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// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module splitmix64
import rand.seed
import rand.constants
// SplitMix64RNG ported from http://xoshiro.di.unimi.it/splitmix64.c
pub struct SplitMix64RNG {
mut:
state u64 = seed.time_seed_64()
has_extra bool
extra u32
}
// seed sets the seed of the accepting SplitMix64RNG to the given data
// in little-endian format (i.e. lower 32 bits are in [0] and higher 32 bits in [1]).
pub fn (mut rng SplitMix64RNG) seed(seed_data []u32) {
if seed_data.len != 2 {
eprintln('SplitMix64RNG needs 2 32-bit unsigned integers as the seed.')
exit(1)
}
rng.state = seed_data[0] | (u64(seed_data[1]) << 32)
rng.has_extra = false
}
// u32 updates the PRNG state and returns the next pseudorandom `u32`.
[inline]
pub fn (mut rng SplitMix64RNG) u32() u32 {
if rng.has_extra {
rng.has_extra = false
return rng.extra
}
full_value := rng.u64()
lower := u32(full_value & constants.lower_mask)
upper := u32(full_value >> 32)
rng.extra = upper
rng.has_extra = true
return lower
}
// u64 updates the PRNG state and returns the next pseudorandom `u64`.
[inline]
pub fn (mut rng SplitMix64RNG) u64() u64 {
rng.state += (0x9e3779b97f4a7c15)
mut z := rng.state
z = (z ^ ((z >> u64(30)))) * (0xbf58476d1ce4e5b9)
z = (z ^ ((z >> u64(27)))) * (0x94d049bb133111eb)
return z ^ (z >> (31))
}
// u32n returns a pseudorandom `u32` less than `bound`.
[inline]
pub fn (mut rng SplitMix64RNG) u32n(bound u32) u32 {
// This function is kept similar to the u64 version
if bound == 0 {
eprintln('max must be non-zero')
exit(1)
}
threshold := -bound % bound
for {
r := rng.u32()
if r >= threshold {
return r % bound
}
}
return u32(0)
}
// u64n returns a pseudorandom `u64` less than `bound`.
[inline]
pub fn (mut rng SplitMix64RNG) u64n(bound u64) u64 {
// See pcg32.v for explanation of comment. This algorithm
// existed before the refactoring.
if bound == 0 {
eprintln('max must be non-zero')
exit(1)
}
threshold := -bound % bound
for {
r := rng.u64()
if r >= threshold {
return r % bound
}
}
return u64(0)
}
// u32n returns a pseudorandom `u32` value that is guaranteed to be in range `[min, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) u32_in_range(min u32, max u32) u32 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + rng.u32n(max - min)
}
// u64n returns a pseudorandom `u64` value that is guaranteed to be in range `[min, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) u64_in_range(min u64, max u64) u64 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + rng.u64n(max - min)
}
// int returns a pseudorandom 32-bit (possibly negative) `int`.
[inline]
pub fn (mut rng SplitMix64RNG) int() int {
return int(rng.u32())
}
// i64 returns a pseudorandom 64-bit (possibly negative) `i64`.
[inline]
pub fn (mut rng SplitMix64RNG) i64() i64 {
return i64(rng.u64())
}
// int31 returns a positive pseudorandom 31-bit `int`.
[inline]
pub fn (mut rng SplitMix64RNG) int31() int {
return int(rng.u32() & constants.u31_mask) // Set the 32nd bit to 0.
}
// int63 returns a positive pseudorandom 63-bit `i64`.
[inline]
pub fn (mut rng SplitMix64RNG) int63() i64 {
return i64(rng.u64() & constants.u63_mask) // Set the 64th bit to 0.
}
// intn returns a pseudorandom `int` in range `[0, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) intn(max int) int {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return int(rng.u32n(u32(max)))
}
// i64n returns a pseudorandom `i64` in range `[0, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) i64n(max i64) i64 {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return i64(rng.u64n(u64(max)))
}
// int_in_range returns a pseudorandom `int` in range `[min, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) int_in_range(min int, max int) int {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
// This supports negative ranges like [-10, -5) because the difference is positive
return min + rng.intn(max - min)
}
// i64_in_range returns a pseudorandom `i64` in range `[min, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) i64_in_range(min i64, max i64) i64 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + rng.i64n(max - min)
}
// f32 returns a pseudorandom `f32` value in range `[0, 1)`.
[inline]
pub fn (mut rng SplitMix64RNG) f32() f32 {
return f32(rng.u32()) / constants.max_u32_as_f32
}
// f64 returns a pseudorandom `f64` value in range `[0, 1)`.
[inline]
pub fn (mut rng SplitMix64RNG) f64() f64 {
return f64(rng.u64()) / constants.max_u64_as_f64
}
// f32n returns a pseudorandom `f32` value in range `[0, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) f32n(max f32) f32 {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return rng.f32() * max
}
// f64n returns a pseudorandom `f64` value in range `[0, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) f64n(max f64) f64 {
if max <= 0 {
eprintln('max has to be positive.')
exit(1)
}
return rng.f64() * max
}
// f32_in_range returns a pseudorandom `f32` in range `[min, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) f32_in_range(min f32, max f32) f32 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + rng.f32n(max - min)
}
// i64_in_range returns a pseudorandom `i64` in range `[min, max)`.
[inline]
pub fn (mut rng SplitMix64RNG) f64_in_range(min f64, max f64) f64 {
if max <= min {
eprintln('max must be greater than min')
exit(1)
}
return min + rng.f64n(max - min)
}
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