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+/* rng/ranlxs.c
+ *
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 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 2 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 & 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 (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;
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