// 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) }