Class: Random

Inherits:
Object show all
Defined in:
random.c

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#new([seed]) ⇒ Object

Creates new Mersenne Twister based pseudorandom number generator with seed. When the argument seed is omitted, the generator is initialized with Random.new_seed.

The argument seed is used to ensure repeatable sequences of random numbers between different runs of the program.

prng = Random.new(1234)
[ prng.rand, prng.rand ]   #=> [0.191519450378892, 0.622108771039832]
[ prng.integer(10), prng.integer(1000) ]  #=> [4, 664]
prng = Random.new(1234)
[ prng.rand, prng.rand ]   #=> [0.191519450378892, 0.622108771039832]




# File 'random.c'

/*
 * call-seq: Random.new([seed]) -> prng
 *
 * Creates new Mersenne Twister based pseudorandom number generator with
 * seed.  When the argument seed is omitted, the generator is initialized
 * with Random.new_seed.
 *
 * The argument seed is used to ensure repeatable sequences of random numbers
 * between different runs of the program.
 *
 *     prng = Random.new(1234)
 *     [ prng.rand, prng.rand ]   #=> [0.191519450378892, 0.622108771039832]
 *     [ prng.integer(10), prng.integer(1000) ]  #=> [4, 664]
 *     prng = Random.new(1234)
 *     [ prng.rand, prng.rand ]   #=> [0.191519450378892, 0.622108771039832]
 */
static VALUE
random_init(int argc, VALUE *argv, VALUE obj)
{
    VALUE vseed;
    rb_random_t *rnd = get_rnd(obj);

    if (argc == 0) {
    vseed = random_seed();
    }
    else {
    rb_scan_args(argc, argv, "01", &vseed);
    }
    rnd->seed = rand_init(&rnd->mt, vseed);
    return obj;
}

Class Method Details

.new_seed ⇒ Integer

Returns arbitrary value for seed.

Returns:




# File 'random.c'

/*
 * call-seq: Random.new_seed -> integer
 *
 * Returns arbitrary value for seed.
 */
static VALUE
random_seed(void)
{
    unsigned int buf[DEFAULT_SEED_CNT];
    fill_random_seed(buf);
    return make_seed_value(buf);
}

.rand(max = 0) ⇒ Numeric

Converts max to an integer using max1 = max.to_i.abs. If max is nil the result is zero, returns a pseudorandom floating point number greater than or equal to 0.0 and less than 1.0. Otherwise, returns a pseudorandom integer greater than or equal to zero and less than max1. Kernel::srand may be used to ensure repeatable sequences of random numbers between different runs of the program. Ruby currently uses a modified Mersenne Twister with a period of 2**19937-1.

srand 1234                 #=> 0
[ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]
[ rand(10), rand(1000) ]   #=> [6, 817]
srand 1234                 #=> 1234
[ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]

Returns:




# File 'random.c'

/*
 *  call-seq:
 *     rand(max=0)    -> number
 *
 *  Converts <i>max</i> to an integer using max1 =
 *  max<code>.to_i.abs</code>. If _max_ is +nil+ the result is zero, returns a
 *  pseudorandom floating point number greater than or equal to 0.0 and
 *  less than 1.0. Otherwise, returns a pseudorandom integer greater
 *  than or equal to zero and less than max1. <code>Kernel::srand</code>
 *  may be used to ensure repeatable sequences of random numbers between
 *  different runs of the program. Ruby currently uses a modified
 *  Mersenne Twister with a period of 2**19937-1.
 *
 *     srand 1234                 #=> 0
 *     [ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]
 *     [ rand(10), rand(1000) ]   #=> [6, 817]
 *     srand 1234                 #=> 1234
 *     [ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]
 */

static VALUE
rb_f_rand(int argc, VALUE *argv, VALUE obj)
{
    VALUE vmax, r;
    struct MT *mt = default_mt();

    if (argc == 0) goto zero_arg;
    rb_scan_args(argc, argv, "01", &vmax);
    if (NIL_P(vmax)) goto zero_arg;
    vmax = rb_to_int(vmax);
    if (vmax == INT2FIX(0) || NIL_P(r = rand_int(mt, vmax, 0))) {
      zero_arg:
    return DBL2NUM(genrand_real(mt));
    }
    return r;
}

.srand(number = 0) ⇒ Object

Seeds the pseudorandom number generator to the value of number. If number is omitted or zero, seeds the generator using a combination of the time, the process id, and a sequence number. (This is also the behavior if Kernel::rand is called without previously calling srand, but without the sequence.) By setting the seed to a known value, scripts can be made deterministic during testing. The previous seed value is returned. Also see Kernel::rand.




# File 'random.c'

/*
 *  call-seq:
 *     srand(number=0)    -> old_seed
 *
 *  Seeds the pseudorandom number generator to the value of
 *  <i>number</i>. If <i>number</i> is omitted
 *  or zero, seeds the generator using a combination of the time, the
 *  process id, and a sequence number. (This is also the behavior if
 *  <code>Kernel::rand</code> is called without previously calling
 *  <code>srand</code>, but without the sequence.) By setting the seed
 *  to a known value, scripts can be made deterministic during testing.
 *  The previous seed value is returned. Also see <code>Kernel::rand</code>.
 */

static VALUE
rb_f_srand(int argc, VALUE *argv, VALUE obj)
{
    VALUE seed, old;
    rb_random_t *r = &default_rand;

    rb_secure(4);
    if (argc == 0) {
    seed = random_seed();
    }
    else {
    rb_scan_args(argc, argv, "01", &seed);
    }
    old = r->seed;
    r->seed = rand_init(&r->mt, seed);

    return old;
}

Instance Method Details

#==(prng2) ⇒ Boolean

Returns true if the generators' states equal.

Returns:

  • (Boolean) 



# File 'random.c'

/*
 * call-seq:
 *     prng1 == prng2 -> true or false
 *
 * Returns true if the generators' states equal.
 */
static VALUE
random_equal(VALUE self, VALUE other)
{
    rb_random_t *r1, *r2;
    if (rb_obj_class(self) != rb_obj_class(other)) return Qfalse;
    r1 = get_rnd(self);
    r2 = get_rnd(other);
    if (!RTEST(rb_funcall2(r1->seed, rb_intern("=="), 1, &r2->seed))) return Qfalse;
    if (memcmp(r1->mt.state, r2->mt.state, sizeof(r1->mt.state))) return Qfalse;
    if ((r1->mt.next - r1->mt.state) != (r2->mt.next - r2->mt.state)) return Qfalse;
    if (r1->mt.left != r2->mt.left) return Qfalse;
    return Qtrue;
}

#bytes(size) ⇒ Object

Returns a random binary string. The argument size specified the length of the result string.




# File 'random.c'

/*
 * call-seq: prng.bytes(size) -> prng
 *
 * Returns a random binary string.  The argument size specified the length of
 * the result string.
 */
static VALUE
random_bytes(VALUE obj, VALUE len)
{
    return rb_random_bytes(obj, NUM2LONG(rb_to_int(len)));
}

#initialize_copy ⇒ Object

:nodoc:




# File 'random.c'

/* :nodoc: */
static VALUE
random_copy(VALUE obj, VALUE orig)
{
    rb_random_t *rnd1 = get_rnd(obj);
    rb_random_t *rnd2 = get_rnd(orig);
    struct MT *mt = &rnd1->mt;

    *rnd1 = *rnd2;
    mt->next = mt->state + numberof(mt->state) - mt->left + 1;
    return obj;
}

#left ⇒ Object

:nodoc:




# File 'random.c'

/* :nodoc: */
static VALUE
random_left(VALUE obj)
{
    rb_random_t *rnd = get_rnd(obj);
    return INT2FIX(rnd->mt.left);
}

#marshal_dump ⇒ Object

:nodoc:




# File 'random.c'

/* :nodoc: */
static VALUE
random_dump(VALUE obj)
{
    rb_random_t *rnd = get_rnd(obj);
    VALUE dump = rb_ary_new2(3);

    rb_ary_push(dump, mt_state(&rnd->mt));
    rb_ary_push(dump, INT2FIX(rnd->mt.left));
    rb_ary_push(dump, rnd->seed);

    return dump;
}

#marshal_load ⇒ Object

:nodoc:




# File 'random.c'

/* :nodoc: */
static VALUE
random_load(VALUE obj, VALUE dump)
{
    rb_random_t *rnd = get_rnd(obj);
    struct MT *mt = &rnd->mt;
    VALUE state, left = INT2FIX(1), seed = INT2FIX(0);
    VALUE *ary;
    unsigned long x;

    Check_Type(dump, T_ARRAY);
    ary = RARRAY_PTR(dump);
    switch (RARRAY_LEN(dump)) {
      case 3:
    seed = ary[2];
      case 2:
    left = ary[1];
      case 1:
    state = ary[0];
    break;
      default:
    rb_raise(rb_eArgError, "wrong dump data");
    }
    memset(mt->state, 0, sizeof(mt->state));
    if (FIXNUM_P(state)) {
    x = FIX2ULONG(state);
    mt->state[0] = (unsigned int)x;
#if SIZEOF_LONG / SIZEOF_INT >= 2
    mt->state[1] = (unsigned int)(x >> BITSPERDIG);
#endif
#if SIZEOF_LONG / SIZEOF_INT >= 3
    mt->state[2] = (unsigned int)(x >> 2 * BITSPERDIG);
#endif
#if SIZEOF_LONG / SIZEOF_INT >= 4
    mt->state[3] = (unsigned int)(x >> 3 * BITSPERDIG);
#endif
    }
    else {
    BDIGIT *d;
    long len;
    Check_Type(state, T_BIGNUM);
    len = RBIGNUM_LEN(state);
    if (len > roomof(sizeof(mt->state), SIZEOF_BDIGITS)) {
        len = roomof(sizeof(mt->state), SIZEOF_BDIGITS);
    }
#if SIZEOF_BDIGITS < SIZEOF_INT
    else if (len % DIGSPERINT) {
        d = RBIGNUM_DIGITS(state) + len;
# if DIGSPERINT == 2
        --len;
        x = *--d;
# else
        x = 0;
        do {
        x = (x << BITSPERDIG) | *--d;
        } while (--len % DIGSPERINT);
# endif
        mt->state[len / DIGSPERINT] = (unsigned int)x;
    }
#endif
    if (len > 0) {
        d = BDIGITS(state) + len;
        do {
        --len;
        x = *--d;
# if DIGSPERINT == 2
        --len;
        x = (x << BITSPERDIG) | *--d;
# elif SIZEOF_BDIGITS < SIZEOF_INT
        do {
            x = (x << BITSPERDIG) | *--d;
        } while (--len % DIGSPERINT);
# endif
        mt->state[len / DIGSPERINT] = (unsigned int)x;
        } while (len > 0);
    }
    }
    x = NUM2ULONG(left);
    if (x > numberof(mt->state)) {
    rb_raise(rb_eArgError, "wrong value");
    }
    mt->left = (unsigned int)x;
    mt->next = mt->state + numberof(mt->state) - x + 1;
    rnd->seed = rb_to_int(seed);

    return obj;
}

#rand ⇒ Float #rand(limit) ⇒ Numeric

When the argument is an Integer or a Bignum, it returns a random integer greater than or equal to zero and less than the argument. Unlike Random.rand, when the argument is a negative integer or zero, it raises an ArgumentError.

When the argument is a Float, it returns a random floating point number between 0.0 and max, including 0.0 and excluding max.

When the argument limit is a Range, it returns a random number where range.member?(number) == true.

prng.rand(5..9)  #=> one of [5, 6, 7, 8, 9]
prng.rand(5...9) #=> one of [5, 6, 7, 8]
prng.rand(5.0..9.0) #=> between 5.0 and 9.0, including 9.0
prng.rand(5.0...9.0) #=> between 5.0 and 9.0, excluding 9.0

begin/end of the range have to have subtract and add methods.

Otherwise, it raises an ArgumentError.

Overloads:




# File 'random.c'

/*
 * call-seq:
 *     prng.rand -> float
 *     prng.rand(limit) -> number
 *
 * When the argument is an +Integer+ or a +Bignum+, it returns a
 * random integer greater than or equal to zero and less than the
 * argument.  Unlike Random.rand, when the argument is a negative
 * integer or zero, it raises an ArgumentError.
 *
 * When the argument is a +Float+, it returns a random floating point
 * number between 0.0 and _max_, including 0.0 and excluding _max_.
 *
 * When the argument _limit_ is a +Range+, it returns a random
 * number where range.member?(number) == true.
 *     prng.rand(5..9)  #=> one of [5, 6, 7, 8, 9]
 *     prng.rand(5...9) #=> one of [5, 6, 7, 8]
 *     prng.rand(5.0..9.0) #=> between 5.0 and 9.0, including 9.0
 *     prng.rand(5.0...9.0) #=> between 5.0 and 9.0, excluding 9.0
 *
 * +begin+/+end+ of the range have to have subtract and add methods.
 *
 * Otherwise, it raises an ArgumentError.
 */
static VALUE
random_rand(int argc, VALUE *argv, VALUE obj)
{
    rb_random_t *rnd = get_rnd(obj);
    VALUE vmax, beg = Qundef, v;
    int excl = 0;

    if (argc == 0) {
    return rb_float_new(genrand_real(&rnd->mt));
    }
    else if (argc != 1) {
    rb_raise(rb_eArgError, "wrong number of arguments (%d for 0..1)", argc);
    }
    vmax = argv[0];
    if (NIL_P(vmax)) {
    v = Qnil;
    }
    else if (TYPE(vmax) != T_FLOAT && (v = rb_check_to_integer(vmax, "to_int"), !NIL_P(v))) {
    v = rand_int(&rnd->mt, vmax = v, 1);
    }
    else if (v = rb_check_to_float(vmax), !NIL_P(v)) {
    double max = float_value(v);
    if (max > 0.0)
        v = rb_float_new(max * genrand_real(&rnd->mt));
    else
        v = Qnil;
    }
    else if ((v = range_values(vmax, &beg, &excl)) != Qfalse) {
    vmax = v;
    if (TYPE(vmax) != T_FLOAT && (v = rb_check_to_integer(vmax, "to_int"), !NIL_P(v))) {
        long max;
        vmax = v;
        v = Qnil;
        if (FIXNUM_P(vmax)) {
          fixnum:
        if ((max = FIX2LONG(vmax) - excl) >= 0) {
            unsigned long r = limited_rand(&rnd->mt, (unsigned long)max);
            v = ULONG2NUM(r);
        }
        }
        else if (BUILTIN_TYPE(vmax) == T_BIGNUM && RBIGNUM_SIGN(vmax) && !rb_bigzero_p(vmax)) {
        vmax = excl ? rb_big_minus(vmax, INT2FIX(1)) : rb_big_norm(vmax);
        if (FIXNUM_P(vmax)) {
            excl = 0;
            goto fixnum;
        }
        v = limited_big_rand(&rnd->mt, RBIGNUM(vmax));
        }
    }
    else if (v = rb_check_to_float(vmax), !NIL_P(v)) {
        double max = float_value(v), r;
        v = Qnil;
        if (max > 0.0) {
        if (excl) {
            r = genrand_real(&rnd->mt);
        }
        else {
            r = genrand_real2(&rnd->mt);
        }
        v = rb_float_new(r * max);
        }
        else if (max == 0.0 && !excl) {
        v = rb_float_new(0.0);
        }
    }
    }
    else {
    v = Qnil;
    NUM2LONG(vmax);
    }
    if (NIL_P(v)) {
    VALUE mesg = rb_str_new_cstr("invalid argument - ");
    rb_str_append(mesg, rb_obj_as_string(argv[0]));
    rb_exc_raise(rb_exc_new3(rb_eArgError, mesg));
    }
    if (beg == Qundef) return v;
    if (FIXNUM_P(beg) && FIXNUM_P(v)) {
    long x = FIX2LONG(beg) + FIX2LONG(v);
    return LONG2NUM(x);
    }
    switch (TYPE(v)) {
      case T_BIGNUM:
    return rb_big_plus(v, beg);
      case T_FLOAT: {
    VALUE f = rb_check_to_float(beg);
    if (!NIL_P(f)) {
        RFLOAT_VALUE(v) += RFLOAT_VALUE(f);
        return v;
    }
      }
      default:
    return rb_funcall2(beg, id_plus, 1, &v);
    }
}

#seed ⇒ Integer

Returns the seed of the generator.

Returns:




# File 'random.c'

/*
 * call-seq: prng.seed -> integer
 *
 * Returns the seed of the generator.
 */
static VALUE
random_get_seed(VALUE obj)
{
    return get_rnd(obj)->seed;
}

#state ⇒ Object

:nodoc:




# File 'random.c'

/* :nodoc: */
static VALUE
random_state(VALUE obj)
{
    rb_random_t *rnd = get_rnd(obj);
    return mt_state(&rnd->mt);
}