/* rng/ranlxs.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 James Theiler, Brian Gough
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <config.h>
#include <stdlib.h>
#include <gsl/gsl_rng.h>
/* This is an implementation of M. Luescher's second generation
version of the RANLUX generator.
Thanks to Martin Luescher for providing information on this
generator.
*/
static unsigned long int ranlxs_get (void *vstate);
static inline double ranlxs_get_double (void *vstate);
static void ranlxs_set_lux (void *state, unsigned long int s, unsigned int luxury);
static void ranlxs0_set (void *state, unsigned long int s);
static void ranlxs1_set (void *state, unsigned long int s);
static void ranlxs2_set (void *state, unsigned long int s);
static const int next[12] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 0};
static const int snext[24] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 0};
static const double sbase = 16777216.0; /* 2^24 */
static const double sone_bit = 1.0 / 16777216.0; /* 1/2^24 */
static const double one_bit = 1.0 / 281474976710656.0; /* 1/2^48 */
static const double shift = 268435456.0; /* 2^28 */
#define RANLUX_STEP(x1,x2,i1,i2,i3) \
x1=xdbl[i1] - xdbl[i2]; \
if (x2 < 0) \
{ \
x1-=one_bit; \
x2+=1; \
} \
xdbl[i3]=x2
typedef struct
{
double xdbl[12], ydbl[12]; /* doubles first so they are 8-byte aligned */
double carry;
float xflt[24];
unsigned int ir;
unsigned int jr;
unsigned int is;
unsigned int is_old;
unsigned int pr;
}
ranlxs_state_t;
static void increment_state (ranlxs_state_t * state);
static void
increment_state (ranlxs_state_t * state)
{
int k, kmax, m;
double x, y1, y2, y3;
float *xflt = state->xflt;
double *xdbl = state->xdbl;
double *ydbl = state->ydbl;
double carry = state->carry;
unsigned int ir = state->ir;
unsigned int jr = state->jr;
for (k = 0; ir > 0; ++k)
{
y1 = xdbl[jr] - xdbl[ir];
y2 = y1 - carry;
if (y2 < 0)
{
carry = one_bit;
y2 += 1;
}
else
{
carry = 0;
}
xdbl[ir] = y2;
ir = next[ir];
jr = next[jr];
}
kmax = state->pr - 12;
for (; k <= kmax; k += 12)
{
y1 = xdbl[7] - xdbl[0];
y1 -= carry;
RANLUX_STEP (y2, y1, 8, 1, 0);
RANLUX_STEP (y3, y2, 9, 2, 1);
RANLUX_STEP (y1, y3, 10, 3, 2);
RANLUX_STEP (y2, y1, 11, 4, 3);
RANLUX_STEP (y3, y2, 0, 5, 4);
RANLUX_STEP (y1, y3, 1, 6, 5);
RANLUX_STEP (y2, y1, 2, 7, 6);
RANLUX_STEP (y3, y2, 3, 8, 7);
RANLUX_STEP (y1, y3, 4, 9, 8);
RANLUX_STEP (y2, y1, 5, 10, 9);
RANLUX_STEP (y3, y2, 6, 11, 10);
if (y3 < 0)
{
carry = one_bit;
y3 += 1;
}
else
{
carry = 0;
}
xdbl[11] = y3;
}
kmax = state->pr;
for (; k < kmax; ++k)
{
y1 = xdbl[jr] - xdbl[ir];
y2 = y1 - carry;
if (y2 < 0)
{
carry = one_bit;
y2 += 1;
}
else
{
carry = 0;
}
xdbl[ir] = y2;
ydbl[ir] = y2 + shift;
ir = next[ir];
jr = next[jr];
}
ydbl[ir] = xdbl[ir] + shift;
for (k = next[ir]; k > 0;)
{
ydbl[k] = xdbl[k] + shift;
k = next[k];
}
for (k = 0, m = 0; k < 12; ++k)
{
x = xdbl[k];
y2 = ydbl[k] - shift;
if (y2 > x)
y2 -= sone_bit;
y1 = (x - y2) * sbase;
xflt[m++] = (float) y1;
xflt[m++] = (float) y2;
}
state->ir = ir;
state->is = 2 * ir;
state->is_old = 2 * ir;
state->jr = jr;
state->carry = carry;
}
static inline double
ranlxs_get_double (void *vstate)
{
ranlxs_state_t *state = (ranlxs_state_t *) vstate;
const unsigned int is = snext[state->is];
state->is = is;
if (is == state->is_old)
increment_state (state);
return state->xflt[state->is];
}
static unsigned long int
ranlxs_get (void *vstate)
{
return ranlxs_get_double (vstate) * 16777216.0; /* 2^24 */
}
static void
ranlxs_set_lux (void *vstate, unsigned long int s, unsigned int luxury)
{
ranlxs_state_t *state = (ranlxs_state_t *) vstate;
int ibit, jbit, i, k, m, xbit[31];
double x, y;
long int seed;
if (s == 0)
s = 1; /* default seed is 1 */
seed = s;
i = seed & 0x7FFFFFFFUL; /* Allowed seeds for ranlxs are 0 .. 2^31-1 */
for (k = 0; k < 31; ++k)
{
xbit[k] = i % 2;
i /= 2;
}
ibit = 0;
jbit = 18;
for (k = 0; k < 12; ++k)
{
x = 0;
for (m = 1; m <= 48; ++m)
{
y = (double) xbit[ibit];
x += x + y;
xbit[ibit] = (xbit[ibit] + xbit[jbit]) % 2;
ibit = (ibit + 1) % 31;
jbit = (jbit + 1) % 31;
}
state->xdbl[k] = one_bit * x;
}
state->carry = 0;
state->ir = 0;
state->jr = 7;
state->is = 23;
state->is_old = 0;
state->pr = luxury;
}
static void
ranlxs0_set (void *vstate, unsigned long int s)
{
ranlxs_set_lux (vstate, s, 109);
}
void
ranlxs1_set (void *vstate, unsigned long int s)
{
ranlxs_set_lux (vstate, s, 202);
}
static void
ranlxs2_set (void *vstate, unsigned long int s)
{
ranlxs_set_lux (vstate, s, 397);
}
static const gsl_rng_type ranlxs0_type =
{"ranlxs0", /* name */
0x00ffffffUL, /* RAND_MAX */
0, /* RAND_MIN */
sizeof (ranlxs_state_t),
&ranlxs0_set,
&ranlxs_get,
&ranlxs_get_double};
static const gsl_rng_type ranlxs1_type =
{"ranlxs1", /* name */
0x00ffffffUL, /* RAND_MAX */
0, /* RAND_MIN */
sizeof (ranlxs_state_t),
&ranlxs1_set,
&ranlxs_get,
&ranlxs_get_double};
static const gsl_rng_type ranlxs2_type =
{"ranlxs2", /* name */
0x00ffffffUL, /* RAND_MAX */
0, /* RAND_MIN */
sizeof (ranlxs_state_t),
&ranlxs2_set,
&ranlxs_get,
&ranlxs_get_double};
const gsl_rng_type *gsl_rng_ranlxs0 = &ranlxs0_type;
const gsl_rng_type *gsl_rng_ranlxs1 = &ranlxs1_type;
const gsl_rng_type *gsl_rng_ranlxs2 = &ranlxs2_type;