path: root/rand.c

/* Copyright 2010-2015
 * Kaz Kylheku <kaz@kylheku.com>
 * Vancouver, Canada
 * All rights reserved.
 *
 * Redistribution of this software in source and binary forms, with or without
 * modification, is permitted provided that the following two conditions are met.
 *
 * Use of this software in any manner constitutes agreement with the disclaimer
 * which follows the two conditions.
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DAMAGES, HOWEVER CAUSED,
 * AND UNDER ANY THEORY OF LIABILITY, ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wctype.h>
#include <limits.h>
#include <stdarg.h>
#include <dirent.h>
#include <setjmp.h>
#include <wchar.h>
#include <limits.h>
#include <time.h>
#include <signal.h>
#include "config.h"
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "lib.h"
#include "signal.h"
#include "unwind.h"
#include "arith.h"
#include "rand.h"
#include "eval.h"

#if SIZEOF_INT == 4
typedef unsigned int rand32_t;
#elif SIZEOF_LONG == 4
typedef unsigned long rand32_t;
#endif

/*
 * The algorithm here is WELL 512.
 * (Francois Panneton, Pierre L'Ecuyer.)
 */
struct rand_state {
  rand32_t state[16];
  unsigned cur;
};

val random_state_s;

static struct cobj_ops random_state_ops = cobj_ops_init(eq,
                                                        cobj_print_op,
                                                        cobj_destroy_free_op,
                                                        cobj_mark_op,
                                                        cobj_hash_op);

static val make_state(void)
{
  struct rand_state *r = coerce(struct rand_state *, chk_malloc(sizeof *r));
  return cobj(coerce(mem_t *, r), random_state_s, &random_state_ops);
}

val random_state_p(val obj)
{
  return typeof(obj) == random_state_s ? t : nil;
}

INLINE rand32_t *rstate(struct rand_state *r, int offs)
{
  return &r->state[(r->cur + offs) % 16];
}

static rand32_t rand32(struct rand_state *r)
{
  rand32_t s0 = *rstate(r, 0);
  rand32_t s9 = *rstate(r, 9);
  rand32_t s13 = *rstate(r, 13);
  rand32_t s15 = *rstate(r, 15);

  rand32_t r1 = s0 ^ (s0 << 16) ^ s13 ^ (s13 << 15);
  rand32_t r2 = s9 ^ (s9 >> 11);

  rand32_t ns0 = *rstate(r, 0) = r1 ^ r2;
  rand32_t ns15 = s15 ^ (s15 << 2) ^ r1 ^ (r1 << 18) ^ r2 ^ (r2 << 28) ^
                  ((ns0 ^ (ns0 << 5)) & 0xda442d24ul);

  *rstate(r, 15) = ns15;
  r->cur = (r->cur + 15) % 16;
  return ns15;
}

val make_random_state(val seed)
{
  val rs = make_state();
  int i, copy = 0;
  struct rand_state *r = coerce(struct rand_state *,
                                cobj_handle(rs, random_state_s));

  seed = default_bool_arg(seed);

  if (bignump(seed)) {
    int i, dig, bit;
    mp_int *m = mp(seed);

    for (i = 0, dig = 0, bit = 0; i < 16 && dig < m->used; i++) {
      r->state[i] = (m->dp[dig] >> bit) & 0xFFFFFFFFul;
      bit += 32;
      if (bit >= MP_DIGIT_BIT)
        dig++, bit = 0;
    }

    while (i > 0 && !r->state[i - 1])
      i--;

    if (i < 16)
      memset(r->state + i, 0xAA, sizeof r->state - i * sizeof r->state[0]);
  } else if (fixnump(seed)) {
    cnum s = c_num(seed) & NUM_MAX;

    memset(r->state, 0xAA, sizeof r->state);
    r->state[0] = s & 0xFFFFFFFFul;
#if SIZEOF_PTR >= 8
    s >>= 32;
    if (s)
      r->state[1] = s & 0xFFFFFFFFul;
#endif
#if SIZEOF_PTR >= 16
    s >>= 32;
    if (s)
      r->state[2] = s & 0xFFFFFFFFul;
#endif
  } else if (nilp(seed)) {
    val time = time_sec_usec();
    r->state[0] = convert(rand32_t, c_num(car(time)));
    r->state[1] = convert(rand32_t, c_num(cdr(time)));
    r->state[2] = convert(rand32_t, getpid());
    memset(r->state + 3, 0xAA, sizeof r->state - 3 * sizeof r->state[0]);
  } else if (random_state_p(seed)) {
    struct rand_state *rseed = coerce(struct rand_state *,
                                      cobj_handle(seed, random_state_s));
    *r = *rseed;
    copy = 1;
  } else {
    uw_throwf(error_s, lit("make-random-state: seed ~s is not a number"),
              seed, nao);
  }

  if (!copy) {
    r->cur = 0;
    for (i = 0; i < 8; i++)
      (void) rand32(r);
  }

  return rs;
}

val random_fixnum(val state)
{
  struct rand_state *r = coerce(struct rand_state *,
                                cobj_handle(default_arg(state, random_state),
                                            random_state_s));
  return num(rand32(r) & NUM_MAX);
}

val random(val state, val modulus)
{
  struct rand_state *r = coerce(struct rand_state *,
                                cobj_handle(state, random_state_s));

  if (bignump(modulus)) {
    mp_int *m = mp(modulus);
    int bits = mp_count_bits(m);
    int rands_needed = (bits + 32 - 1) / 32;
    int msb_rand_bits = bits % 32;
    rand32_t msb_rand_mask = convert(rand32_t, -1) >> (32 - msb_rand_bits);
    val out = make_bignum();
    mp_int *om = mp(out);

    for (;;) {
      int i;
      for (i = 0; i < rands_needed; i++) {
        rand32_t rnd = rand32(r);
#if MP_DIGIT_SIZE >= 4
        if (i > 0)
          mp_mul_2d(om, 32, om);
        else
          rnd &= msb_rand_mask;
        mp_add_d(om, rnd, om);
#else
        if (i > 0)
          mp_mul_2d(om, 16, om);
        else
          rnd &= msb_rand_mask;
        mp_add_d(om, rnd & 0xFFFF, om);
        mp_mul_2d(om, 16, om);
        mp_add_d(om, rnd >> 16, om);
#endif
      }
      if (mp_cmp(om, m) != MP_LT) {
        mp_zero(om);
        continue;
      }
      break;
    }

    return normalize(out);
  } else if (fixnump(modulus)) {
    cnum m = c_num(modulus);
    int bits = highest_bit(m);
#if SIZEOF_PTR >= 8
    int rands_needed = (bits + 32 - 1) / 32;
#endif
    int msb_rand_bits = bits % 32;
    rand32_t msb_rand_mask = convert(rand32_t, -1) >> (32 - msb_rand_bits);
    if (m <= 0)
      goto invalid;
    for (;;) {
      cnum out = 0;
#if SIZEOF_PTR >= 8
      int i;

      for (i = 0; i < rands_needed; i++) {
        rand32_t rnd = rand32(r);
        out <<= 32;
        if (i == 0)
          rnd &= msb_rand_mask;
        out |= rnd;
      }
#else
      out = rand32(r) & msb_rand_mask;
#endif
      if (out >= m)
        continue;
      return num(out);
    }
  }
invalid:
  uw_throwf(numeric_error_s, lit("random: invalid modulus ~s"),
      modulus, nao);
}

val rnd(val modulus, val state)
{
  state = default_arg(state, random_state);
  return random(state, modulus);
}

void rand_init(void)
{
  random_state_s = intern(lit("*random-state*"), user_package);
  reg_var(random_state_s, make_random_state(num_fast(42)));
}