/* Authors: O. Teytaud

 * Copyright (C) 2007  O. Teytaud 

 * (all comments welcome at olivier.teytaud@inria.fr)

 *

 * 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.

 */

/* Implementation for Halton generator.  See [J.H. Halton, On the

 * efficiency of certain quasi-random sequences of points in

 * evaluating multi-dimensional integrals Numerische Mathematik, 1960]

 */

#include <config.h>

#include <gsl/gsl_qrng.h>

/* maximum allowed space dimension */

#define HALTON_MAX_DIMENSION 1229

/* prototypes for generator type functions */

static size_t halton_state_size (unsigned int dimension);

static int halton_init (void *state, unsigned int dimension);

static int halton_get (void *state, unsigned int dimension, double *v);

/* global Halton generator type object */

static const gsl_qrng_type halton_type = {

  "halton",

  HALTON_MAX_DIMENSION,

  halton_state_size,

  halton_init,

  halton_get

};

const gsl_qrng_type *gsl_qrng_halton = &halton_type;

/* prime numbers (thanks to trolltech http://doc.trolltech.com/3.2/primes.html)

*/

static const int prime_numbers[HALTON_MAX_DIMENSION] = {

  2, 3, 5, 7, 11, 13, 17, 19, 23, 29,

  31, 37, 41, 43, 47, 53, 59, 61, 67, 71,

  73, 79, 83, 89, 97, 101, 103, 107, 109, 113,

  127, 131, 137, 139, 149, 151, 157, 163, 167, 173,

  179, 181, 191, 193, 197, 199, 211, 223, 227, 229,

  233, 239, 241, 251, 257, 263, 269, 271, 277, 281,

  283, 293, 307, 311, 313, 317, 331, 337, 347, 349,

  353, 359, 367, 373, 379, 383, 389, 397, 401, 409,

  419, 421, 431, 433, 439, 443, 449, 457, 461, 463,

  467, 479, 487, 491, 499, 503, 509, 521, 523, 541,

  547, 557, 563, 569, 571, 577, 587, 593, 599, 601,

  607, 613, 617, 619, 631, 641, 643, 647, 653, 659,

  661, 673, 677, 683, 691, 701, 709, 719, 727, 733,

  739, 743, 751, 757, 761, 769, 773, 787, 797, 809,

  811, 821, 823, 827, 829, 839, 853, 857, 859, 863,

  877, 881, 883, 887, 907, 911, 919, 929, 937, 941,

  947, 953, 967, 971, 977, 983, 991, 997, 1009, 1013,

  1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069,

  1087, 1091, 1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151,

  1153, 1163, 1171, 1181, 1187, 1193, 1201, 1213, 1217, 1223,

  1229, 1231, 1237, 1249, 1259, 1277, 1279, 1283, 1289, 1291,

  1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361, 1367, 1373,

  1381, 1399, 1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451,

  1453, 1459, 1471, 1481, 1483, 1487, 1489, 1493, 1499, 1511,

  1523, 1531, 1543, 1549, 1553, 1559, 1567, 1571, 1579, 1583,

  1597, 1601, 1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657,

  1663, 1667, 1669, 1693, 1697, 1699, 1709, 1721, 1723, 1733,

  1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789, 1801, 1811,

  1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877, 1879, 1889,

  1901, 1907, 1913, 1931, 1933, 1949, 1951, 1973, 1979, 1987,

  1993, 1997, 1999, 2003, 2011, 2017, 2027, 2029, 2039, 2053,

  2063, 2069, 2081, 2083, 2087, 2089, 2099, 2111, 2113, 2129,

  2131, 2137, 2141, 2143, 2153, 2161, 2179, 2203, 2207, 2213,

  2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273, 2281, 2287,

  2293, 2297, 2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357,

  2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411, 2417, 2423,

  2437, 2441, 2447, 2459, 2467, 2473, 2477, 2503, 2521, 2531,

  2539, 2543, 2549, 2551, 2557, 2579, 2591, 2593, 2609, 2617,

  2621, 2633, 2647, 2657, 2659, 2663, 2671, 2677, 2683, 2687,

  2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729, 2731, 2741,

  2749, 2753, 2767, 2777, 2789, 2791, 2797, 2801, 2803, 2819,

  2833, 2837, 2843, 2851, 2857, 2861, 2879, 2887, 2897, 2903,

  2909, 2917, 2927, 2939, 2953, 2957, 2963, 2969, 2971, 2999,

  3001, 3011, 3019, 3023, 3037, 3041, 3049, 3061, 3067, 3079,

  3083, 3089, 3109, 3119, 3121, 3137, 3163, 3167, 3169, 3181,

  3187, 3191, 3203, 3209, 3217, 3221, 3229, 3251, 3253, 3257,

  3259, 3271, 3299, 3301, 3307, 3313, 3319, 3323, 3329, 3331,

  3343, 3347, 3359, 3361, 3371, 3373, 3389, 3391, 3407, 3413,

  3433, 3449, 3457, 3461, 3463, 3467, 3469, 3491, 3499, 3511,

  3517, 3527, 3529, 3533, 3539, 3541, 3547, 3557, 3559, 3571,

  3581, 3583, 3593, 3607, 3613, 3617, 3623, 3631, 3637, 3643,

  3659, 3671, 3673, 3677, 3691, 3697, 3701, 3709, 3719, 3727,

  3733, 3739, 3761, 3767, 3769, 3779, 3793, 3797, 3803, 3821,

  3823, 3833, 3847, 3851, 3853, 3863, 3877, 3881, 3889, 3907,

  3911, 3917, 3919, 3923, 3929, 3931, 3943, 3947, 3967, 3989,

  4001, 4003, 4007, 4013, 4019, 4021, 4027, 4049, 4051, 4057,

  4073, 4079, 4091, 4093, 4099, 4111, 4127, 4129, 4133, 4139,

  4153, 4157, 4159, 4177, 4201, 4211, 4217, 4219, 4229, 4231,

  4241, 4243, 4253, 4259, 4261, 4271, 4273, 4283, 4289, 4297,

  4327, 4337, 4339, 4349, 4357, 4363, 4373, 4391, 4397, 4409,

  4421, 4423, 4441, 4447, 4451, 4457, 4463, 4481, 4483, 4493,

  4507, 4513, 4517, 4519, 4523, 4547, 4549, 4561, 4567, 4583,

  4591, 4597, 4603, 4621, 4637, 4639, 4643, 4649, 4651, 4657,

  4663, 4673, 4679, 4691, 4703, 4721, 4723, 4729, 4733, 4751,

  4759, 4783, 4787, 4789, 4793, 4799, 4801, 4813, 4817, 4831,

  4861, 4871, 4877, 4889, 4903, 4909, 4919, 4931, 4933, 4937,

  4943, 4951, 4957, 4967, 4969, 4973, 4987, 4993, 4999, 5003,

  5009, 5011, 5021, 5023, 5039, 5051, 5059, 5077, 5081, 5087,

  5099, 5101, 5107, 5113, 5119, 5147, 5153, 5167, 5171, 5179,

  5189, 5197, 5209, 5227, 5231, 5233, 5237, 5261, 5273, 5279,

  5281, 5297, 5303, 5309, 5323, 5333, 5347, 5351, 5381, 5387,

  5393, 5399, 5407, 5413, 5417, 5419, 5431, 5437, 5441, 5443,

  5449, 5471, 5477, 5479, 5483, 5501, 5503, 5507, 5519, 5521,

  5527, 5531, 5557, 5563, 5569, 5573, 5581, 5591, 5623, 5639,

  5641, 5647, 5651, 5653, 5657, 5659, 5669, 5683, 5689, 5693,

  5701, 5711, 5717, 5737, 5741, 5743, 5749, 5779, 5783, 5791,

  5801, 5807, 5813, 5821, 5827, 5839, 5843, 5849, 5851, 5857,

  5861, 5867, 5869, 5879, 5881, 5897, 5903, 5923, 5927, 5939,

  5953, 5981, 5987, 6007, 6011, 6029, 6037, 6043, 6047, 6053,

  6067, 6073, 6079, 6089, 6091, 6101, 6113, 6121, 6131, 6133,

  6143, 6151, 6163, 6173, 6197, 6199, 6203, 6211, 6217, 6221,

  6229, 6247, 6257, 6263, 6269, 6271, 6277, 6287, 6299, 6301,

  6311, 6317, 6323, 6329, 6337, 6343, 6353, 6359, 6361, 6367,

  6373, 6379, 6389, 6397, 6421, 6427, 6449, 6451, 6469, 6473,

  6481, 6491, 6521, 6529, 6547, 6551, 6553, 6563, 6569, 6571,

  6577, 6581, 6599, 6607, 6619, 6637, 6653, 6659, 6661, 6673,

  6679, 6689, 6691, 6701, 6703, 6709, 6719, 6733, 6737, 6761,

  6763, 6779, 6781, 6791, 6793, 6803, 6823, 6827, 6829, 6833,

  6841, 6857, 6863, 6869, 6871, 6883, 6899, 6907, 6911, 6917,

  6947, 6949, 6959, 6961, 6967, 6971, 6977, 6983, 6991, 6997,

  7001, 7013, 7019, 7027, 7039, 7043, 7057, 7069, 7079, 7103,

  7109, 7121, 7127, 7129, 7151, 7159, 7177, 7187, 7193, 7207,

  7211, 7213, 7219, 7229, 7237, 7243, 7247, 7253, 7283, 7297,

  7307, 7309, 7321, 7331, 7333, 7349, 7351, 7369, 7393, 7411,

  7417, 7433, 7451, 7457, 7459, 7477, 7481, 7487, 7489, 7499,

  7507, 7517, 7523, 7529, 7537, 7541, 7547, 7549, 7559, 7561,

  7573, 7577, 7583, 7589, 7591, 7603, 7607, 7621, 7639, 7643,

  7649, 7669, 7673, 7681, 7687, 7691, 7699, 7703, 7717, 7723,

  7727, 7741, 7753, 7757, 7759, 7789, 7793, 7817, 7823, 7829,

  7841, 7853, 7867, 7873, 7877, 7879, 7883, 7901, 7907, 7919,

  7927, 7933, 7937, 7949, 7951, 7963, 7993, 8009, 8011, 8017,

  8039, 8053, 8059, 8069, 8081, 8087, 8089, 8093, 8101, 8111,

  8117, 8123, 8147, 8161, 8167, 8171, 8179, 8191, 8209, 8219,

  8221, 8231, 8233, 8237, 8243, 8263, 8269, 8273, 8287, 8291,

  8293, 8297, 8311, 8317, 8329, 8353, 8363, 8369, 8377, 8387,

  8389, 8419, 8423, 8429, 8431, 8443, 8447, 8461, 8467, 8501,

  8513, 8521, 8527, 8537, 8539, 8543, 8563, 8573, 8581, 8597,

  8599, 8609, 8623, 8627, 8629, 8641, 8647, 8663, 8669, 8677,

  8681, 8689, 8693, 8699, 8707, 8713, 8719, 8731, 8737, 8741,

  8747, 8753, 8761, 8779, 8783, 8803, 8807, 8819, 8821, 8831,

  8837, 8839, 8849, 8861, 8863, 8867, 8887, 8893, 8923, 8929,

  8933, 8941, 8951, 8963, 8969, 8971, 8999, 9001, 9007, 9011,

  9013, 9029, 9041, 9043, 9049, 9059, 9067, 9091, 9103, 9109,

  9127, 9133, 9137, 9151, 9157, 9161, 9173, 9181, 9187, 9199,

  9203, 9209, 9221, 9227, 9239, 9241, 9257, 9277, 9281, 9283,

  9293, 9311, 9319, 9323, 9337, 9341, 9343, 9349, 9371, 9377,

  9391, 9397, 9403, 9413, 9419, 9421, 9431, 9433, 9437, 9439,

  9461, 9463, 9467, 9473, 9479, 9491, 9497, 9511, 9521, 9533,

  9539, 9547, 9551, 9587, 9601, 9613, 9619, 9623, 9629, 9631,

  9643, 9649, 9661, 9677, 9679, 9689, 9697, 9719, 9721, 9733,

  9739, 9743, 9749, 9767, 9769, 9781, 9787, 9791, 9803, 9811,

  9817, 9829, 9833, 9839, 9851, 9857, 9859, 9871, 9883, 9887,

  9901, 9907, 9923, 9929, 9931, 9941, 9949, 9967, 9973

};

/* Halton generator state.

 *   sequence_count       = number of calls with this generator

 */

typedef struct

{

  unsigned int sequence_count;

} 

halton_state_t;

static size_t

halton_state_size (unsigned int dimension)

{

  return sizeof (halton_state_t);

}

static int

halton_init (void *state, unsigned int dimension)

{

  halton_state_t *h_state = (halton_state_t *) state;

  h_state->sequence_count = 0;

  if (dimension < 1 || dimension > HALTON_MAX_DIMENSION)

    {

      return GSL_EINVAL;

    }

  return GSL_SUCCESS;

}

static double

vdcorput (int x, int b)

{

  double r = 0.;

  double v = 1.;

  double binv = 1. / (double) b;

  while (x > 0)

    {

      v *= binv;

      r += v * (double) (x % b);

      x /= b;

    }

  return r;

}

static int

halton_get (void *state, unsigned int dimension, double *v)

{

  halton_state_t *h_state = (halton_state_t *) state;

  unsigned int i;

  if (dimension < 1 || dimension > HALTON_MAX_DIMENSION)

    {

      return GSL_EINVAL;

    }

  h_state->sequence_count++;

  for (i = 0; i < dimension; i++)

    {

      v[i] = vdcorput (h_state->sequence_count, prime_numbers[i]);

    }

  return GSL_SUCCESS;

}