gsl_cbrng.h

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/*
Copyright 2010-2011, D. E. Shaw Research.
All rights reserved.

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modification, are permitted provided that the following conditions are
met:

* Redistributions of source code must retain the above copyright
  notice, this list of conditions, and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions, and the following disclaimer in the
  documentation and/or other materials provided with the distribution.

* Neither the name of D. E. Shaw Research nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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*/
#ifndef __r123_compat_gslrng_dot_h__
#define __r123_compat_gslrng_dot_h__

#include <gsl/gsl_rng.h>
#include <string.h>

#define GSL_CBRNG(NAME, CBRNGNAME)                                      \
const gsl_rng_type *gsl_rng_##NAME;                                     \
                                                                        \
typedef struct{                                                         \
    CBRNGNAME##_ctr_t ctr;                                                   \
    CBRNGNAME##_ctr_t r;                                                     \
    CBRNGNAME##_key_t key;                                                   \
    int elem;                                                           \
} NAME##_state;                                                         \
                                                                        \
static unsigned long int NAME##_get(void *vstate){                      \
    NAME##_state *st = (NAME##_state *)vstate;                          \
    const int N=sizeof(st->ctr.v)/sizeof(st->ctr.v[0]);                 \
    if( st->elem == 0 ){                                                \
        ++st->ctr.v[0];                                                 \
        if( N>1 && st->ctr.v[0] == 0 ) ++st->ctr.v[1];                  \
        if( N>2 && st->ctr.v[1] == 0 ) ++st->ctr.v[2];                  \
        if( N>3 && st->ctr.v[2] == 0 ) ++st->ctr.v[3];                  \
        st->r = CBRNGNAME(st->ctr, st->key);                                 \
        st->elem = N;                                                   \
    }                                                                   \
    return 0xffffffffUL & st->r.v[--st->elem];                          \
}                                                                       \
                                                                        \
static double                                                           \
NAME##_get_double (void * vstate)                                       \
{                                                                       \
    return NAME##_get (vstate)/4294967296.0;                            \
}                                                                       \
                                                                        \
static void NAME##_set(void *vstate, unsigned long int s){              \
    NAME##_state *st = (NAME##_state *)vstate;                          \
    st->elem = 0;                                                       \
    /* Assume that key and ctr have an array member, v,                 \
       as if they are r123arrayNxW.  If not, this will fail             \
       to compile.  In particular, this macro fails to compile          \
       when the underlying CBRNG requires use of keyinit */             \
    memset(&st->ctr.v[0], 0, sizeof(st->ctr.v));                        \
    memset(&st->key.v[0], 0, sizeof(st->key.v));                        \
    /* GSL 1.15 documentation says this about gsl_rng_set:              \
         Note that the most generators only accept 32-bit seeds, with higher \
         values being reduced modulo 2^32.  For generators with smaller \
         ranges the maximum seed value will typically be lower.         \
     so we won't jump through any hoops here to deal with               \
     high bits if sizeof(unsigned long) > sizeof(uint32_t). */          \
    st->key.v[0] = s;                                                   \
}                                                                       \
                                                                        \
static const gsl_rng_type NAME##_type = {                               \
    #NAME,                                                              \
    0xffffffffUL,                                                       \
    0,                                                                  \
    sizeof(NAME##_state),                                               \
    &NAME##_set,                                                        \
    &NAME##_get,                                                        \
    &NAME##_get_double                                                  \
};                                                                      \
                                                                        \
const gsl_rng_type *gsl_rng_##NAME = &NAME##_type

#endif