1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
20 numTestSamples = 10000
23 var rn, kn, wn, fn = GetNormalDistributionParameters()
24 var re, ke, we, fe = GetExponentialDistributionParameters()
26 type statsResults struct {
33 func max(a, b float64) float64 {
40 func nearEqual(a, b, closeEnough, maxError float64) bool {
41 absDiff := math.Abs(a - b)
42 if absDiff < closeEnough { // Necessary when one value is zero and one value is close to zero.
45 return absDiff/max(math.Abs(a), math.Abs(b)) < maxError
48 var testSeeds = []int64{1, 1754801282, 1698661970, 1550503961}
50 // checkSimilarDistribution returns success if the mean and stddev of the
51 // two statsResults are similar.
52 func (this *statsResults) checkSimilarDistribution(expected *statsResults) error {
53 if !nearEqual(this.mean, expected.mean, expected.closeEnough, expected.maxError) {
54 s := fmt.Sprintf("mean %v != %v (allowed error %v, %v)", this.mean, expected.mean, expected.closeEnough, expected.maxError)
58 if !nearEqual(this.stddev, expected.stddev, expected.closeEnough, expected.maxError) {
59 s := fmt.Sprintf("stddev %v != %v (allowed error %v, %v)", this.stddev, expected.stddev, expected.closeEnough, expected.maxError)
66 func getStatsResults(samples []float64) *statsResults {
67 res := new(statsResults)
68 var sum, squaresum float64
69 for _, s := range samples {
73 res.mean = sum / float64(len(samples))
74 res.stddev = math.Sqrt(squaresum/float64(len(samples)) - res.mean*res.mean)
78 func checkSampleDistribution(t *testing.T, samples []float64, expected *statsResults) {
80 actual := getStatsResults(samples)
81 err := actual.checkSimilarDistribution(expected)
87 func checkSampleSliceDistributions(t *testing.T, samples []float64, nslices int, expected *statsResults) {
89 chunk := len(samples) / nslices
90 for i := 0; i < nslices; i++ {
94 high = len(samples) - 1
96 high = (i + 1) * chunk
98 checkSampleDistribution(t, samples[low:high], expected)
103 // Normal distribution tests
106 func generateNormalSamples(nsamples int, mean, stddev float64, seed int64) []float64 {
107 r := New(NewSource(seed))
108 samples := make([]float64, nsamples)
109 for i := range samples {
110 samples[i] = r.NormFloat64()*stddev + mean
115 func testNormalDistribution(t *testing.T, nsamples int, mean, stddev float64, seed int64) {
116 //fmt.Printf("testing nsamples=%v mean=%v stddev=%v seed=%v\n", nsamples, mean, stddev, seed);
118 samples := generateNormalSamples(nsamples, mean, stddev, seed)
119 errorScale := max(1.0, stddev) // Error scales with stddev
120 expected := &statsResults{mean, stddev, 0.10 * errorScale, 0.08 * errorScale}
122 // Make sure that the entire set matches the expected distribution.
123 checkSampleDistribution(t, samples, expected)
125 // Make sure that each half of the set matches the expected distribution.
126 checkSampleSliceDistributions(t, samples, 2, expected)
128 // Make sure that each 7th of the set matches the expected distribution.
129 checkSampleSliceDistributions(t, samples, 7, expected)
134 func TestStandardNormalValues(t *testing.T) {
135 for _, seed := range testSeeds {
136 testNormalDistribution(t, numTestSamples, 0, 1, seed)
140 func TestNonStandardNormalValues(t *testing.T) {
147 for sd := 0.5; sd < sdmax; sd *= 2 {
148 for m := 0.5; m < mmax; m *= 2 {
149 for _, seed := range testSeeds {
150 testNormalDistribution(t, numTestSamples, m, sd, seed)
160 // Exponential distribution tests
163 func generateExponentialSamples(nsamples int, rate float64, seed int64) []float64 {
164 r := New(NewSource(seed))
165 samples := make([]float64, nsamples)
166 for i := range samples {
167 samples[i] = r.ExpFloat64() / rate
172 func testExponentialDistribution(t *testing.T, nsamples int, rate float64, seed int64) {
173 //fmt.Printf("testing nsamples=%v rate=%v seed=%v\n", nsamples, rate, seed);
178 samples := generateExponentialSamples(nsamples, rate, seed)
179 errorScale := max(1.0, 1/rate) // Error scales with the inverse of the rate
180 expected := &statsResults{mean, stddev, 0.10 * errorScale, 0.20 * errorScale}
182 // Make sure that the entire set matches the expected distribution.
183 checkSampleDistribution(t, samples, expected)
185 // Make sure that each half of the set matches the expected distribution.
186 checkSampleSliceDistributions(t, samples, 2, expected)
188 // Make sure that each 7th of the set matches the expected distribution.
189 checkSampleSliceDistributions(t, samples, 7, expected)
194 func TestStandardExponentialValues(t *testing.T) {
195 for _, seed := range testSeeds {
196 testExponentialDistribution(t, numTestSamples, 1, seed)
200 func TestNonStandardExponentialValues(t *testing.T) {
201 for rate := 0.05; rate < 10; rate *= 2 {
202 for _, seed := range testSeeds {
203 testExponentialDistribution(t, numTestSamples, rate, seed)
212 // Table generation tests
215 func initNorm() (testKn []uint32, testWn, testFn []float32) {
220 vn float64 = 9.91256303526217e-3
223 testKn = make([]uint32, 128)
224 testWn = make([]float32, 128)
225 testFn = make([]float32, 128)
227 q := vn / math.Exp(-0.5*dn*dn)
228 testKn[0] = uint32((dn / q) * m1)
230 testWn[0] = float32(q / m1)
231 testWn[127] = float32(dn / m1)
233 testFn[127] = float32(math.Exp(-0.5 * dn * dn))
234 for i := 126; i >= 1; i-- {
235 dn = math.Sqrt(-2.0 * math.Log(vn/dn+math.Exp(-0.5*dn*dn)))
236 testKn[i+1] = uint32((dn / tn) * m1)
238 testFn[i] = float32(math.Exp(-0.5 * dn * dn))
239 testWn[i] = float32(dn / m1)
244 func initExp() (testKe []uint32, testWe, testFe []float32) {
249 ve float64 = 3.9496598225815571993e-3
252 testKe = make([]uint32, 256)
253 testWe = make([]float32, 256)
254 testFe = make([]float32, 256)
256 q := ve / math.Exp(-de)
257 testKe[0] = uint32((de / q) * m2)
259 testWe[0] = float32(q / m2)
260 testWe[255] = float32(de / m2)
262 testFe[255] = float32(math.Exp(-de))
263 for i := 254; i >= 1; i-- {
264 de = -math.Log(ve/de + math.Exp(-de))
265 testKe[i+1] = uint32((de / te) * m2)
267 testFe[i] = float32(math.Exp(-de))
268 testWe[i] = float32(de / m2)
273 // compareUint32Slices returns the first index where the two slices
274 // disagree, or <0 if the lengths are the same and all elements
276 func compareUint32Slices(s1, s2 []uint32) int {
277 if len(s1) != len(s2) {
278 if len(s1) > len(s2) {
291 // compareFloat32Slices returns the first index where the two slices
292 // disagree, or <0 if the lengths are the same and all elements
294 func compareFloat32Slices(s1, s2 []float32) int {
295 if len(s1) != len(s2) {
296 if len(s1) > len(s2) {
302 if !nearEqual(float64(s1[i]), float64(s2[i]), 0, 1e-7) {
309 func TestNormTables(t *testing.T) {
310 testKn, testWn, testFn := initNorm()
311 if i := compareUint32Slices(kn[0:], testKn); i >= 0 {
312 t.Errorf("kn disagrees at index %v; %v != %v", i, kn[i], testKn[i])
314 if i := compareFloat32Slices(wn[0:], testWn); i >= 0 {
315 t.Errorf("wn disagrees at index %v; %v != %v", i, wn[i], testWn[i])
317 if i := compareFloat32Slices(fn[0:], testFn); i >= 0 {
318 t.Errorf("fn disagrees at index %v; %v != %v", i, fn[i], testFn[i])
322 func TestExpTables(t *testing.T) {
323 testKe, testWe, testFe := initExp()
324 if i := compareUint32Slices(ke[0:], testKe); i >= 0 {
325 t.Errorf("ke disagrees at index %v; %v != %v", i, ke[i], testKe[i])
327 if i := compareFloat32Slices(we[0:], testWe); i >= 0 {
328 t.Errorf("we disagrees at index %v; %v != %v", i, we[i], testWe[i])
330 if i := compareFloat32Slices(fe[0:], testFe); i >= 0 {
331 t.Errorf("fe disagrees at index %v; %v != %v", i, fe[i], testFe[i])
335 func hasSlowFloatingPoint() bool {
336 switch runtime.GOARCH {
338 return os.Getenv("GOARM") == "5"
339 case "mips", "mipsle", "mips64", "mips64le":
340 // Be conservative and assume that all mips boards
341 // have emulated floating point.
342 // TODO: detect what it actually has.
348 func TestFloat32(t *testing.T) {
349 // For issue 6721, the problem came after 7533753 calls, so check 10e6.
351 // But do the full amount only on builders (not locally).
352 // But ARM5 floating point emulation is slow (Issue 10749), so
353 // do less for that builder:
354 if testing.Short() && (testenv.Builder() == "" || hasSlowFloatingPoint()) {
355 num /= 100 // 1.72 seconds instead of 172 seconds
358 r := New(NewSource(1))
359 for ct := 0; ct < num; ct++ {
362 t.Fatal("Float32() should be in range [0,1). ct:", ct, "f:", f)
367 func TestShuffleSmall(t *testing.T) {
368 // Check that Shuffle allows n=0 and n=1, but that swap is never called for them.
369 r := New(NewSource(1))
370 for n := 0; n <= 1; n++ {
371 r.Shuffle(n, func(i, j int) { t.Fatalf("swap called, n=%d i=%d j=%d", n, i, j) })
375 // encodePerm converts from a permuted slice of length n, such as Perm generates, to an int in [0, n!).
376 // See https://en.wikipedia.org/wiki/Lehmer_code.
377 // encodePerm modifies the input slice.
378 func encodePerm(s []int) int {
379 // Convert to Lehmer code.
380 for i, x := range s {
382 for j, y := range r {
388 // Convert to int in [0, n!).
391 for i := len(s) - 1; i >= 0; i-- {
398 // TestUniformFactorial tests several ways of generating a uniform value in [0, n!).
399 func TestUniformFactorial(t *testing.T) {
400 r := New(NewSource(testSeeds[0]))
405 for n := 3; n <= top; n++ {
406 t.Run(fmt.Sprintf("n=%d", n), func(t *testing.T) {
409 for i := 2; i <= n; i++ {
413 // Test a few different ways to generate a uniform distribution.
414 p := make([]int, n) // re-usable slice for Shuffle generator
415 tests := [...]struct {
419 {name: "Int32N", fn: func() int { return int(r.Int32N(int32(nfact))) }},
420 {name: "int31n", fn: func() int { return int(Int32NForTest(r, int32(nfact))) }},
421 {name: "Perm", fn: func() int { return encodePerm(r.Perm(n)) }},
422 {name: "Shuffle", fn: func() int {
423 // Generate permutation using Shuffle.
427 r.Shuffle(n, func(i, j int) { p[i], p[j] = p[j], p[i] })
432 for _, test := range tests {
433 t.Run(test.name, func(t *testing.T) {
434 // Gather chi-squared values and check that they follow
435 // the expected normal distribution given n!-1 degrees of freedom.
436 // See https://en.wikipedia.org/wiki/Pearson%27s_chi-squared_test and
437 // https://www.johndcook.com/Beautiful_Testing_ch10.pdf.
438 nsamples := 10 * nfact
442 samples := make([]float64, nsamples)
443 for i := range samples {
444 // Generate some uniformly distributed values and count their occurrences.
446 counts := make([]int, nfact)
447 for i := 0; i < iters; i++ {
450 // Calculate chi-squared and add to samples.
451 want := iters / float64(nfact)
453 for _, have := range counts {
454 err := float64(have) - want
461 // Check that our samples approximate the appropriate normal distribution.
462 dof := float64(nfact - 1)
463 expected := &statsResults{mean: dof, stddev: math.Sqrt(2 * dof)}
464 errorScale := max(1.0, expected.stddev)
465 expected.closeEnough = 0.10 * errorScale
466 expected.maxError = 0.08 // TODO: What is the right value here? See issue 21211.
467 checkSampleDistribution(t, samples, expected)
476 func BenchmarkInt64Threadsafe(b *testing.B) {
477 for n := b.N; n > 0; n-- {
482 func BenchmarkInt64ThreadsafeParallel(b *testing.B) {
483 b.RunParallel(func(pb *testing.PB) {
490 func BenchmarkInt64Unthreadsafe(b *testing.B) {
491 r := New(NewSource(1))
492 for n := b.N; n > 0; n-- {
497 func BenchmarkIntN1000(b *testing.B) {
498 r := New(NewSource(1))
499 for n := b.N; n > 0; n-- {
504 func BenchmarkInt64N1000(b *testing.B) {
505 r := New(NewSource(1))
506 for n := b.N; n > 0; n-- {
511 func BenchmarkInt32N1000(b *testing.B) {
512 r := New(NewSource(1))
513 for n := b.N; n > 0; n-- {
518 func BenchmarkFloat32(b *testing.B) {
519 r := New(NewSource(1))
520 for n := b.N; n > 0; n-- {
525 func BenchmarkFloat64(b *testing.B) {
526 r := New(NewSource(1))
527 for n := b.N; n > 0; n-- {
532 func BenchmarkPerm3(b *testing.B) {
533 r := New(NewSource(1))
534 for n := b.N; n > 0; n-- {
539 func BenchmarkPerm30(b *testing.B) {
540 r := New(NewSource(1))
541 for n := b.N; n > 0; n-- {
546 func BenchmarkPerm30ViaShuffle(b *testing.B) {
547 r := New(NewSource(1))
548 for n := b.N; n > 0; n-- {
553 r.Shuffle(30, func(i, j int) { p[i], p[j] = p[j], p[i] })
557 // BenchmarkShuffleOverhead uses a minimal swap function
558 // to measure just the shuffling overhead.
559 func BenchmarkShuffleOverhead(b *testing.B) {
560 r := New(NewSource(1))
561 for n := b.N; n > 0; n-- {
562 r.Shuffle(52, func(i, j int) {
563 if i < 0 || i >= 52 || j < 0 || j >= 52 {
564 b.Fatalf("bad swap(%d, %d)", i, j)
570 func BenchmarkConcurrent(b *testing.B) {
572 var wg sync.WaitGroup
574 for i := 0; i < goroutines; i++ {
577 for n := b.N; n > 0; n-- {