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auto merge of #6058 : huonw/rust/rt-isaac-update, r=graydon

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The "unsigned 4 byte" `ub4`s are actually 8 bytes on 64-bit platforms
which mean that some bits > 2**32 were retained in calculations, these
would then "reappear" after a right shift and so the stream of random numbers
would differ on 32 bit vs 64 bit platforms.

http://burtleburtle.net/bob/c/randport.c
This commit is contained in:
bors 2013-04-26 21:57:35 -07:00
commit 8804b13bd2
2 changed files with 37 additions and 27 deletions
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41
src/rt/isaac/randport.cpp
View file

@ -6,6 +6,7 @@ MODIFIED:
970719: use context, not global variables, for internal state
980324: make a portable version
010626: Note this is public domain
100725: Mask on use of >32 bits, not on assignment: from Paul Eggert
------------------------------------------------------------------------------
*/
#ifndef STANDARD
@ -27,22 +28,22 @@ MODIFIED:
void isaac(randctx *ctx)
{
register ub4 a,b,x,y,*m,*mm,*m2,*r,*mend;
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;
a = ctx->randa; b = ctx->randb + (++ctx->randc);
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 & 0xffffffff) >>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);
rngstep( (a & 0xffffffff) >>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 & 0xffffffff) >>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);
rngstep( (a & 0xffffffff) >>16, a, b, mm, m, m2, r, x);
}
ctx->randb = b; ctx->randa = a;
}
@ -50,14 +51,14 @@ void isaac(randctx *ctx)
#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; \
a^=b<<11; d+=a; b+=c; \
b^=(c&0xffffffff)>>2; e+=b; c+=d; \
c^=d<<8; f+=c; d+=e; \
d^=(e&0xffffffff)>>16; g+=d; e+=f; \
e^=f<<10; h+=e; f+=g; \
f^=(g&0xffffffff)>>4; a+=f; g+=h; \
g^=h<<8; b+=g; h+=a; \
h^=(a&0xffffffff)>>9; c+=h; a+=b; \
}
/* if (flag==TRUE), then use the contents of randrsl[] to initialize mm[]. */
@ -81,8 +82,10 @@ void randinit(randctx *ctx, word 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];
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;
@ -90,8 +93,10 @@ void randinit(randctx *ctx, word flag)
/* 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];
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;

23
src/rt/isaac/standard.h
View file

@ -13,27 +13,32 @@ Standard definitions and types, Bob Jenkins
# include <stddef.h>
# define STDDEF
# endif
typedef unsigned long long ub8;
# ifndef STDINT
# include <stdint.h>
# define STDINT
# endif
typedef uint64_t ub8;
#define UB8MAXVAL 0xffffffffffffffffLL
#define UB8BITS 64
typedef signed long long sb8;
typedef int64_t sb8;
#define SB8MAXVAL 0x7fffffffffffffffLL
typedef unsigned long int ub4; /* unsigned 4-byte quantities */
typedef uint32_t ub4; /* unsigned 4-byte quantities */
#define UB4MAXVAL 0xffffffff
typedef signed long int sb4;
typedef int32_t sb4;
#define UB4BITS 32
#define SB4MAXVAL 0x7fffffff
typedef unsigned short int ub2;
typedef uint16_t ub2;
#define UB2MAXVAL 0xffff
#define UB2BITS 16
typedef signed short int sb2;
typedef int16_t sb2;
#define SB2MAXVAL 0x7fff
typedef unsigned char ub1;
typedef uint8_t ub1;
#define UB1MAXVAL 0xff
#define UB1BITS 8
typedef signed char sb1; /* signed 1-byte quantities */
typedef int8_t sb1; /* signed 1-byte quantities */
#define SB1MAXVAL 0x7f
typedef int word; /* fastest type available */
typedef int word; /* fastest type available */
#define bis(target,mask) ((target) |= (mask))
#define bic(target,mask) ((target) &= ~(mask))