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- /* rng/ranlxd.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 "gsl__config.h"
- #include <stdlib.h>
- #include "gsl_rng.h"
- /* This is an implementation of Martin Luescher's second generation
- double-precision (48-bit) version of the RANLUX generator.
- Thanks to Martin Luescher for providing information on this
- generator.
- */
- static inline unsigned long int ranlxd_get (void *vstate);
- static double ranlxd_get_double (void *vstate);
- static void ranlxd_set_lux (void *state, unsigned long int s, unsigned int luxury);
- static void ranlxd1_set (void *state, unsigned long int s);
- static void ranlxd2_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 double one_bit = 1.0 / 281474976710656.0; /* 1/2^48 */
- #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];
- double carry;
- unsigned int ir;
- unsigned int jr;
- unsigned int ir_old;
- unsigned int pr;
- }
- ranlxd_state_t;
- static inline void increment_state (ranlxd_state_t * state);
- static inline void
- increment_state (ranlxd_state_t * state)
- {
- int k, kmax;
- double y1, y2, y3;
- double *xdbl = state->xdbl;
- 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;
- ir = next[ir];
- jr = next[jr];
- }
- state->ir = ir;
- state->ir_old = ir;
- state->jr = jr;
- state->carry = carry;
- }
- static inline unsigned long int
- ranlxd_get (void *vstate)
- {
- return ranlxd_get_double (vstate) * 4294967296.0; /* 2^32 */
- }
- static double
- ranlxd_get_double (void *vstate)
- {
- ranlxd_state_t *state = (ranlxd_state_t *) vstate;
- int ir = state->ir;
- state->ir = next[ir];
- if (state->ir == state->ir_old)
- increment_state (state);
- return state->xdbl[state->ir];
- }
- static void
- ranlxd_set_lux (void *vstate, unsigned long int s, unsigned int luxury)
- {
- ranlxd_state_t *state = (ranlxd_state_t *) vstate;
- int ibit, jbit, i, k, l, xbit[31];
- double x, y;
- long int seed;
- if (s == 0)
- s = 1; /* default seed is 1 */
- seed = s;
- i = seed & 0xFFFFFFFFUL;
- 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 (l = 1; l <= 48; ++l)
- {
- y = (double) ((xbit[ibit] + 1) % 2);
- 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 = 11;
- state->jr = 7;
- state->ir_old = 0;
- state->pr = luxury;
- }
- static void
- ranlxd1_set (void *vstate, unsigned long int s)
- {
- ranlxd_set_lux (vstate, s, 202);
- }
- static void
- ranlxd2_set (void *vstate, unsigned long int s)
- {
- ranlxd_set_lux (vstate, s, 397);
- }
- static const gsl_rng_type ranlxd1_type =
- {"ranlxd1", /* name */
- 0xffffffffUL, /* RAND_MAX */
- 0, /* RAND_MIN */
- sizeof (ranlxd_state_t),
- &ranlxd1_set,
- &ranlxd_get,
- &ranlxd_get_double};
- static const gsl_rng_type ranlxd2_type =
- {"ranlxd2", /* name */
- 0xffffffffUL, /* RAND_MAX */
- 0, /* RAND_MIN */
- sizeof (ranlxd_state_t),
- &ranlxd2_set,
- &ranlxd_get,
- &ranlxd_get_double};
- const gsl_rng_type *gsl_rng_ranlxd1 = &ranlxd1_type;
- const gsl_rng_type *gsl_rng_ranlxd2 = &ranlxd2_type;
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