60 lines
1.5 KiB
V
60 lines
1.5 KiB
V
// Copyright (c) 2019-2022 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module wyrand
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import rand.seed
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import rand.constants
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import hash
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// Redefinition of some constants that we will need for pseudorandom number generation.
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const (
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wyp0 = u64(0xa0761d6478bd642f)
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wyp1 = u64(0xe7037ed1a0b428db)
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)
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// WyRandRNG is a RNG based on the WyHash hashing algorithm.
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pub struct WyRandRNG {
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mut:
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state u64 = seed.time_seed_64()
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has_extra bool
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extra u32
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}
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// seed sets the seed, needs only two `u32`s in little-endian format as [lower, higher].
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pub fn (mut rng WyRandRNG) seed(seed_data []u32) {
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if seed_data.len != 2 {
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eprintln('WyRandRNG needs 2 32-bit unsigned integers as the seed.')
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exit(1)
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}
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rng.state = seed_data[0] | (u64(seed_data[1]) << 32)
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rng.has_extra = false
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}
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// u32 updates the PRNG state and returns the next pseudorandom `u32`.
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[inline]
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pub fn (mut rng WyRandRNG) u32() u32 {
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if rng.has_extra {
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rng.has_extra = false
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return rng.extra
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}
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full_value := rng.u64()
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lower := u32(full_value & constants.lower_mask)
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upper := u32(full_value >> 32)
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rng.extra = upper
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rng.has_extra = true
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return lower
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}
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// u64 updates the PRNG state and returns the next pseudorandom `u64`.
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[inline]
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pub fn (mut rng WyRandRNG) u64() u64 {
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unsafe {
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mut seed1 := rng.state
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seed1 += wyrand.wyp0
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rng.state = seed1
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return hash.wymum(seed1 ^ wyrand.wyp1, seed1)
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}
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return 0
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}
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