authorgravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2022-05-10 22:03:29-04:00
committergravatar for noreply@github.comGitHub <noreply@github.com> 2022-05-10 22:03:29-04:00
loged63d6c7fdbdc3c508457ca792436595dd443ac8
tree1fc0bfeae8cbb443d7ab416b0308a0db1149ab8a
parente0a514df41cdf40b0e99ba48b86143bfc03dd3aa
parent7bedeb9659af84daab33a4804c54b4c8811c0c5d
signaturebadge-question-mark Signed by PGP key 4AEE18F83AFDEB23

Merge pull request #10428 from mrakh/rand_float_improvement

Improve stdlib's random float generation

2 files changed, 489 insertions(+), 326 deletions(-)

lib/std/rand.zig+42-326
......@@ -9,8 +9,6 @@
99const std = @import("std.zig");
1010const builtin = @import("builtin");
1111const assert = std.debug.assert;
12const expect = std.testing.expect;
13const expectEqual = std.testing.expectEqual;
1412const mem = std.mem;
1513const math = std.math;
1614const ziggurat = @import("rand/ziggurat.zig");
......@@ -249,18 +247,51 @@ pub const Random = struct {
249247
250248 /// Return a floating point value evenly distributed in the range [0, 1).
251249 pub fn float(r: Random, comptime T: type) T {
252 // Generate a uniform value between [1, 2) and scale down to [0, 1).
253 // Note: The lowest mantissa bit is always set to 0 so we only use half the available range.
250 // Generate a uniformly random value between for the mantissa.
251 // Then generate an exponentially biased random value for the exponent.
252 // Over the previous method, this has the advantage of being able to
253 // represent every possible value in the available range.
254254 switch (T) {
255255 f32 => {
256 const s = r.int(u32);
257 const repr = (0x7f << 23) | (s >> 9);
258 return @bitCast(f32, repr) - 1.0;
256 // Use 23 random bits for the mantissa, and the rest for the exponent.
257 // If all 41 bits are zero, generate additional random bits, until a
258 // set bit is found, or 126 bits have been generated.
259 const rand = r.int(u64);
260 var rand_lz = @clz(u64, rand | 0x7FFFFF);
261 if (rand_lz == 41) {
262 rand_lz += @clz(u64, r.int(u64));
263 if (rand_lz == 41 + 64) {
264 // It is astronomically unlikely to reach this point.
265 rand_lz += @clz(u32, r.int(u32) | 0x7FF);
266 }
267 }
268 const mantissa = @truncate(u23, rand);
269 const exponent = @as(u32, 126 - rand_lz) << 23;
270 return @bitCast(f32, exponent | mantissa);
259271 },
260272 f64 => {
261 const s = r.int(u64);
262 const repr = (0x3ff << 52) | (s >> 12);
263 return @bitCast(f64, repr) - 1.0;
273 // Use 52 random bits for the mantissa, and the rest for the exponent.
274 // If all 12 bits are zero, generate additional random bits, until a
275 // set bit is found, or 1022 bits have been generated.
276 const rand = r.int(u64);
277 var rand_lz: u64 = @clz(u64, rand | 0xFFFFFFFFFFFFF);
278 if (rand_lz == 12) {
279 while (true) {
280 // It is astronomically unlikely for this loop to execute more than once.
281 const addl_rand_lz = @clz(u64, r.int(u64));
282 rand_lz += addl_rand_lz;
283 if (addl_rand_lz != 64) {
284 break;
285 }
286 if (rand_lz >= 1022) {
287 rand_lz = 1022;
288 break;
289 }
290 }
291 }
292 const mantissa = rand & 0xFFFFFFFFFFFFF;
293 const exponent = (1022 - rand_lz) << 52;
294 return @bitCast(f64, exponent | mantissa);
264295 },
265296 else => @compileError("unknown floating point type"),
266297 }
......@@ -319,221 +350,6 @@ pub fn limitRangeBiased(comptime T: type, random_int: T, less_than: T) T {
319350 return @intCast(T, m >> bits);
320351}
321352
322const SequentialPrng = struct {
323 const Self = @This();
324 next_value: u8,
325
326 pub fn init() Self {
327 return Self{
328 .next_value = 0,
329 };
330 }
331
332 pub fn random(self: *Self) Random {
333 return Random.init(self, fill);
334 }
335
336 pub fn fill(self: *Self, buf: []u8) void {
337 for (buf) |*b| {
338 b.* = self.next_value;
339 }
340 self.next_value +%= 1;
341 }
342};
343
344test "Random int" {
345 try testRandomInt();
346 comptime try testRandomInt();
347}
348fn testRandomInt() !void {
349 var rng = SequentialPrng.init();
350 const random = rng.random();
351
352 try expect(random.int(u0) == 0);
353
354 rng.next_value = 0;
355 try expect(random.int(u1) == 0);
356 try expect(random.int(u1) == 1);
357 try expect(random.int(u2) == 2);
358 try expect(random.int(u2) == 3);
359 try expect(random.int(u2) == 0);
360
361 rng.next_value = 0xff;
362 try expect(random.int(u8) == 0xff);
363 rng.next_value = 0x11;
364 try expect(random.int(u8) == 0x11);
365
366 rng.next_value = 0xff;
367 try expect(random.int(u32) == 0xffffffff);
368 rng.next_value = 0x11;
369 try expect(random.int(u32) == 0x11111111);
370
371 rng.next_value = 0xff;
372 try expect(random.int(i32) == -1);
373 rng.next_value = 0x11;
374 try expect(random.int(i32) == 0x11111111);
375
376 rng.next_value = 0xff;
377 try expect(random.int(i8) == -1);
378 rng.next_value = 0x11;
379 try expect(random.int(i8) == 0x11);
380
381 rng.next_value = 0xff;
382 try expect(random.int(u33) == 0x1ffffffff);
383 rng.next_value = 0xff;
384 try expect(random.int(i1) == -1);
385 rng.next_value = 0xff;
386 try expect(random.int(i2) == -1);
387 rng.next_value = 0xff;
388 try expect(random.int(i33) == -1);
389}
390
391test "Random boolean" {
392 try testRandomBoolean();
393 comptime try testRandomBoolean();
394}
395fn testRandomBoolean() !void {
396 var rng = SequentialPrng.init();
397 const random = rng.random();
398
399 try expect(random.boolean() == false);
400 try expect(random.boolean() == true);
401 try expect(random.boolean() == false);
402 try expect(random.boolean() == true);
403}
404
405test "Random enum" {
406 try testRandomEnumValue();
407 comptime try testRandomEnumValue();
408}
409fn testRandomEnumValue() !void {
410 const TestEnum = enum {
411 First,
412 Second,
413 Third,
414 };
415 var rng = SequentialPrng.init();
416 const random = rng.random();
417 rng.next_value = 0;
418 try expect(random.enumValue(TestEnum) == TestEnum.First);
419 try expect(random.enumValue(TestEnum) == TestEnum.First);
420 try expect(random.enumValue(TestEnum) == TestEnum.First);
421}
422
423test "Random intLessThan" {
424 @setEvalBranchQuota(10000);
425 try testRandomIntLessThan();
426 comptime try testRandomIntLessThan();
427}
428fn testRandomIntLessThan() !void {
429 var rng = SequentialPrng.init();
430 const random = rng.random();
431
432 rng.next_value = 0xff;
433 try expect(random.uintLessThan(u8, 4) == 3);
434 try expect(rng.next_value == 0);
435 try expect(random.uintLessThan(u8, 4) == 0);
436 try expect(rng.next_value == 1);
437
438 rng.next_value = 0;
439 try expect(random.uintLessThan(u64, 32) == 0);
440
441 // trigger the bias rejection code path
442 rng.next_value = 0;
443 try expect(random.uintLessThan(u8, 3) == 0);
444 // verify we incremented twice
445 try expect(rng.next_value == 2);
446
447 rng.next_value = 0xff;
448 try expect(random.intRangeLessThan(u8, 0, 0x80) == 0x7f);
449 rng.next_value = 0xff;
450 try expect(random.intRangeLessThan(u8, 0x7f, 0xff) == 0xfe);
451
452 rng.next_value = 0xff;
453 try expect(random.intRangeLessThan(i8, 0, 0x40) == 0x3f);
454 rng.next_value = 0xff;
455 try expect(random.intRangeLessThan(i8, -0x40, 0x40) == 0x3f);
456 rng.next_value = 0xff;
457 try expect(random.intRangeLessThan(i8, -0x80, 0) == -1);
458
459 rng.next_value = 0xff;
460 try expect(random.intRangeLessThan(i3, -4, 0) == -1);
461 rng.next_value = 0xff;
462 try expect(random.intRangeLessThan(i3, -2, 2) == 1);
463}
464
465test "Random intAtMost" {
466 @setEvalBranchQuota(10000);
467 try testRandomIntAtMost();
468 comptime try testRandomIntAtMost();
469}
470fn testRandomIntAtMost() !void {
471 var rng = SequentialPrng.init();
472 const random = rng.random();
473
474 rng.next_value = 0xff;
475 try expect(random.uintAtMost(u8, 3) == 3);
476 try expect(rng.next_value == 0);
477 try expect(random.uintAtMost(u8, 3) == 0);
478
479 // trigger the bias rejection code path
480 rng.next_value = 0;
481 try expect(random.uintAtMost(u8, 2) == 0);
482 // verify we incremented twice
483 try expect(rng.next_value == 2);
484
485 rng.next_value = 0xff;
486 try expect(random.intRangeAtMost(u8, 0, 0x7f) == 0x7f);
487 rng.next_value = 0xff;
488 try expect(random.intRangeAtMost(u8, 0x7f, 0xfe) == 0xfe);
489
490 rng.next_value = 0xff;
491 try expect(random.intRangeAtMost(i8, 0, 0x3f) == 0x3f);
492 rng.next_value = 0xff;
493 try expect(random.intRangeAtMost(i8, -0x40, 0x3f) == 0x3f);
494 rng.next_value = 0xff;
495 try expect(random.intRangeAtMost(i8, -0x80, -1) == -1);
496
497 rng.next_value = 0xff;
498 try expect(random.intRangeAtMost(i3, -4, -1) == -1);
499 rng.next_value = 0xff;
500 try expect(random.intRangeAtMost(i3, -2, 1) == 1);
501
502 try expect(random.uintAtMost(u0, 0) == 0);
503}
504
505test "Random Biased" {
506 var prng = DefaultPrng.init(0);
507 const random = prng.random();
508 // Not thoroughly checking the logic here.
509 // Just want to execute all the paths with different types.
510
511 try expect(random.uintLessThanBiased(u1, 1) == 0);
512 try expect(random.uintLessThanBiased(u32, 10) < 10);
513 try expect(random.uintLessThanBiased(u64, 20) < 20);
514
515 try expect(random.uintAtMostBiased(u0, 0) == 0);
516 try expect(random.uintAtMostBiased(u1, 0) <= 0);
517 try expect(random.uintAtMostBiased(u32, 10) <= 10);
518 try expect(random.uintAtMostBiased(u64, 20) <= 20);
519
520 try expect(random.intRangeLessThanBiased(u1, 0, 1) == 0);
521 try expect(random.intRangeLessThanBiased(i1, -1, 0) == -1);
522 try expect(random.intRangeLessThanBiased(u32, 10, 20) >= 10);
523 try expect(random.intRangeLessThanBiased(i32, 10, 20) >= 10);
524 try expect(random.intRangeLessThanBiased(u64, 20, 40) >= 20);
525 try expect(random.intRangeLessThanBiased(i64, 20, 40) >= 20);
526
527 // uncomment for broken module error:
528 //expect(random.intRangeAtMostBiased(u0, 0, 0) == 0);
529 try expect(random.intRangeAtMostBiased(u1, 0, 1) >= 0);
530 try expect(random.intRangeAtMostBiased(i1, -1, 0) >= -1);
531 try expect(random.intRangeAtMostBiased(u32, 10, 20) >= 10);
532 try expect(random.intRangeAtMostBiased(i32, 10, 20) >= 10);
533 try expect(random.intRangeAtMostBiased(u64, 20, 40) >= 20);
534 try expect(random.intRangeAtMostBiased(i64, 20, 40) >= 20);
535}
536
537353// Generator to extend 64-bit seed values into longer sequences.
538354//
539355// The number of cycles is thus limited to 64-bits regardless of the engine, but this
......@@ -555,107 +371,7 @@ pub const SplitMix64 = struct {
555371 }
556372};
557373
558test "splitmix64 sequence" {
559 var r = SplitMix64.init(0xaeecf86f7878dd75);
560
561 const seq = [_]u64{
562 0x5dbd39db0178eb44,
563 0xa9900fb66b397da3,
564 0x5c1a28b1aeebcf5c,
565 0x64a963238f776912,
566 0xc6d4177b21d1c0ab,
567 0xb2cbdbdb5ea35394,
568 };
569
570 for (seq) |s| {
571 try expect(s == r.next());
572 }
573}
574
575// Actual Random helper function tests, pcg engine is assumed correct.
576test "Random float" {
577 var prng = DefaultPrng.init(0);
578 const random = prng.random();
579
580 var i: usize = 0;
581 while (i < 1000) : (i += 1) {
582 const val1 = random.float(f32);
583 try expect(val1 >= 0.0);
584 try expect(val1 < 1.0);
585
586 const val2 = random.float(f64);
587 try expect(val2 >= 0.0);
588 try expect(val2 < 1.0);
589 }
590}
591
592test "Random shuffle" {
593 var prng = DefaultPrng.init(0);
594 const random = prng.random();
595
596 var seq = [_]u8{ 0, 1, 2, 3, 4 };
597 var seen = [_]bool{false} ** 5;
598
599 var i: usize = 0;
600 while (i < 1000) : (i += 1) {
601 random.shuffle(u8, seq[0..]);
602 seen[seq[0]] = true;
603 try expect(sumArray(seq[0..]) == 10);
604 }
605
606 // we should see every entry at the head at least once
607 for (seen) |e| {
608 try expect(e == true);
609 }
610}
611
612fn sumArray(s: []const u8) u32 {
613 var r: u32 = 0;
614 for (s) |e|
615 r += e;
616 return r;
617}
618
619test "Random range" {
620 var prng = DefaultPrng.init(0);
621 const random = prng.random();
622
623 try testRange(random, -4, 3);
624 try testRange(random, -4, -1);
625 try testRange(random, 10, 14);
626 try testRange(random, -0x80, 0x7f);
627}
628
629fn testRange(r: Random, start: i8, end: i8) !void {
630 try testRangeBias(r, start, end, true);
631 try testRangeBias(r, start, end, false);
632}
633fn testRangeBias(r: Random, start: i8, end: i8, biased: bool) !void {
634 const count = @intCast(usize, @as(i32, end) - @as(i32, start));
635 var values_buffer = [_]bool{false} ** 0x100;
636 const values = values_buffer[0..count];
637 var i: usize = 0;
638 while (i < count) {
639 const value: i32 = if (biased) r.intRangeLessThanBiased(i8, start, end) else r.intRangeLessThan(i8, start, end);
640 const index = @intCast(usize, value - start);
641 if (!values[index]) {
642 i += 1;
643 values[index] = true;
644 }
645 }
646}
647
648test "CSPRNG" {
649 var secret_seed: [DefaultCsprng.secret_seed_length]u8 = undefined;
650 std.crypto.random.bytes(&secret_seed);
651 var csprng = DefaultCsprng.init(secret_seed);
652 const random = csprng.random();
653 const a = random.int(u64);
654 const b = random.int(u64);
655 const c = random.int(u64);
656 try expect(a ^ b ^ c != 0);
657}
658
659374test {
660375 std.testing.refAllDecls(@This());
376 _ = @import("rand/test.zig");
661377}
lib/std/rand/test.zig created+447
......@@ -0,0 +1,447 @@
1const std = @import("../std.zig");
2const math = std.math;
3const DefaultPrng = std.rand.DefaultPrng;
4const Random = std.rand.Random;
5const SplitMix64 = std.rand.SplitMix64;
6const DefaultCsprng = std.rand.DefaultCsprng;
7const expect = std.testing.expect;
8const expectEqual = std.testing.expectEqual;
9
10const SequentialPrng = struct {
11 const Self = @This();
12 next_value: u8,
13
14 pub fn init() Self {
15 return Self{
16 .next_value = 0,
17 };
18 }
19
20 pub fn random(self: *Self) Random {
21 return Random.init(self, fill);
22 }
23
24 pub fn fill(self: *Self, buf: []u8) void {
25 for (buf) |*b| {
26 b.* = self.next_value;
27 }
28 self.next_value +%= 1;
29 }
30};
31
32/// Do not use this PRNG! It is meant to be predictable, for the purposes of test reproducibility and coverage.
33/// Its output is just a repeat of a user-specified byte pattern.
34/// Name is a reference to this comic: https://dilbert.com/strip/2001-10-25
35const Dilbert = struct {
36 pattern: []const u8 = undefined,
37 curr_idx: usize = 0,
38
39 pub fn init(pattern: []const u8) !Dilbert {
40 if (pattern.len == 0)
41 return error.EmptyPattern;
42 var self = Dilbert{};
43 self.pattern = pattern;
44 self.curr_idx = 0;
45 return self;
46 }
47
48 pub fn random(self: *Dilbert) Random {
49 return Random.init(self, fill);
50 }
51
52 pub fn fill(self: *Dilbert, buf: []u8) void {
53 for (buf) |*byte| {
54 byte.* = self.pattern[self.curr_idx];
55 self.curr_idx = (self.curr_idx + 1) % self.pattern.len;
56 }
57 }
58
59 test "Dilbert fill" {
60 var r = try Dilbert.init("9nine");
61
62 const seq = [_]u64{
63 0x396E696E65396E69,
64 0x6E65396E696E6539,
65 0x6E696E65396E696E,
66 0x65396E696E65396E,
67 0x696E65396E696E65,
68 };
69
70 for (seq) |s| {
71 var buf0: [8]u8 = undefined;
72 var buf1: [8]u8 = undefined;
73 std.mem.writeIntBig(u64, &buf0, s);
74 r.fill(&buf1);
75 try std.testing.expect(std.mem.eql(u8, buf0[0..], buf1[0..]));
76 }
77 }
78};
79
80test "Random int" {
81 try testRandomInt();
82 comptime try testRandomInt();
83}
84fn testRandomInt() !void {
85 var rng = SequentialPrng.init();
86 const random = rng.random();
87
88 try expect(random.int(u0) == 0);
89
90 rng.next_value = 0;
91 try expect(random.int(u1) == 0);
92 try expect(random.int(u1) == 1);
93 try expect(random.int(u2) == 2);
94 try expect(random.int(u2) == 3);
95 try expect(random.int(u2) == 0);
96
97 rng.next_value = 0xff;
98 try expect(random.int(u8) == 0xff);
99 rng.next_value = 0x11;
100 try expect(random.int(u8) == 0x11);
101
102 rng.next_value = 0xff;
103 try expect(random.int(u32) == 0xffffffff);
104 rng.next_value = 0x11;
105 try expect(random.int(u32) == 0x11111111);
106
107 rng.next_value = 0xff;
108 try expect(random.int(i32) == -1);
109 rng.next_value = 0x11;
110 try expect(random.int(i32) == 0x11111111);
111
112 rng.next_value = 0xff;
113 try expect(random.int(i8) == -1);
114 rng.next_value = 0x11;
115 try expect(random.int(i8) == 0x11);
116
117 rng.next_value = 0xff;
118 try expect(random.int(u33) == 0x1ffffffff);
119 rng.next_value = 0xff;
120 try expect(random.int(i1) == -1);
121 rng.next_value = 0xff;
122 try expect(random.int(i2) == -1);
123 rng.next_value = 0xff;
124 try expect(random.int(i33) == -1);
125}
126
127test "Random boolean" {
128 try testRandomBoolean();
129 comptime try testRandomBoolean();
130}
131fn testRandomBoolean() !void {
132 var rng = SequentialPrng.init();
133 const random = rng.random();
134
135 try expect(random.boolean() == false);
136 try expect(random.boolean() == true);
137 try expect(random.boolean() == false);
138 try expect(random.boolean() == true);
139}
140
141test "Random enum" {
142 try testRandomEnumValue();
143 comptime try testRandomEnumValue();
144}
145fn testRandomEnumValue() !void {
146 const TestEnum = enum {
147 First,
148 Second,
149 Third,
150 };
151 var rng = SequentialPrng.init();
152 const random = rng.random();
153 rng.next_value = 0;
154 try expect(random.enumValue(TestEnum) == TestEnum.First);
155 try expect(random.enumValue(TestEnum) == TestEnum.First);
156 try expect(random.enumValue(TestEnum) == TestEnum.First);
157}
158
159test "Random intLessThan" {
160 @setEvalBranchQuota(10000);
161 try testRandomIntLessThan();
162 comptime try testRandomIntLessThan();
163}
164fn testRandomIntLessThan() !void {
165 var rng = SequentialPrng.init();
166 const random = rng.random();
167
168 rng.next_value = 0xff;
169 try expect(random.uintLessThan(u8, 4) == 3);
170 try expect(rng.next_value == 0);
171 try expect(random.uintLessThan(u8, 4) == 0);
172 try expect(rng.next_value == 1);
173
174 rng.next_value = 0;
175 try expect(random.uintLessThan(u64, 32) == 0);
176
177 // trigger the bias rejection code path
178 rng.next_value = 0;
179 try expect(random.uintLessThan(u8, 3) == 0);
180 // verify we incremented twice
181 try expect(rng.next_value == 2);
182
183 rng.next_value = 0xff;
184 try expect(random.intRangeLessThan(u8, 0, 0x80) == 0x7f);
185 rng.next_value = 0xff;
186 try expect(random.intRangeLessThan(u8, 0x7f, 0xff) == 0xfe);
187
188 rng.next_value = 0xff;
189 try expect(random.intRangeLessThan(i8, 0, 0x40) == 0x3f);
190 rng.next_value = 0xff;
191 try expect(random.intRangeLessThan(i8, -0x40, 0x40) == 0x3f);
192 rng.next_value = 0xff;
193 try expect(random.intRangeLessThan(i8, -0x80, 0) == -1);
194
195 rng.next_value = 0xff;
196 try expect(random.intRangeLessThan(i3, -4, 0) == -1);
197 rng.next_value = 0xff;
198 try expect(random.intRangeLessThan(i3, -2, 2) == 1);
199}
200
201test "Random intAtMost" {
202 @setEvalBranchQuota(10000);
203 try testRandomIntAtMost();
204 comptime try testRandomIntAtMost();
205}
206fn testRandomIntAtMost() !void {
207 var rng = SequentialPrng.init();
208 const random = rng.random();
209
210 rng.next_value = 0xff;
211 try expect(random.uintAtMost(u8, 3) == 3);
212 try expect(rng.next_value == 0);
213 try expect(random.uintAtMost(u8, 3) == 0);
214
215 // trigger the bias rejection code path
216 rng.next_value = 0;
217 try expect(random.uintAtMost(u8, 2) == 0);
218 // verify we incremented twice
219 try expect(rng.next_value == 2);
220
221 rng.next_value = 0xff;
222 try expect(random.intRangeAtMost(u8, 0, 0x7f) == 0x7f);
223 rng.next_value = 0xff;
224 try expect(random.intRangeAtMost(u8, 0x7f, 0xfe) == 0xfe);
225
226 rng.next_value = 0xff;
227 try expect(random.intRangeAtMost(i8, 0, 0x3f) == 0x3f);
228 rng.next_value = 0xff;
229 try expect(random.intRangeAtMost(i8, -0x40, 0x3f) == 0x3f);
230 rng.next_value = 0xff;
231 try expect(random.intRangeAtMost(i8, -0x80, -1) == -1);
232
233 rng.next_value = 0xff;
234 try expect(random.intRangeAtMost(i3, -4, -1) == -1);
235 rng.next_value = 0xff;
236 try expect(random.intRangeAtMost(i3, -2, 1) == 1);
237
238 try expect(random.uintAtMost(u0, 0) == 0);
239}
240
241test "Random Biased" {
242 var prng = DefaultPrng.init(0);
243 const random = prng.random();
244 // Not thoroughly checking the logic here.
245 // Just want to execute all the paths with different types.
246
247 try expect(random.uintLessThanBiased(u1, 1) == 0);
248 try expect(random.uintLessThanBiased(u32, 10) < 10);
249 try expect(random.uintLessThanBiased(u64, 20) < 20);
250
251 try expect(random.uintAtMostBiased(u0, 0) == 0);
252 try expect(random.uintAtMostBiased(u1, 0) <= 0);
253 try expect(random.uintAtMostBiased(u32, 10) <= 10);
254 try expect(random.uintAtMostBiased(u64, 20) <= 20);
255
256 try expect(random.intRangeLessThanBiased(u1, 0, 1) == 0);
257 try expect(random.intRangeLessThanBiased(i1, -1, 0) == -1);
258 try expect(random.intRangeLessThanBiased(u32, 10, 20) >= 10);
259 try expect(random.intRangeLessThanBiased(i32, 10, 20) >= 10);
260 try expect(random.intRangeLessThanBiased(u64, 20, 40) >= 20);
261 try expect(random.intRangeLessThanBiased(i64, 20, 40) >= 20);
262
263 // uncomment for broken module error:
264 //expect(random.intRangeAtMostBiased(u0, 0, 0) == 0);
265 try expect(random.intRangeAtMostBiased(u1, 0, 1) >= 0);
266 try expect(random.intRangeAtMostBiased(i1, -1, 0) >= -1);
267 try expect(random.intRangeAtMostBiased(u32, 10, 20) >= 10);
268 try expect(random.intRangeAtMostBiased(i32, 10, 20) >= 10);
269 try expect(random.intRangeAtMostBiased(u64, 20, 40) >= 20);
270 try expect(random.intRangeAtMostBiased(i64, 20, 40) >= 20);
271}
272
273test "splitmix64 sequence" {
274 var r = SplitMix64.init(0xaeecf86f7878dd75);
275
276 const seq = [_]u64{
277 0x5dbd39db0178eb44,
278 0xa9900fb66b397da3,
279 0x5c1a28b1aeebcf5c,
280 0x64a963238f776912,
281 0xc6d4177b21d1c0ab,
282 0xb2cbdbdb5ea35394,
283 };
284
285 for (seq) |s| {
286 try expect(s == r.next());
287 }
288}
289
290// Actual Random helper function tests, pcg engine is assumed correct.
291test "Random float correctness" {
292 var prng = DefaultPrng.init(0);
293 const random = prng.random();
294
295 var i: usize = 0;
296 while (i < 1000) : (i += 1) {
297 const val1 = random.float(f32);
298 try expect(val1 >= 0.0);
299 try expect(val1 < 1.0);
300
301 const val2 = random.float(f64);
302 try expect(val2 >= 0.0);
303 try expect(val2 < 1.0);
304 }
305}
306
307// Check the "astronomically unlikely" code paths.
308test "Random float coverage" {
309 var prng = try Dilbert.init(&[_]u8{0});
310 const random = prng.random();
311
312 const rand_f64 = random.float(f64);
313 const rand_f32 = random.float(f32);
314
315 try expect(rand_f32 == 0.0);
316 try expect(rand_f64 == 0.0);
317}
318
319test "Random float chi-square goodness of fit" {
320 const num_numbers = 100000;
321 const num_buckets = 1000;
322
323 var f32_hist = std.AutoHashMap(u32, u32).init(std.testing.allocator);
324 defer f32_hist.deinit();
325 var f64_hist = std.AutoHashMap(u64, u32).init(std.testing.allocator);
326 defer f64_hist.deinit();
327
328 var prng = DefaultPrng.init(0);
329 const random = prng.random();
330
331 var i: usize = 0;
332 while (i < num_numbers) : (i += 1) {
333 const rand_f32 = random.float(f32);
334 const rand_f64 = random.float(f64);
335 var f32_put = try f32_hist.getOrPut(@floatToInt(u32, rand_f32 * @intToFloat(f32, num_buckets)));
336 if (f32_put.found_existing) {
337 f32_put.value_ptr.* += 1;
338 } else {
339 f32_put.value_ptr.* = 0;
340 }
341 var f64_put = try f64_hist.getOrPut(@floatToInt(u32, rand_f64 * @intToFloat(f64, num_buckets)));
342 if (f64_put.found_existing) {
343 f64_put.value_ptr.* += 1;
344 } else {
345 f64_put.value_ptr.* = 0;
346 }
347 }
348
349 var f32_total_variance: f64 = 0;
350 var f64_total_variance: f64 = 0;
351
352 {
353 var j: u32 = 0;
354 while (j < num_buckets) : (j += 1) {
355 const count = @intToFloat(f64, (if (f32_hist.get(j)) |v| v else 0));
356 const expected = @intToFloat(f64, num_numbers) / @intToFloat(f64, num_buckets);
357 const delta = count - expected;
358 const variance = (delta * delta) / expected;
359 f32_total_variance += variance;
360 }
361 }
362
363 {
364 var j: u64 = 0;
365 while (j < num_buckets) : (j += 1) {
366 const count = @intToFloat(f64, (if (f64_hist.get(j)) |v| v else 0));
367 const expected = @intToFloat(f64, num_numbers) / @intToFloat(f64, num_buckets);
368 const delta = count - expected;
369 const variance = (delta * delta) / expected;
370 f64_total_variance += variance;
371 }
372 }
373
374 // Corresponds to a p-value > 0.05.
375 // Critical value is calculated by opening a Python interpreter and running:
376 // scipy.stats.chi2.isf(0.05, num_buckets - 1)
377 const critical_value = 1073.6426506574246;
378 try expect(f32_total_variance < critical_value);
379 try expect(f64_total_variance < critical_value);
380}
381
382test "Random shuffle" {
383 var prng = DefaultPrng.init(0);
384 const random = prng.random();
385
386 var seq = [_]u8{ 0, 1, 2, 3, 4 };
387 var seen = [_]bool{false} ** 5;
388
389 var i: usize = 0;
390 while (i < 1000) : (i += 1) {
391 random.shuffle(u8, seq[0..]);
392 seen[seq[0]] = true;
393 try expect(sumArray(seq[0..]) == 10);
394 }
395
396 // we should see every entry at the head at least once
397 for (seen) |e| {
398 try expect(e == true);
399 }
400}
401
402fn sumArray(s: []const u8) u32 {
403 var r: u32 = 0;
404 for (s) |e|
405 r += e;
406 return r;
407}
408
409test "Random range" {
410 var prng = DefaultPrng.init(0);
411 const random = prng.random();
412
413 try testRange(random, -4, 3);
414 try testRange(random, -4, -1);
415 try testRange(random, 10, 14);
416 try testRange(random, -0x80, 0x7f);
417}
418
419fn testRange(r: Random, start: i8, end: i8) !void {
420 try testRangeBias(r, start, end, true);
421 try testRangeBias(r, start, end, false);
422}
423fn testRangeBias(r: Random, start: i8, end: i8, biased: bool) !void {
424 const count = @intCast(usize, @as(i32, end) - @as(i32, start));
425 var values_buffer = [_]bool{false} ** 0x100;
426 const values = values_buffer[0..count];
427 var i: usize = 0;
428 while (i < count) {
429 const value: i32 = if (biased) r.intRangeLessThanBiased(i8, start, end) else r.intRangeLessThan(i8, start, end);
430 const index = @intCast(usize, value - start);
431 if (!values[index]) {
432 i += 1;
433 values[index] = true;
434 }
435 }
436}
437
438test "CSPRNG" {
439 var secret_seed: [DefaultCsprng.secret_seed_length]u8 = undefined;
440 std.crypto.random.bytes(&secret_seed);
441 var csprng = DefaultCsprng.init(secret_seed);
442 const random = csprng.random();
443 const a = random.int(u64);
444 const b = random.int(u64);
445 const c = random.int(u64);
446 try expect(a ^ b ^ c != 0);
447}