408 lines
14 KiB
C
Executable File
408 lines
14 KiB
C
Executable File
/*
|
|
* Copyright (c) 1995, by Sun Microsystems, Inc.
|
|
* All rights reserved.
|
|
*/
|
|
|
|
/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
|
|
/* All Rights Reserved */
|
|
|
|
/* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T */
|
|
/* The copyright notice above does not evidence any */
|
|
/* actual or intended publication of such source code. */
|
|
|
|
#pragma ident "@(#)random.c 1.2 95/02/28 SMI" /* SVr4.0 1.3 */
|
|
|
|
/*******************************************************************
|
|
|
|
PROPRIETARY NOTICE (Combined)
|
|
|
|
This source code is unpublished proprietary information
|
|
constituting, or derived under license from AT&T's UNIX(r) System V.
|
|
In addition, portions of such source code were derived from Berkeley
|
|
4.3 BSD under license from the Regents of the University of
|
|
California.
|
|
|
|
|
|
|
|
Copyright Notice
|
|
|
|
Notice of copyright on this source code product does not indicate
|
|
publication.
|
|
|
|
(c) 1986,1987,1988,1989 Sun Microsystems, Inc
|
|
(c) 1983,1984,1985,1986,1987,1988,1989 AT&T.
|
|
All rights reserved.
|
|
********************************************************************/
|
|
|
|
/*LINTLIBRARY*/
|
|
#include "synonyms.h"
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
|
|
/*
|
|
* random.c:
|
|
* An improved random number generation package. In addition to the standard
|
|
* rand()/srand() like interface, this package also has a special state info
|
|
* interface. The initstate() routine is called with a seed, an array of
|
|
* bytes, and a count of how many bytes are being passed in; this array is then
|
|
* initialized to contain information for random number generation with that
|
|
* much state information. Good sizes for the amount of state information are
|
|
* 32, 64, 128, and 256 bytes. The state can be switched by calling the
|
|
* setstate() routine with the same array as was initiallized with initstate().
|
|
* By default, the package runs with 128 bytes of state information and
|
|
* generates far better random numbers than a linear congruential generator.
|
|
* If the amount of state information is less than 32 bytes, a simple linear
|
|
* congruential R.N.G. is used.
|
|
* Internally, the state information is treated as an array of longs; the
|
|
* zeroeth element of the array is the type of R.N.G. being used (small
|
|
* integer); the remainder of the array is the state information for the
|
|
* R.N.G. Thus, 32 bytes of state information will give 7 longs worth of
|
|
* state information, which will allow a degree seven polynomial. (Note: the
|
|
* zeroeth word of state information also has some other information stored
|
|
* in it -- see setstate() for details).
|
|
* The random number generation technique is a linear feedback shift register
|
|
* approach, employing trinomials (since there are fewer terms to sum up that
|
|
* way). In this approach, the least significant bit of all the numbers in
|
|
* the state table will act as a linear feedback shift register, and will have
|
|
* period 2^deg - 1 (where deg is the degree of the polynomial being used,
|
|
* assuming that the polynomial is irreducible and primitive). The higher
|
|
* order bits will have longer periods, since their values are also influenced
|
|
* by pseudo-random carries out of the lower bits. The total period of the
|
|
* generator is approximately deg*(2**deg - 1); thus doubling the amount of
|
|
* state information has a vast influence on the period of the generator.
|
|
* Note: the deg*(2**deg - 1) is an approximation only good for large deg,
|
|
* when the period of the shift register is the dominant factor. With deg
|
|
* equal to seven, the period is actually much longer than the 7*(2**7 - 1)
|
|
* predicted by this formula.
|
|
*/
|
|
|
|
|
|
|
|
/*
|
|
* For each of the currently supported random number generators, we have a
|
|
* break value on the amount of state information (you need at least this
|
|
* many bytes of state info to support this random number generator), a degree
|
|
* for the polynomial (actually a trinomial) that the R.N.G. is based on, and
|
|
* the separation between the two lower order coefficients of the trinomial.
|
|
*/
|
|
|
|
#define TYPE_0 0 /* linear congruential */
|
|
#define BREAK_0 8
|
|
#define DEG_0 0
|
|
#define SEP_0 0
|
|
|
|
#define TYPE_1 1 /* x**7 + x**3 + 1 */
|
|
#define BREAK_1 32
|
|
#define DEG_1 7
|
|
#define SEP_1 3
|
|
|
|
#define TYPE_2 2 /* x**15 + x + 1 */
|
|
#define BREAK_2 64
|
|
#define DEG_2 15
|
|
#define SEP_2 1
|
|
|
|
#define TYPE_3 3 /* x**31 + x**3 + 1 */
|
|
#define BREAK_3 128
|
|
#define DEG_3 31
|
|
#define SEP_3 3
|
|
|
|
#define TYPE_4 4 /* x**63 + x + 1 */
|
|
#define BREAK_4 256
|
|
#define DEG_4 63
|
|
#define SEP_4 1
|
|
|
|
|
|
/*
|
|
* Array versions of the above information to make code run faster -- relies
|
|
* on fact that TYPE_i == i.
|
|
*/
|
|
|
|
#define MAX_TYPES 5 /* max number of types above */
|
|
|
|
static struct _randomjunk {
|
|
int degrees[MAX_TYPES];
|
|
int seps[MAX_TYPES];
|
|
long randtbl[ DEG_3 + 1 ];
|
|
/*
|
|
* fptr and rptr are two pointers into the state info, a front and a rear
|
|
* pointer. These two pointers are always rand_sep places aparts, as they cycle
|
|
* cyclically through the state information. (Yes, this does mean we could get
|
|
* away with just one pointer, but the code for random() is more efficient this
|
|
* way). The pointers are left positioned as they would be from the call
|
|
* initstate( 1, randtbl, 128 )
|
|
* (The position of the rear pointer, rptr, is really 0 (as explained above
|
|
* in the initialization of randtbl) because the state table pointer is set
|
|
* to point to randtbl[1] (as explained below).
|
|
*/
|
|
long *fptr, *rptr;
|
|
/*
|
|
* The following things are the pointer to the state information table,
|
|
* the type of the current generator, the degree of the current polynomial
|
|
* being used, and the separation between the two pointers.
|
|
* Note that for efficiency of random(), we remember the first location of
|
|
* the state information, not the zeroeth. Hence it is valid to access
|
|
* state[-1], which is used to store the type of the R.N.G.
|
|
* Also, we remember the last location, since this is more efficient than
|
|
* indexing every time to find the address of the last element to see if
|
|
* the front and rear pointers have wrapped.
|
|
*/
|
|
long *state;
|
|
int rand_type, rand_deg, rand_sep;
|
|
long *end_ptr;
|
|
} *__randomjunk, *_randomjunk(), _randominit = {
|
|
/*
|
|
* Initially, everything is set up as if from :
|
|
* initstate( 1, &randtbl, 128 );
|
|
* Note that this initialization takes advantage of the fact
|
|
* that srandom() advances the front and rear pointers 10*rand_deg
|
|
* times, and hence the rear pointer which starts at 0 will also
|
|
* end up at zero; thus the zeroeth element of the state
|
|
* information, which contains info about the current
|
|
* position of the rear pointer is just
|
|
* MAX_TYPES*(rptr - state) + TYPE_3 == TYPE_3.
|
|
*/
|
|
{ DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 },
|
|
{ SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 },
|
|
{ TYPE_3,
|
|
0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342,
|
|
0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb,
|
|
0x7449e56b, 0xbeb1dbb0, 0xab5c5918, 0x946554fd,
|
|
0x8c2e680f, 0xeb3d799f, 0xb11ee0b7, 0x2d436b86,
|
|
0xda672e2a, 0x1588ca88, 0xe369735d, 0x904f35f7,
|
|
0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc,
|
|
0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b,
|
|
0xf5ad9d0e, 0x8999220b, 0x27fb47b9 },
|
|
&_randominit.randtbl[ SEP_3 + 1 ],
|
|
&_randominit.randtbl[ 1 ],
|
|
&_randominit.randtbl[ 1 ],
|
|
TYPE_3, DEG_3, SEP_3,
|
|
&_randominit.randtbl[ DEG_3 + 1]
|
|
};
|
|
|
|
static struct _randomjunk *
|
|
_randomjunk(void)
|
|
{
|
|
register struct _randomjunk *rp = __randomjunk;
|
|
|
|
if (rp == 0) {
|
|
rp = (struct _randomjunk *)malloc(sizeof (*rp));
|
|
if (rp == 0)
|
|
return (0);
|
|
*rp = _randominit;
|
|
__randomjunk = rp;
|
|
}
|
|
return (rp);
|
|
}
|
|
|
|
/*
|
|
* srandom:
|
|
* Initialize the random number generator based on the given seed. If the
|
|
* type is the trivial no-state-information type, just remember the seed.
|
|
* Otherwise, initializes state[] based on the given "seed" via a linear
|
|
* congruential generator. Then, the pointers are set to known locations
|
|
* that are exactly rand_sep places apart. Lastly, it cycles the state
|
|
* information a given number of times to get rid of any initial dependencies
|
|
* introduced by the L.C.R.N.G.
|
|
* Note that the initialization of randtbl[] for default usage relies on
|
|
* values produced by this routine.
|
|
*/
|
|
|
|
void
|
|
srandom(unsigned int x)
|
|
{
|
|
register struct _randomjunk *rp = _randomjunk();
|
|
register int i, j;
|
|
extern long random(void);
|
|
|
|
if (rp == 0)
|
|
return;
|
|
if( rp->rand_type == TYPE_0 ) {
|
|
rp->state[ 0 ] = x;
|
|
}
|
|
else {
|
|
j = 1;
|
|
rp->state[ 0 ] = x;
|
|
for( i = 1; i < rp->rand_deg; i++ ) {
|
|
rp->state[i] = 1103515245*rp->state[i - 1] + 12345;
|
|
}
|
|
rp->fptr = &rp->state[ rp->rand_sep ];
|
|
rp->rptr = &rp->state[ 0 ];
|
|
for( i = 0; i < 10*rp->rand_deg; i++ ) (void)random();
|
|
}
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
* initstate:
|
|
* Initialize the state information in the given array of n bytes for
|
|
* future random number generation. Based on the number of bytes we
|
|
* are given, and the break values for the different R.N.G.'s, we choose
|
|
* the best (largest) one we can and set things up for it. srandom() is
|
|
* then called to initialize the state information.
|
|
* Note that on return from srandom(), we set state[-1] to be the type
|
|
* multiplexed with the current value of the rear pointer; this is so
|
|
* successive calls to initstate() won't lose this information and will
|
|
* be able to restart with setstate().
|
|
* Note: the first thing we do is save the current state, if any, just like
|
|
* setstate() so that it doesn't matter when initstate is called.
|
|
* Returns a pointer to the old state.
|
|
*/
|
|
|
|
char *
|
|
initstate(
|
|
unsigned int seed, /* seed for R. N. G. */
|
|
char *arg_state, /* pointer to state array */
|
|
size_t n) /* # bytes of state info */
|
|
{
|
|
register struct _randomjunk *rp = _randomjunk();
|
|
register char *ostate;
|
|
|
|
if (rp == 0)
|
|
return (0);
|
|
ostate = (char *)( &rp->state[ -1 ] );
|
|
|
|
if( rp->rand_type == TYPE_0 ) rp->state[ -1 ] = rp->rand_type;
|
|
else rp->state[ -1 ] =
|
|
MAX_TYPES*(rp->rptr - rp->state) + rp->rand_type;
|
|
if( n < BREAK_1 ) {
|
|
if( n < BREAK_0 ) {
|
|
fprintf( stderr, "initstate: not enough state (%d bytes) with which to do jack; ignored.\n", n);
|
|
return (0);
|
|
}
|
|
rp->rand_type = TYPE_0;
|
|
rp->rand_deg = DEG_0;
|
|
rp->rand_sep = SEP_0;
|
|
}
|
|
else {
|
|
if( n < BREAK_2 ) {
|
|
rp->rand_type = TYPE_1;
|
|
rp->rand_deg = DEG_1;
|
|
rp->rand_sep = SEP_1;
|
|
}
|
|
else {
|
|
if( n < BREAK_3 ) {
|
|
rp->rand_type = TYPE_2;
|
|
rp->rand_deg = DEG_2;
|
|
rp->rand_sep = SEP_2;
|
|
}
|
|
else {
|
|
if( n < BREAK_4 ) {
|
|
rp->rand_type = TYPE_3;
|
|
rp->rand_deg = DEG_3;
|
|
rp->rand_sep = SEP_3;
|
|
}
|
|
else {
|
|
rp->rand_type = TYPE_4;
|
|
rp->rand_deg = DEG_4;
|
|
rp->rand_sep = SEP_4;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
rp->state = &( ( (long *)arg_state )[1] ); /* first location */
|
|
rp->end_ptr = &rp->state[ rp->rand_deg ]; /* must set end_ptr before srandom */
|
|
srandom( seed );
|
|
if( rp->rand_type == TYPE_0 ) rp->state[ -1 ] = rp->rand_type;
|
|
else rp->state[ -1 ] = MAX_TYPES*(rp->rptr - rp->state) + rp->rand_type;
|
|
return( ostate );
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
* setstate:
|
|
* Restore the state from the given state array.
|
|
* Note: it is important that we also remember the locations of the pointers
|
|
* in the current state information, and restore the locations of the pointers
|
|
* from the old state information. This is done by multiplexing the pointer
|
|
* location into the zeroeth word of the state information.
|
|
* Note that due to the order in which things are done, it is OK to call
|
|
* setstate() with the same state as the current state.
|
|
* Returns a pointer to the old state information.
|
|
*/
|
|
|
|
char *
|
|
setstate(const char *arg_state)
|
|
{
|
|
register struct _randomjunk *rp = _randomjunk();
|
|
register long *new_state;
|
|
register int type;
|
|
register int rear;
|
|
char *ostate;
|
|
|
|
if (rp == 0)
|
|
return (0);
|
|
new_state = (long *)arg_state;
|
|
type = new_state[0]%MAX_TYPES;
|
|
rear = new_state[0]/MAX_TYPES;
|
|
ostate = (char *)( &rp->state[ -1 ] );
|
|
|
|
if( rp->rand_type == TYPE_0 ) rp->state[ -1 ] = rp->rand_type;
|
|
else rp->state[ -1 ] = MAX_TYPES*(rp->rptr - rp->state) + rp->rand_type;
|
|
switch( type ) {
|
|
case TYPE_0:
|
|
case TYPE_1:
|
|
case TYPE_2:
|
|
case TYPE_3:
|
|
case TYPE_4:
|
|
rp->rand_type = type;
|
|
rp->rand_deg = rp->degrees[ type ];
|
|
rp->rand_sep = rp->seps[ type ];
|
|
break;
|
|
|
|
default:
|
|
fprintf( stderr, "setstate: state info has been munged; not changed.\n" );
|
|
}
|
|
rp->state = &new_state[ 1 ];
|
|
if( rp->rand_type != TYPE_0 ) {
|
|
rp->rptr = &rp->state[ rear ];
|
|
rp->fptr = &rp->state[ (rear + rp->rand_sep)%rp->rand_deg ];
|
|
}
|
|
rp->end_ptr = &rp->state[ rp->rand_deg ]; /* set end_ptr too */
|
|
return( ostate );
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
* random:
|
|
* If we are using the trivial TYPE_0 R.N.G., just do the old linear
|
|
* congruential bit. Otherwise, we do our fancy trinomial stuff, which is the
|
|
* same in all ther other cases due to all the global variables that have been
|
|
* set up. The basic operation is to add the number at the rear pointer into
|
|
* the one at the front pointer. Then both pointers are advanced to the next
|
|
* location cyclically in the table. The value returned is the sum generated,
|
|
* reduced to 31 bits by throwing away the "least random" low bit.
|
|
* Note: the code takes advantage of the fact that both the front and
|
|
* rear pointers can't wrap on the same call by not testing the rear
|
|
* pointer if the front one has wrapped.
|
|
* Returns a 31-bit random number.
|
|
*/
|
|
|
|
long
|
|
random(void)
|
|
{
|
|
register struct _randomjunk *rp = _randomjunk();
|
|
long i;
|
|
|
|
if (rp == 0)
|
|
return (0);
|
|
if( rp->rand_type == TYPE_0 ) {
|
|
i = rp->state[0] = ( rp->state[0]*1103515245 + 12345 )&0x7fffffff;
|
|
}
|
|
else {
|
|
*rp->fptr += *rp->rptr;
|
|
i = (*rp->fptr >> 1)&0x7fffffff; /* chucking least random bit */
|
|
if( ++rp->fptr >= rp->end_ptr ) {
|
|
rp->fptr = rp->state;
|
|
++rp->rptr;
|
|
}
|
|
else {
|
|
if( ++rp->rptr >= rp->end_ptr ) rp->rptr = rp->state;
|
|
}
|
|
}
|
|
return( i );
|
|
}
|