3779b9; /* the golden ratio */ + + for (i=0; i<4; ++i) /* scramble it */ + { + mix(a,b,c,d,e,f,g,h); + } + + if (flag) + { + /* initialize using the contents of r[] as the seed */ + for (i=0; i<RANDSIZ; 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]; + mix(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<RANDSIZ; 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]; + mix(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 + { + for (i=0; i<RANDSIZ; i+=8) + { + /* fill in mm[] with messy stuff */ + mix(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=RANDSIZ; /* prepare to use the first set of results */ +} |