mirror of
https://github.com/ziglang/zig.git
synced 2024-11-30 17:12:31 +00:00
1106 lines
33 KiB
Zig
1106 lines
33 KiB
Zig
// The engines provided here should be initialized from an external source. For now, randomBytes
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// from the crypto package is the most suitable. Be sure to use a CSPRNG when required, otherwise using
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// a normal PRNG will be faster and use substantially less stack space.
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//
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// ```
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// var buf: [8]u8 = undefined;
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// try std.crypto.randomBytes(buf[0..]);
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// const seed = mem.readIntSliceLittle(u64, buf[0..8]);
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//
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// var r = DefaultPrng.init(seed);
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//
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// const s = r.random.int(u64);
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// ```
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//
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// TODO(tiehuis): Benchmark these against other reference implementations.
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const std = @import("std.zig");
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const builtin = @import("builtin");
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const assert = std.debug.assert;
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const expect = std.testing.expect;
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const expectEqual = std.testing.expectEqual;
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const mem = std.mem;
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const math = std.math;
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const ziggurat = @import("rand/ziggurat.zig");
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const maxInt = std.math.maxInt;
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// When you need fast unbiased random numbers
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pub const DefaultPrng = Xoroshiro128;
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// When you need cryptographically secure random numbers
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pub const DefaultCsprng = Isaac64;
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pub const Random = struct {
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fillFn: fn (r: *Random, buf: []u8) void,
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/// Read random bytes into the specified buffer until full.
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pub fn bytes(r: *Random, buf: []u8) void {
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r.fillFn(r, buf);
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}
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pub fn boolean(r: *Random) bool {
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return r.int(u1) != 0;
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}
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/// Returns a random int `i` such that `0 <= i <= maxInt(T)`.
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/// `i` is evenly distributed.
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pub fn int(r: *Random, comptime T: type) T {
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const UnsignedT = @IntType(false, T.bit_count);
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const ByteAlignedT = @IntType(false, @divTrunc(T.bit_count + 7, 8) * 8);
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var rand_bytes: [@sizeOf(ByteAlignedT)]u8 = undefined;
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r.bytes(rand_bytes[0..]);
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// use LE instead of native endian for better portability maybe?
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// TODO: endian portability is pointless if the underlying prng isn't endian portable.
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// TODO: document the endian portability of this library.
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const byte_aligned_result = mem.readIntSliceLittle(ByteAlignedT, rand_bytes);
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const unsigned_result = @truncate(UnsignedT, byte_aligned_result);
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return @bitCast(T, unsigned_result);
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}
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/// Constant-time implementation off ::uintLessThan.
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/// The results of this function may be biased.
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pub fn uintLessThanBiased(r: *Random, comptime T: type, less_than: T) T {
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comptime assert(T.is_signed == false);
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comptime assert(T.bit_count <= 64); // TODO: workaround: LLVM ERROR: Unsupported library call operation!
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assert(0 < less_than);
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if (T.bit_count <= 32) {
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return @intCast(T, limitRangeBiased(u32, r.int(u32), less_than));
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} else {
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return @intCast(T, limitRangeBiased(u64, r.int(u64), less_than));
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}
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}
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/// Returns an evenly distributed random unsigned integer `0 <= i < less_than`.
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/// This function assumes that the underlying ::fillFn produces evenly distributed values.
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/// Within this assumption, the runtime of this function is exponentially distributed.
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/// If ::fillFn were backed by a true random generator,
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/// the runtime of this function would technically be unbounded.
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/// However, if ::fillFn is backed by any evenly distributed pseudo random number generator,
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/// this function is guaranteed to return.
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/// If you need deterministic runtime bounds, use `::uintLessThanBiased`.
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pub fn uintLessThan(r: *Random, comptime T: type, less_than: T) T {
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comptime assert(T.is_signed == false);
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comptime assert(T.bit_count <= 64); // TODO: workaround: LLVM ERROR: Unsupported library call operation!
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assert(0 < less_than);
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// Small is typically u32
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const Small = @IntType(false, @divTrunc(T.bit_count + 31, 32) * 32);
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// Large is typically u64
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const Large = @IntType(false, Small.bit_count * 2);
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// adapted from:
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// http://www.pcg-random.org/posts/bounded-rands.html
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// "Lemire's (with an extra tweak from me)"
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var x: Small = r.int(Small);
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var m: Large = Large(x) * Large(less_than);
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var l: Small = @truncate(Small, m);
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if (l < less_than) {
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// TODO: workaround for https://github.com/ziglang/zig/issues/1770
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// should be:
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// var t: Small = -%less_than;
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var t: Small = @bitCast(Small, -%@bitCast(@IntType(true, Small.bit_count), Small(less_than)));
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if (t >= less_than) {
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t -= less_than;
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if (t >= less_than) {
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t %= less_than;
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}
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}
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while (l < t) {
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x = r.int(Small);
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m = Large(x) * Large(less_than);
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l = @truncate(Small, m);
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}
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}
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return @intCast(T, m >> Small.bit_count);
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}
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/// Constant-time implementation off ::uintAtMost.
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/// The results of this function may be biased.
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pub fn uintAtMostBiased(r: *Random, comptime T: type, at_most: T) T {
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assert(T.is_signed == false);
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if (at_most == maxInt(T)) {
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// have the full range
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return r.int(T);
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}
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return r.uintLessThanBiased(T, at_most + 1);
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}
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/// Returns an evenly distributed random unsigned integer `0 <= i <= at_most`.
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/// See ::uintLessThan, which this function uses in most cases,
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/// for commentary on the runtime of this function.
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pub fn uintAtMost(r: *Random, comptime T: type, at_most: T) T {
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assert(T.is_signed == false);
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if (at_most == maxInt(T)) {
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// have the full range
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return r.int(T);
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}
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return r.uintLessThan(T, at_most + 1);
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}
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/// Constant-time implementation off ::intRangeLessThan.
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/// The results of this function may be biased.
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pub fn intRangeLessThanBiased(r: *Random, comptime T: type, at_least: T, less_than: T) T {
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assert(at_least < less_than);
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if (T.is_signed) {
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// Two's complement makes this math pretty easy.
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const UnsignedT = @IntType(false, T.bit_count);
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const lo = @bitCast(UnsignedT, at_least);
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const hi = @bitCast(UnsignedT, less_than);
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const result = lo +% r.uintLessThanBiased(UnsignedT, hi -% lo);
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return @bitCast(T, result);
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} else {
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// The signed implementation would work fine, but we can use stricter arithmetic operators here.
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return at_least + r.uintLessThanBiased(T, less_than - at_least);
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}
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}
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/// Returns an evenly distributed random integer `at_least <= i < less_than`.
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/// See ::uintLessThan, which this function uses in most cases,
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/// for commentary on the runtime of this function.
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pub fn intRangeLessThan(r: *Random, comptime T: type, at_least: T, less_than: T) T {
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assert(at_least < less_than);
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if (T.is_signed) {
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// Two's complement makes this math pretty easy.
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const UnsignedT = @IntType(false, T.bit_count);
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const lo = @bitCast(UnsignedT, at_least);
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const hi = @bitCast(UnsignedT, less_than);
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const result = lo +% r.uintLessThan(UnsignedT, hi -% lo);
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return @bitCast(T, result);
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} else {
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// The signed implementation would work fine, but we can use stricter arithmetic operators here.
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return at_least + r.uintLessThan(T, less_than - at_least);
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}
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}
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/// Constant-time implementation off ::intRangeAtMostBiased.
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/// The results of this function may be biased.
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pub fn intRangeAtMostBiased(r: *Random, comptime T: type, at_least: T, at_most: T) T {
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assert(at_least <= at_most);
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if (T.is_signed) {
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// Two's complement makes this math pretty easy.
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const UnsignedT = @IntType(false, T.bit_count);
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const lo = @bitCast(UnsignedT, at_least);
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const hi = @bitCast(UnsignedT, at_most);
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const result = lo +% r.uintAtMostBiased(UnsignedT, hi -% lo);
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return @bitCast(T, result);
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} else {
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// The signed implementation would work fine, but we can use stricter arithmetic operators here.
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return at_least + r.uintAtMostBiased(T, at_most - at_least);
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}
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}
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/// Returns an evenly distributed random integer `at_least <= i <= at_most`.
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/// See ::uintLessThan, which this function uses in most cases,
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/// for commentary on the runtime of this function.
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pub fn intRangeAtMost(r: *Random, comptime T: type, at_least: T, at_most: T) T {
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assert(at_least <= at_most);
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if (T.is_signed) {
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// Two's complement makes this math pretty easy.
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const UnsignedT = @IntType(false, T.bit_count);
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const lo = @bitCast(UnsignedT, at_least);
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const hi = @bitCast(UnsignedT, at_most);
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const result = lo +% r.uintAtMost(UnsignedT, hi -% lo);
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return @bitCast(T, result);
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} else {
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// The signed implementation would work fine, but we can use stricter arithmetic operators here.
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return at_least + r.uintAtMost(T, at_most - at_least);
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}
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}
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/// TODO: deprecated. use ::boolean or ::int instead.
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pub fn scalar(r: *Random, comptime T: type) T {
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return if (T == bool) r.boolean() else r.int(T);
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}
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/// TODO: deprecated. renamed to ::intRangeLessThan
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pub fn range(r: *Random, comptime T: type, start: T, end: T) T {
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return r.intRangeLessThan(T, start, end);
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}
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/// Return a floating point value evenly distributed in the range [0, 1).
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pub fn float(r: *Random, comptime T: type) T {
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// Generate a uniform value between [1, 2) and scale down to [0, 1).
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// Note: The lowest mantissa bit is always set to 0 so we only use half the available range.
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switch (T) {
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f32 => {
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const s = r.int(u32);
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const repr = (0x7f << 23) | (s >> 9);
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return @bitCast(f32, repr) - 1.0;
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},
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f64 => {
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const s = r.int(u64);
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const repr = (0x3ff << 52) | (s >> 12);
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return @bitCast(f64, repr) - 1.0;
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},
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else => @compileError("unknown floating point type"),
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}
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}
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/// Return a floating point value normally distributed with mean = 0, stddev = 1.
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///
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/// To use different parameters, use: floatNorm(...) * desiredStddev + desiredMean.
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pub fn floatNorm(r: *Random, comptime T: type) T {
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const value = ziggurat.next_f64(r, ziggurat.NormDist);
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switch (T) {
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f32 => return @floatCast(f32, value),
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f64 => return value,
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else => @compileError("unknown floating point type"),
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}
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}
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/// Return an exponentially distributed float with a rate parameter of 1.
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///
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/// To use a different rate parameter, use: floatExp(...) / desiredRate.
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pub fn floatExp(r: *Random, comptime T: type) T {
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const value = ziggurat.next_f64(r, ziggurat.ExpDist);
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switch (T) {
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f32 => return @floatCast(f32, value),
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f64 => return value,
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else => @compileError("unknown floating point type"),
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}
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}
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/// Shuffle a slice into a random order.
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pub fn shuffle(r: *Random, comptime T: type, buf: []T) void {
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if (buf.len < 2) {
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return;
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}
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var i: usize = 0;
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while (i < buf.len - 1) : (i += 1) {
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const j = r.intRangeLessThan(usize, i, buf.len);
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mem.swap(T, &buf[i], &buf[j]);
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}
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}
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};
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/// Convert a random integer 0 <= random_int <= maxValue(T),
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/// into an integer 0 <= result < less_than.
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/// This function introduces a minor bias.
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pub fn limitRangeBiased(comptime T: type, random_int: T, less_than: T) T {
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comptime assert(T.is_signed == false);
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const T2 = @IntType(false, T.bit_count * 2);
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// adapted from:
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// http://www.pcg-random.org/posts/bounded-rands.html
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// "Integer Multiplication (Biased)"
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var m: T2 = T2(random_int) * T2(less_than);
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return @intCast(T, m >> T.bit_count);
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}
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const SequentialPrng = struct {
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const Self = @This();
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random: Random,
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next_value: u8,
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pub fn init() Self {
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return Self{
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.random = Random{ .fillFn = fill },
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.next_value = 0,
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};
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}
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fn fill(r: *Random, buf: []u8) void {
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const self = @fieldParentPtr(Self, "random", r);
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for (buf) |*b| {
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b.* = self.next_value;
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}
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self.next_value +%= 1;
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}
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};
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test "Random int" {
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testRandomInt();
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comptime testRandomInt();
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}
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fn testRandomInt() void {
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var r = SequentialPrng.init();
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expect(r.random.int(u0) == 0);
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r.next_value = 0;
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expect(r.random.int(u1) == 0);
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expect(r.random.int(u1) == 1);
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expect(r.random.int(u2) == 2);
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expect(r.random.int(u2) == 3);
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expect(r.random.int(u2) == 0);
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r.next_value = 0xff;
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expect(r.random.int(u8) == 0xff);
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r.next_value = 0x11;
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expect(r.random.int(u8) == 0x11);
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r.next_value = 0xff;
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expect(r.random.int(u32) == 0xffffffff);
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r.next_value = 0x11;
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expect(r.random.int(u32) == 0x11111111);
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r.next_value = 0xff;
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expect(r.random.int(i32) == -1);
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r.next_value = 0x11;
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expect(r.random.int(i32) == 0x11111111);
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r.next_value = 0xff;
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expect(r.random.int(i8) == -1);
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r.next_value = 0x11;
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expect(r.random.int(i8) == 0x11);
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r.next_value = 0xff;
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expect(r.random.int(u33) == 0x1ffffffff);
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r.next_value = 0xff;
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expect(r.random.int(i1) == -1);
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r.next_value = 0xff;
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expect(r.random.int(i2) == -1);
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r.next_value = 0xff;
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expect(r.random.int(i33) == -1);
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}
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test "Random boolean" {
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testRandomBoolean();
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comptime testRandomBoolean();
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}
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fn testRandomBoolean() void {
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var r = SequentialPrng.init();
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expect(r.random.boolean() == false);
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expect(r.random.boolean() == true);
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expect(r.random.boolean() == false);
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expect(r.random.boolean() == true);
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}
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test "Random intLessThan" {
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@setEvalBranchQuota(10000);
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testRandomIntLessThan();
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comptime testRandomIntLessThan();
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}
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fn testRandomIntLessThan() void {
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var r = SequentialPrng.init();
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r.next_value = 0xff;
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expect(r.random.uintLessThan(u8, 4) == 3);
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expect(r.next_value == 0);
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expect(r.random.uintLessThan(u8, 4) == 0);
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expect(r.next_value == 1);
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r.next_value = 0;
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expect(r.random.uintLessThan(u64, 32) == 0);
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// trigger the bias rejection code path
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r.next_value = 0;
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expect(r.random.uintLessThan(u8, 3) == 0);
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// verify we incremented twice
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expect(r.next_value == 2);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(u8, 0, 0x80) == 0x7f);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(u8, 0x7f, 0xff) == 0xfe);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(i8, 0, 0x40) == 0x3f);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(i8, -0x40, 0x40) == 0x3f);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(i8, -0x80, 0) == -1);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(i3, -4, 0) == -1);
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r.next_value = 0xff;
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expect(r.random.intRangeLessThan(i3, -2, 2) == 1);
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}
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test "Random intAtMost" {
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@setEvalBranchQuota(10000);
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testRandomIntAtMost();
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comptime testRandomIntAtMost();
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}
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fn testRandomIntAtMost() void {
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var r = SequentialPrng.init();
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r.next_value = 0xff;
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expect(r.random.uintAtMost(u8, 3) == 3);
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expect(r.next_value == 0);
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expect(r.random.uintAtMost(u8, 3) == 0);
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// trigger the bias rejection code path
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r.next_value = 0;
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expect(r.random.uintAtMost(u8, 2) == 0);
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// verify we incremented twice
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expect(r.next_value == 2);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(u8, 0, 0x7f) == 0x7f);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(u8, 0x7f, 0xfe) == 0xfe);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(i8, 0, 0x3f) == 0x3f);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(i8, -0x40, 0x3f) == 0x3f);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(i8, -0x80, -1) == -1);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(i3, -4, -1) == -1);
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r.next_value = 0xff;
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expect(r.random.intRangeAtMost(i3, -2, 1) == 1);
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expect(r.random.uintAtMost(u0, 0) == 0);
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}
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test "Random Biased" {
|
|
var r = DefaultPrng.init(0);
|
|
// Not thoroughly checking the logic here.
|
|
// Just want to execute all the paths with different types.
|
|
|
|
expect(r.random.uintLessThanBiased(u1, 1) == 0);
|
|
expect(r.random.uintLessThanBiased(u32, 10) < 10);
|
|
expect(r.random.uintLessThanBiased(u64, 20) < 20);
|
|
|
|
expect(r.random.uintAtMostBiased(u0, 0) == 0);
|
|
expect(r.random.uintAtMostBiased(u1, 0) <= 0);
|
|
expect(r.random.uintAtMostBiased(u32, 10) <= 10);
|
|
expect(r.random.uintAtMostBiased(u64, 20) <= 20);
|
|
|
|
expect(r.random.intRangeLessThanBiased(u1, 0, 1) == 0);
|
|
expect(r.random.intRangeLessThanBiased(i1, -1, 0) == -1);
|
|
expect(r.random.intRangeLessThanBiased(u32, 10, 20) >= 10);
|
|
expect(r.random.intRangeLessThanBiased(i32, 10, 20) >= 10);
|
|
expect(r.random.intRangeLessThanBiased(u64, 20, 40) >= 20);
|
|
expect(r.random.intRangeLessThanBiased(i64, 20, 40) >= 20);
|
|
|
|
// uncomment for broken module error:
|
|
//expect(r.random.intRangeAtMostBiased(u0, 0, 0) == 0);
|
|
expect(r.random.intRangeAtMostBiased(u1, 0, 1) >= 0);
|
|
expect(r.random.intRangeAtMostBiased(i1, -1, 0) >= -1);
|
|
expect(r.random.intRangeAtMostBiased(u32, 10, 20) >= 10);
|
|
expect(r.random.intRangeAtMostBiased(i32, 10, 20) >= 10);
|
|
expect(r.random.intRangeAtMostBiased(u64, 20, 40) >= 20);
|
|
expect(r.random.intRangeAtMostBiased(i64, 20, 40) >= 20);
|
|
}
|
|
|
|
// Generator to extend 64-bit seed values into longer sequences.
|
|
//
|
|
// The number of cycles is thus limited to 64-bits regardless of the engine, but this
|
|
// is still plenty for practical purposes.
|
|
const SplitMix64 = struct {
|
|
s: u64,
|
|
|
|
pub fn init(seed: u64) SplitMix64 {
|
|
return SplitMix64{ .s = seed };
|
|
}
|
|
|
|
pub fn next(self: *SplitMix64) u64 {
|
|
self.s +%= 0x9e3779b97f4a7c15;
|
|
|
|
var z = self.s;
|
|
z = (z ^ (z >> 30)) *% 0xbf58476d1ce4e5b9;
|
|
z = (z ^ (z >> 27)) *% 0x94d049bb133111eb;
|
|
return z ^ (z >> 31);
|
|
}
|
|
};
|
|
|
|
test "splitmix64 sequence" {
|
|
var r = SplitMix64.init(0xaeecf86f7878dd75);
|
|
|
|
const seq = [_]u64{
|
|
0x5dbd39db0178eb44,
|
|
0xa9900fb66b397da3,
|
|
0x5c1a28b1aeebcf5c,
|
|
0x64a963238f776912,
|
|
0xc6d4177b21d1c0ab,
|
|
0xb2cbdbdb5ea35394,
|
|
};
|
|
|
|
for (seq) |s| {
|
|
expect(s == r.next());
|
|
}
|
|
}
|
|
|
|
// PCG32 - http://www.pcg-random.org/
|
|
//
|
|
// PRNG
|
|
pub const Pcg = struct {
|
|
const default_multiplier = 6364136223846793005;
|
|
|
|
random: Random,
|
|
|
|
s: u64,
|
|
i: u64,
|
|
|
|
pub fn init(init_s: u64) Pcg {
|
|
var pcg = Pcg{
|
|
.random = Random{ .fillFn = fill },
|
|
.s = undefined,
|
|
.i = undefined,
|
|
};
|
|
|
|
pcg.seed(init_s);
|
|
return pcg;
|
|
}
|
|
|
|
fn next(self: *Pcg) u32 {
|
|
const l = self.s;
|
|
self.s = l *% default_multiplier +% (self.i | 1);
|
|
|
|
const xor_s = @truncate(u32, ((l >> 18) ^ l) >> 27);
|
|
const rot = @intCast(u32, l >> 59);
|
|
|
|
return (xor_s >> @intCast(u5, rot)) | (xor_s << @intCast(u5, (0 -% rot) & 31));
|
|
}
|
|
|
|
fn seed(self: *Pcg, init_s: u64) void {
|
|
// Pcg requires 128-bits of seed.
|
|
var gen = SplitMix64.init(init_s);
|
|
self.seedTwo(gen.next(), gen.next());
|
|
}
|
|
|
|
fn seedTwo(self: *Pcg, init_s: u64, init_i: u64) void {
|
|
self.s = 0;
|
|
self.i = (init_s << 1) | 1;
|
|
self.s = self.s *% default_multiplier +% self.i;
|
|
self.s +%= init_i;
|
|
self.s = self.s *% default_multiplier +% self.i;
|
|
}
|
|
|
|
fn fill(r: *Random, buf: []u8) void {
|
|
const self = @fieldParentPtr(Pcg, "random", r);
|
|
|
|
var i: usize = 0;
|
|
const aligned_len = buf.len - (buf.len & 7);
|
|
|
|
// Complete 4 byte segments.
|
|
while (i < aligned_len) : (i += 4) {
|
|
var n = self.next();
|
|
comptime var j: usize = 0;
|
|
inline while (j < 4) : (j += 1) {
|
|
buf[i + j] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
|
|
// Remaining. (cuts the stream)
|
|
if (i != buf.len) {
|
|
var n = self.next();
|
|
while (i < buf.len) : (i += 1) {
|
|
buf[i] = @truncate(u8, n);
|
|
n >>= 4;
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
test "pcg sequence" {
|
|
var r = Pcg.init(0);
|
|
const s0: u64 = 0x9394bf54ce5d79de;
|
|
const s1: u64 = 0x84e9c579ef59bbf7;
|
|
r.seedTwo(s0, s1);
|
|
|
|
const seq = [_]u32{
|
|
2881561918,
|
|
3063928540,
|
|
1199791034,
|
|
2487695858,
|
|
1479648952,
|
|
3247963454,
|
|
};
|
|
|
|
for (seq) |s| {
|
|
expect(s == r.next());
|
|
}
|
|
}
|
|
|
|
// Xoroshiro128+ - http://xoroshiro.di.unimi.it/
|
|
//
|
|
// PRNG
|
|
pub const Xoroshiro128 = struct {
|
|
random: Random,
|
|
|
|
s: [2]u64,
|
|
|
|
pub fn init(init_s: u64) Xoroshiro128 {
|
|
var x = Xoroshiro128{
|
|
.random = Random{ .fillFn = fill },
|
|
.s = undefined,
|
|
};
|
|
|
|
x.seed(init_s);
|
|
return x;
|
|
}
|
|
|
|
fn next(self: *Xoroshiro128) u64 {
|
|
const s0 = self.s[0];
|
|
var s1 = self.s[1];
|
|
const r = s0 +% s1;
|
|
|
|
s1 ^= s0;
|
|
self.s[0] = math.rotl(u64, s0, u8(55)) ^ s1 ^ (s1 << 14);
|
|
self.s[1] = math.rotl(u64, s1, u8(36));
|
|
|
|
return r;
|
|
}
|
|
|
|
// Skip 2^64 places ahead in the sequence
|
|
fn jump(self: *Xoroshiro128) void {
|
|
var s0: u64 = 0;
|
|
var s1: u64 = 0;
|
|
|
|
const table = [_]u64{
|
|
0xbeac0467eba5facb,
|
|
0xd86b048b86aa9922,
|
|
};
|
|
|
|
inline for (table) |entry| {
|
|
var b: usize = 0;
|
|
while (b < 64) : (b += 1) {
|
|
if ((entry & (u64(1) << @intCast(u6, b))) != 0) {
|
|
s0 ^= self.s[0];
|
|
s1 ^= self.s[1];
|
|
}
|
|
_ = self.next();
|
|
}
|
|
}
|
|
|
|
self.s[0] = s0;
|
|
self.s[1] = s1;
|
|
}
|
|
|
|
fn seed(self: *Xoroshiro128, init_s: u64) void {
|
|
// Xoroshiro requires 128-bits of seed.
|
|
var gen = SplitMix64.init(init_s);
|
|
|
|
self.s[0] = gen.next();
|
|
self.s[1] = gen.next();
|
|
}
|
|
|
|
fn fill(r: *Random, buf: []u8) void {
|
|
const self = @fieldParentPtr(Xoroshiro128, "random", r);
|
|
|
|
var i: usize = 0;
|
|
const aligned_len = buf.len - (buf.len & 7);
|
|
|
|
// Complete 8 byte segments.
|
|
while (i < aligned_len) : (i += 8) {
|
|
var n = self.next();
|
|
comptime var j: usize = 0;
|
|
inline while (j < 8) : (j += 1) {
|
|
buf[i + j] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
|
|
// Remaining. (cuts the stream)
|
|
if (i != buf.len) {
|
|
var n = self.next();
|
|
while (i < buf.len) : (i += 1) {
|
|
buf[i] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
test "xoroshiro sequence" {
|
|
var r = Xoroshiro128.init(0);
|
|
r.s[0] = 0xaeecf86f7878dd75;
|
|
r.s[1] = 0x01cd153642e72622;
|
|
|
|
const seq1 = [_]u64{
|
|
0xb0ba0da5bb600397,
|
|
0x18a08afde614dccc,
|
|
0xa2635b956a31b929,
|
|
0xabe633c971efa045,
|
|
0x9ac19f9706ca3cac,
|
|
0xf62b426578c1e3fb,
|
|
};
|
|
|
|
for (seq1) |s| {
|
|
expect(s == r.next());
|
|
}
|
|
|
|
r.jump();
|
|
|
|
const seq2 = [_]u64{
|
|
0x95344a13556d3e22,
|
|
0xb4fb32dafa4d00df,
|
|
0xb2011d9ccdcfe2dd,
|
|
0x05679a9b2119b908,
|
|
0xa860a1da7c9cd8a0,
|
|
0x658a96efe3f86550,
|
|
};
|
|
|
|
for (seq2) |s| {
|
|
expect(s == r.next());
|
|
}
|
|
}
|
|
|
|
// ISAAC64 - http://www.burtleburtle.net/bob/rand/isaacafa.html
|
|
//
|
|
// CSPRNG
|
|
//
|
|
// Follows the general idea of the implementation from here with a few shortcuts.
|
|
// https://doc.rust-lang.org/rand/src/rand/prng/isaac64.rs.html
|
|
pub const Isaac64 = struct {
|
|
random: Random,
|
|
|
|
r: [256]u64,
|
|
m: [256]u64,
|
|
a: u64,
|
|
b: u64,
|
|
c: u64,
|
|
i: usize,
|
|
|
|
pub fn init(init_s: u64) Isaac64 {
|
|
var isaac = Isaac64{
|
|
.random = Random{ .fillFn = fill },
|
|
.r = undefined,
|
|
.m = undefined,
|
|
.a = undefined,
|
|
.b = undefined,
|
|
.c = undefined,
|
|
.i = undefined,
|
|
};
|
|
|
|
// seed == 0 => same result as the unseeded reference implementation
|
|
isaac.seed(init_s, 1);
|
|
return isaac;
|
|
}
|
|
|
|
fn step(self: *Isaac64, mix: u64, base: usize, comptime m1: usize, comptime m2: usize) void {
|
|
const x = self.m[base + m1];
|
|
self.a = mix +% self.m[base + m2];
|
|
|
|
const y = self.a +% self.b +% self.m[@intCast(usize, (x >> 3) % self.m.len)];
|
|
self.m[base + m1] = y;
|
|
|
|
self.b = x +% self.m[@intCast(usize, (y >> 11) % self.m.len)];
|
|
self.r[self.r.len - 1 - base - m1] = self.b;
|
|
}
|
|
|
|
fn refill(self: *Isaac64) void {
|
|
const midpoint = self.r.len / 2;
|
|
|
|
self.c +%= 1;
|
|
self.b +%= self.c;
|
|
|
|
{
|
|
var i: usize = 0;
|
|
while (i < midpoint) : (i += 4) {
|
|
self.step(~(self.a ^ (self.a << 21)), i + 0, 0, midpoint);
|
|
self.step(self.a ^ (self.a >> 5), i + 1, 0, midpoint);
|
|
self.step(self.a ^ (self.a << 12), i + 2, 0, midpoint);
|
|
self.step(self.a ^ (self.a >> 33), i + 3, 0, midpoint);
|
|
}
|
|
}
|
|
|
|
{
|
|
var i: usize = 0;
|
|
while (i < midpoint) : (i += 4) {
|
|
self.step(~(self.a ^ (self.a << 21)), i + 0, midpoint, 0);
|
|
self.step(self.a ^ (self.a >> 5), i + 1, midpoint, 0);
|
|
self.step(self.a ^ (self.a << 12), i + 2, midpoint, 0);
|
|
self.step(self.a ^ (self.a >> 33), i + 3, midpoint, 0);
|
|
}
|
|
}
|
|
|
|
self.i = 0;
|
|
}
|
|
|
|
fn next(self: *Isaac64) u64 {
|
|
if (self.i >= self.r.len) {
|
|
self.refill();
|
|
}
|
|
|
|
const value = self.r[self.i];
|
|
self.i += 1;
|
|
return value;
|
|
}
|
|
|
|
fn seed(self: *Isaac64, init_s: u64, comptime rounds: usize) void {
|
|
// We ignore the multi-pass requirement since we don't currently expose full access to
|
|
// seeding the self.m array completely.
|
|
mem.set(u64, self.m[0..], 0);
|
|
self.m[0] = init_s;
|
|
|
|
// prescrambled golden ratio constants
|
|
var a = [_]u64{
|
|
0x647c4677a2884b7c,
|
|
0xb9f8b322c73ac862,
|
|
0x8c0ea5053d4712a0,
|
|
0xb29b2e824a595524,
|
|
0x82f053db8355e0ce,
|
|
0x48fe4a0fa5a09315,
|
|
0xae985bf2cbfc89ed,
|
|
0x98f5704f6c44c0ab,
|
|
};
|
|
|
|
comptime var i: usize = 0;
|
|
inline while (i < rounds) : (i += 1) {
|
|
var j: usize = 0;
|
|
while (j < self.m.len) : (j += 8) {
|
|
comptime var x1: usize = 0;
|
|
inline while (x1 < 8) : (x1 += 1) {
|
|
a[x1] +%= self.m[j + x1];
|
|
}
|
|
|
|
a[0] -%= a[4];
|
|
a[5] ^= a[7] >> 9;
|
|
a[7] +%= a[0];
|
|
a[1] -%= a[5];
|
|
a[6] ^= a[0] << 9;
|
|
a[0] +%= a[1];
|
|
a[2] -%= a[6];
|
|
a[7] ^= a[1] >> 23;
|
|
a[1] +%= a[2];
|
|
a[3] -%= a[7];
|
|
a[0] ^= a[2] << 15;
|
|
a[2] +%= a[3];
|
|
a[4] -%= a[0];
|
|
a[1] ^= a[3] >> 14;
|
|
a[3] +%= a[4];
|
|
a[5] -%= a[1];
|
|
a[2] ^= a[4] << 20;
|
|
a[4] +%= a[5];
|
|
a[6] -%= a[2];
|
|
a[3] ^= a[5] >> 17;
|
|
a[5] +%= a[6];
|
|
a[7] -%= a[3];
|
|
a[4] ^= a[6] << 14;
|
|
a[6] +%= a[7];
|
|
|
|
comptime var x2: usize = 0;
|
|
inline while (x2 < 8) : (x2 += 1) {
|
|
self.m[j + x2] = a[x2];
|
|
}
|
|
}
|
|
}
|
|
|
|
mem.set(u64, self.r[0..], 0);
|
|
self.a = 0;
|
|
self.b = 0;
|
|
self.c = 0;
|
|
self.i = self.r.len; // trigger refill on first value
|
|
}
|
|
|
|
fn fill(r: *Random, buf: []u8) void {
|
|
const self = @fieldParentPtr(Isaac64, "random", r);
|
|
|
|
var i: usize = 0;
|
|
const aligned_len = buf.len - (buf.len & 7);
|
|
|
|
// Fill complete 64-byte segments
|
|
while (i < aligned_len) : (i += 8) {
|
|
var n = self.next();
|
|
comptime var j: usize = 0;
|
|
inline while (j < 8) : (j += 1) {
|
|
buf[i + j] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
|
|
// Fill trailing, ignoring excess (cut the stream).
|
|
if (i != buf.len) {
|
|
var n = self.next();
|
|
while (i < buf.len) : (i += 1) {
|
|
buf[i] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
test "isaac64 sequence" {
|
|
var r = Isaac64.init(0);
|
|
|
|
// from reference implementation
|
|
const seq = [_]u64{
|
|
0xf67dfba498e4937c,
|
|
0x84a5066a9204f380,
|
|
0xfee34bd5f5514dbb,
|
|
0x4d1664739b8f80d6,
|
|
0x8607459ab52a14aa,
|
|
0x0e78bc5a98529e49,
|
|
0xfe5332822ad13777,
|
|
0x556c27525e33d01a,
|
|
0x08643ca615f3149f,
|
|
0xd0771faf3cb04714,
|
|
0x30e86f68a37b008d,
|
|
0x3074ebc0488a3adf,
|
|
0x270645ea7a2790bc,
|
|
0x5601a0a8d3763c6a,
|
|
0x2f83071f53f325dd,
|
|
0xb9090f3d42d2d2ea,
|
|
};
|
|
|
|
for (seq) |s| {
|
|
expect(s == r.next());
|
|
}
|
|
}
|
|
|
|
/// Sfc64 pseudo-random number generator from Practically Random.
|
|
/// Fastest engine of pracrand and smallest footprint.
|
|
/// See http://pracrand.sourceforge.net/
|
|
pub const Sfc64 = struct {
|
|
random: Random,
|
|
|
|
a: u64 = undefined,
|
|
b: u64 = undefined,
|
|
c: u64 = undefined,
|
|
counter: u64 = undefined,
|
|
|
|
const Rotation = 24;
|
|
const RightShift = 11;
|
|
const LeftShift = 3;
|
|
|
|
pub fn init(init_s: u64) Sfc64 {
|
|
var x = Sfc64{
|
|
.random = Random{ .fillFn = fill },
|
|
};
|
|
|
|
x.seed(init_s);
|
|
return x;
|
|
}
|
|
|
|
fn next(self: *Sfc64) u64 {
|
|
const tmp = self.a +% self.b +% self.counter;
|
|
self.counter += 1;
|
|
self.a = self.b ^ (self.b >> RightShift);
|
|
self.b = self.c +% (self.c << LeftShift);
|
|
self.c = math.rotl(u64, self.c, Rotation) +% tmp;
|
|
return tmp;
|
|
}
|
|
|
|
fn seed(self: *Sfc64, init_s: u64) void {
|
|
self.a = init_s;
|
|
self.b = init_s;
|
|
self.c = init_s;
|
|
self.counter = 1;
|
|
var i: u32 = 0;
|
|
while (i < 12) : (i += 1) {
|
|
_ = self.next();
|
|
}
|
|
}
|
|
|
|
fn fill(r: *Random, buf: []u8) void {
|
|
const self = @fieldParentPtr(Sfc64, "random", r);
|
|
|
|
var i: usize = 0;
|
|
const aligned_len = buf.len - (buf.len & 7);
|
|
|
|
// Complete 8 byte segments.
|
|
while (i < aligned_len) : (i += 8) {
|
|
var n = self.next();
|
|
comptime var j: usize = 0;
|
|
inline while (j < 8) : (j += 1) {
|
|
buf[i + j] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
|
|
// Remaining. (cuts the stream)
|
|
if (i != buf.len) {
|
|
var n = self.next();
|
|
while (i < buf.len) : (i += 1) {
|
|
buf[i] = @truncate(u8, n);
|
|
n >>= 8;
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
test "Sfc64 sequence" {
|
|
// Unfortunately there does not seem to be an official test sequence.
|
|
var r = Sfc64.init(0);
|
|
|
|
const seq = [_]u64{
|
|
0x3acfa029e3cc6041,
|
|
0xf5b6515bf2ee419c,
|
|
0x1259635894a29b61,
|
|
0xb6ae75395f8ebd6,
|
|
0x225622285ce302e2,
|
|
0x520d28611395cb21,
|
|
0xdb909c818901599d,
|
|
0x8ffd195365216f57,
|
|
0xe8c4ad5e258ac04a,
|
|
0x8f8ef2c89fdb63ca,
|
|
0xf9865b01d98d8e2f,
|
|
0x46555871a65d08ba,
|
|
0x66868677c6298fcd,
|
|
0x2ce15a7e6329f57d,
|
|
0xb2f1833ca91ca79,
|
|
0x4b0890ac9bf453ca,
|
|
};
|
|
|
|
for (seq) |s| {
|
|
expectEqual(s, r.next());
|
|
}
|
|
}
|
|
|
|
// Actual Random helper function tests, pcg engine is assumed correct.
|
|
test "Random float" {
|
|
var prng = DefaultPrng.init(0);
|
|
|
|
var i: usize = 0;
|
|
while (i < 1000) : (i += 1) {
|
|
const val1 = prng.random.float(f32);
|
|
expect(val1 >= 0.0);
|
|
expect(val1 < 1.0);
|
|
|
|
const val2 = prng.random.float(f64);
|
|
expect(val2 >= 0.0);
|
|
expect(val2 < 1.0);
|
|
}
|
|
}
|
|
|
|
test "Random shuffle" {
|
|
var prng = DefaultPrng.init(0);
|
|
|
|
var seq = [_]u8{ 0, 1, 2, 3, 4 };
|
|
var seen = [_]bool{false} ** 5;
|
|
|
|
var i: usize = 0;
|
|
while (i < 1000) : (i += 1) {
|
|
prng.random.shuffle(u8, seq[0..]);
|
|
seen[seq[0]] = true;
|
|
expect(sumArray(seq[0..]) == 10);
|
|
}
|
|
|
|
// we should see every entry at the head at least once
|
|
for (seen) |e| {
|
|
expect(e == true);
|
|
}
|
|
}
|
|
|
|
fn sumArray(s: []const u8) u32 {
|
|
var r: u32 = 0;
|
|
for (s) |e|
|
|
r += e;
|
|
return r;
|
|
}
|
|
|
|
test "Random range" {
|
|
var prng = DefaultPrng.init(0);
|
|
testRange(&prng.random, -4, 3);
|
|
testRange(&prng.random, -4, -1);
|
|
testRange(&prng.random, 10, 14);
|
|
testRange(&prng.random, -0x80, 0x7f);
|
|
}
|
|
|
|
fn testRange(r: *Random, start: i8, end: i8) void {
|
|
testRangeBias(r, start, end, true);
|
|
testRangeBias(r, start, end, false);
|
|
}
|
|
fn testRangeBias(r: *Random, start: i8, end: i8, biased: bool) void {
|
|
const count = @intCast(usize, i32(end) - i32(start));
|
|
var values_buffer = [_]bool{false} ** 0x100;
|
|
const values = values_buffer[0..count];
|
|
var i: usize = 0;
|
|
while (i < count) {
|
|
const value: i32 = if (biased) r.intRangeLessThanBiased(i8, start, end) else r.intRangeLessThan(i8, start, end);
|
|
const index = @intCast(usize, value - start);
|
|
if (!values[index]) {
|
|
i += 1;
|
|
values[index] = true;
|
|
}
|
|
}
|
|
}
|