Initial project import

tools/v/vlib/rand/splitmix64/splitmix64.v

@@ -0,0 +1,96 @@
+// Copyright (c) 2019-2024 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.buffer
+
+pub const seed_len = 2
+
+// SplitMix64RNG is ported from http://xoshiro.di.unimi.it/splitmix64.c .
+pub struct SplitMix64RNG {
+	buffer.PRNGBuffer
+mut:
+	state      u64 = seed.time_seed_64()
+	bytes_left int
+	buffer     u64
+}
+
+// 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.bytes_left = 0
+	rng.buffer = 0
+}
+
+// byte returns a uniformly distributed pseudorandom 8-bit unsigned positive `byte`.
+@[inline]
+pub fn (mut rng SplitMix64RNG) u8() u8 {
+	if rng.bytes_left >= 1 {
+		rng.bytes_left -= 1
+		value := u8(rng.buffer)
+		rng.buffer >>= 8
+		return value
+	}
+	rng.buffer = rng.u64()
+	rng.bytes_left = 7
+	value := u8(rng.buffer)
+	rng.buffer >>= 8
+	return value
+}
+
+// u16 returns a pseudorandom 16bit int in range `[0, 2¹⁶)`.
+@[inline]
+pub fn (mut rng SplitMix64RNG) u16() u16 {
+	if rng.bytes_left >= 2 {
+		rng.bytes_left -= 2
+		value := u16(rng.buffer)
+		rng.buffer >>= 16
+		return value
+	}
+	ans := rng.u64()
+	rng.buffer = ans >> 16
+	rng.bytes_left = 6
+	return u16(ans)
+}
+
+// u32 returns a pseudorandom 32bit int in range `[0, 2³²)`.
+@[inline]
+pub fn (mut rng SplitMix64RNG) u32() u32 {
+	if rng.bytes_left >= 4 {
+		rng.bytes_left -= 4
+		value := u32(rng.buffer)
+		rng.buffer >>= 32
+		return value
+	}
+	ans := rng.u64()
+	rng.buffer = ans >> 32
+	rng.bytes_left = 4
+	return u32(ans)
+}
+
+// u64 returns a pseudorandom 64bit int in range `[0, 2⁶⁴)`.
+@[ignore_overflow; 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))
+}
+
+// block_size returns the number of bits that the RNG can produce in a single iteration.
+@[inline]
+pub fn (mut rng SplitMix64RNG) block_size() int {
+	return 64
+}
+
+// free should be called when the generator is no longer needed.
+@[unsafe]
+pub fn (mut rng SplitMix64RNG) free() {
+}

tools/v/vlib/rand/splitmix64/splitmix64_test.v

@@ -0,0 +1,317 @@
+import math
+import rand
+import rand.splitmix64
+import rand.seed
+
+const range_limit = 40
+const value_count = 1000
+const seeds = [[u32(42), 0], [u32(256), 0]]
+
+const sample_size = 1000
+const stats_epsilon = 0.05
+const inv_sqrt_12 = 1.0 / math.sqrt(12)
+
+fn gen_randoms(seed_data []u32, bound int) []u64 {
+	bound_u64 := u64(bound)
+	mut randoms := []u64{len: (20)}
+	mut rnd := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+	rnd.seed(seed_data)
+	for i in 0 .. 20 {
+		randoms[i] = rnd.u64n(bound_u64) or { panic("Couldn't obtain u64") }
+	}
+	return randoms
+}
+
+fn test_splitmix64_reproducibility() {
+	seed_data := seed.time_seed_array(2)
+	randoms1 := gen_randoms(seed_data, 1000)
+	randoms2 := gen_randoms(seed_data, 1000)
+	assert randoms1.len == randoms2.len
+	len := randoms1.len
+	for i in 0 .. len {
+		assert randoms1[i] == randoms2[i]
+	}
+}
+
+fn test_splitmix64_variability() {
+	// If this test fails and if it is certainly not the implementation
+	// at fault, try changing the seed values. Repeated values are
+	// improbable but not impossible.
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		mut values := []u64{cap: value_count}
+		for i in 0 .. value_count {
+			value := rng.u64()
+			assert value !in values
+			assert values.len == i
+			values << value
+		}
+	}
+}
+
+fn check_uniformity_u64(mut rng rand.PRNG, range u64) {
+	range_f64 := f64(range)
+	expected_mean := range_f64 / 2.0
+	mut variance := 0.0
+	for _ in 0 .. sample_size {
+		diff := f64(rng.u64n(range) or { panic("Couldn't obtain u64") }) - expected_mean
+		variance += diff * diff
+	}
+	variance /= sample_size - 1
+	sigma := math.sqrt(variance)
+	expected_sigma := range_f64 * inv_sqrt_12
+	error := (sigma - expected_sigma) / expected_sigma
+	assert math.abs(error) < stats_epsilon
+}
+
+fn test_splitmix64_uniformity_u64() {
+	ranges := [14019545, 80240, 130]
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for range in ranges {
+			check_uniformity_u64(mut rng, u64(range))
+		}
+	}
+}
+
+fn check_uniformity_f64(mut rng rand.PRNG) {
+	expected_mean := 0.5
+	mut variance := 0.0
+	for _ in 0 .. sample_size {
+		diff := rng.f64() - expected_mean
+		variance += diff * diff
+	}
+	variance /= sample_size - 1
+	sigma := math.sqrt(variance)
+	expected_sigma := inv_sqrt_12
+	error := (sigma - expected_sigma) / expected_sigma
+	assert math.abs(error) < stats_epsilon
+}
+
+fn test_splitmix64_uniformity_f64() {
+	// The f64 version
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		check_uniformity_f64(mut rng)
+	}
+}
+
+fn test_splitmix64_u32n() {
+	max := u32(16384)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.u32n(max) or { panic("Couldn't obtain u32") }
+			assert value >= 0
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_u64n() {
+	max := u64(379091181005)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.u64n(max) or { panic("Couldn't obtain u64") }
+			assert value >= 0
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_u32_in_range() {
+	max := u32(484468466)
+	min := u32(316846)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.u32_in_range(min, max) or { panic("Couldn't obtain u32 in range") }
+			assert value >= min
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_u64_in_range() {
+	max := u64(216468454685163)
+	min := u64(6848646868)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.u64_in_range(min, max) or { panic("Couldn't obtain u64 in range") }
+			assert value >= min
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_int31() {
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(u32(0x80000000))
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.int31()
+			assert value >= 0
+			assert value <= max_u31
+			// This statement ensures that the sign bit is zero
+			assert (value & sign_mask) == 0
+		}
+	}
+}
+
+fn test_splitmix64_int63() {
+	max_u63 := i64(0x7FFFFFFFFFFFFFFF)
+	sign_mask := i64(u64(0x8000000000000000))
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.int63()
+			assert value >= 0
+			assert value <= max_u63
+			assert (value & sign_mask) == 0
+		}
+	}
+}
+
+fn test_splitmix64_intn() {
+	max := 2525642
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.intn(max) or { panic("Couldn't obtain int") }
+			assert value >= 0
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_i64n() {
+	max := i64(3246727724653636)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.i64n(max) or { panic("Couldn't obtain i64") }
+			assert value >= 0
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_int_in_range() {
+	min := -4252
+	max := 230549862
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.int_in_range(min, max) or { panic("Couldn't obtain int in range") }
+			assert value >= min
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_i64_in_range() {
+	min := i64(-24095)
+	max := i64(324058)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.i64_in_range(min, max) or { panic("Couldn't obtain i64 in range") }
+			assert value >= min
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_f32() {
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.f32()
+			assert value >= 0.0
+			assert value < 1.0
+		}
+	}
+}
+
+fn test_splitmix64_f64() {
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.f64()
+			assert value >= 0.0
+			assert value < 1.0
+		}
+	}
+}
+
+fn test_splitmix64_f32n() {
+	max := f32(357.0)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.f32n(max) or { panic("Couldn't obtain f32") }
+			assert value >= 0.0
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_f64n() {
+	max := 1.52e6
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.f64n(max) or { panic("Couldn't obtain f64") }
+			assert value >= 0.0
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_f32_in_range() {
+	min := f32(-24.0)
+	max := f32(125.0)
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.f32_in_range(min, max) or { panic("Couldn't obtain f32 in range") }
+			assert value >= min
+			assert value < max
+		}
+	}
+}
+
+fn test_splitmix64_f64_in_range() {
+	min := -548.7
+	max := 5015.2
+	for seed in seeds {
+		mut rng := &rand.PRNG(&splitmix64.SplitMix64RNG{})
+		rng.seed(seed)
+		for _ in 0 .. range_limit {
+			value := rng.f64_in_range(min, max) or { panic("Couldn't obtain f64 in range") }
+			assert value >= min
+			assert value < max
+		}
+	}
+}