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58 lines
1.6 KiB
V
58 lines
1.6 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 splitmix64
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import rand.seed
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import rand.constants
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// SplitMix64RNG ported from http://xoshiro.di.unimi.it/splitmix64.c
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pub struct SplitMix64RNG {
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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 of the accepting SplitMix64RNG to the given data
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// in little-endian format (i.e. lower 32 bits are in [0] and higher 32 bits in [1]).
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pub fn (mut rng SplitMix64RNG) seed(seed_data []u32) {
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if seed_data.len != 2 {
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eprintln('SplitMix64RNG 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 SplitMix64RNG) 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 SplitMix64RNG) u64() u64 {
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rng.state += (0x9e3779b97f4a7c15)
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mut z := rng.state
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z = (z ^ (z >> u64(30))) * 0xbf58476d1ce4e5b9
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z = (z ^ (z >> u64(27))) * 0x94d049bb133111eb
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return z ^ (z >> (31))
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}
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// free should be called when the generator is no longer needed
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[unsafe]
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pub fn (mut rng SplitMix64RNG) free() {
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unsafe { free(rng) }
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}
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