ref: ac7fed3ddfa3caf2e2c97f221e023b75ec9693ac
dir: /libstd/rand.myr/
use "die.use"
use "types.use"
use "alloc.use"
/*
Translated from C by Ori Bernstein
*/
/*
A C-program for MT19937, with initialization improved 2002/1/26.
Coded by Takuji Nishimura and Makoto Matsumoto.
Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
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.
3. The names of its contributors may not 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
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Any feedback is very welcome.
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
*/
pkg std =
type rng
const mksrng : (seed : uint32 -> rng#)
const delrng : (rng : rng# -> void)
generic rand : (rng : rng#, lo : @a::(numeric,integral), hi : @a::(numeric,integral) -> @a::(numeric,integral))
generic randN : (rng : rng# -> @a::(numeric,integral))
const randbytes : (rng : rng#, buf : byte[:] -> size)
const rand32 : (rng : rng# -> uint32)
;;
type rng = struct
state : uint32[624]
i : uint32
;;
/* allocates and initializes a random number generator */
const mksrng = {seed
var rng
rng = alloc()
init(rng, seed)
-> rng
}
const delrng = {rng
free(rng)
}
/* initializes a random number generator from the seed `seed`. */
const init = {rng, seed
var i
for i = 0; i < 624; i++
rng.state[i] = seed
seed = 1812433253 * (seed ^ (seed >> 30)) + i + 1
;;
rng.i = i
}
/*
Generates a random integer from `rng` in the range [lo, hi),
returning the value. The range [lo, hi) must be positive,
nonempty, and the difference between hi and lo must be
less then 2^(type_bits - 1)
*/
generic rand = {rng, lo, hi -> @a::(integral,numeric)
var span, lim
var maxrand
var val
assert(hi - lo > 0, "rand.myr: range for random values must be >= 1")
span = hi - lo
maxrand = (1 << (8*sizeof(@a))) - 1 /* max for signed value */
if maxrand < 0 /* signed */
maxrand = (1 << (8*sizeof(@a)-1)) - 1 /* max for signed value */
;;
lim = (maxrand/span)*span
val = (randN(rng) & maxrand)
while val > lim
val = (randN(rng) & maxrand)
;;
-> val % span + lo
}
/*
Generates a random integer of any size from the
random number generator `rng`. The returned value
may be negative, if the type is signed.
*/
generic randN = {rng -> @a::(integral,numeric)
var i, val
val = 0
for i = 0; i < sizeof(@a)/4; i++
val <<= 8*sizeof(@a)
val |= rand32(rng) castto(@a::(integral,numeric))
;;
-> val
}
/*
generates a 32 bit unsigned random number
from the random number generator `rng`.
*/
const rand32 = {rng
var x
if rng.i == 624
next(rng)
;;
x = rng.state[rng.i]
rng.i++
x ^= x >> 11
x ^= (x << 7) & 0x9D2C5680
x ^= (x << 15) & 0xEFC60000
-> x ^ (x >> 18)
}
const randbytes = {rng, buf
var i, n, r
n = 0
for i = 0; i < buf.len/4; i++
r = rand32(rng)
buf[n++] = (r >> 0 & 0xff) castto(byte)
buf[n++] = (r >> 8 & 0xff) castto(byte)
buf[n++] = (r >> 16 & 0xff) castto(byte)
buf[n++] = (r >> 32 & 0xff) castto(byte)
;;
r = rand32(rng)
for ; n != buf.len; n++
buf[n++] = (r & 0xff) castto(byte)
r >>= 8
;;
-> n
}
/* updates random number generator state when we tick over. */
const next = {rng
var k
var y
for k = 0; k < 227; k++
y = (rng.state[k] & 0x80000000) | (rng.state[k + 1] & 0x7FFFFFFF)
rng.state[k] = rng.state[k + 397] ^ (y >> 1) ^ ((y & 1) * 0x9908B0DF)
;;
for ; k < 623; k++
y = (rng.state[k] & 0x80000000) | (rng.state[k + 1] & 0x7FFFFFFF)
rng.state[k] = rng.state[k - 227] ^ (y >> 1) ^ ((y & 1) * 0x9908B0DF);
;;
y = (rng.state[623] & 0x80000000) | (rng.state[0] & 0x7FFFFFFF)
rng.state[623] = rng.state[396] ^ (y >> 1) ^ ((y & 1) * 0x9908B0DF);
rng.i = 0
}