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Commit f9e404c1 authored by Spencer Nelson's avatar Spencer Nelson Committed by Rob Pike
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math/rand: make Rand fulfill the Reader interface 

Add a Read function to Rand which reads random bytes into a buffer.

Fixes #8330

Change-Id: I85b90277b8be9287c6697def8dbefe0029b6ee06
Reviewed-on: https://go-review.googlesource.com/14522Reviewed-by: 's avatarRob Pike <r@golang.org>
parent 2421c6e3
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Showing with 150 additions and 24 deletions
src/math/rand/rand.go
View file @ f9e404c1
......@@ -156,6 +156,19 @@ func (r *Rand) Perm(n int) []int {
return m
}
// Read generates len(p) random bytes and writes them into p. It
// always returns len(p) and a nil error.
func (r *Rand) Read(p []byte) (n int, err error) {
for i := 0; i < len(p); i += 7 {
val := r.src.Int63()
for j := 0; i+j < len(p) && j < 7; j++ {
p[i+j] = byte(val)
val >>= 8
}
}
return len(p), nil
}
/*
* Top-level convenience functions
*/
......@@ -209,6 +222,10 @@ func Float32() float32 { return globalRand.Float32() }
// from the default Source.
func Perm(n int) []int { return globalRand.Perm(n) }
// Read generates len(p) random bytes from the default Source and
// writes them into p. It always returns len(p) and a nil error.
func Read(p []byte) (n int, err error) { return globalRand.Read(p) }
// NormFloat64 returns a normally distributed float64 in the range
// [-math.MaxFloat64, +math.MaxFloat64] with
// standard normal distribution (mean = 0, stddev = 1)
......
src/math/rand/rand_test.go
View file @ f9e404c1
......@@ -342,6 +342,59 @@ func TestFloat32(t *testing.T) {
}
}
func testReadUniformity(t *testing.T, n int, seed int64) {
r := New(NewSource(seed))
buf := make([]byte, n)
nRead, err := r.Read(buf)
if err != nil {
t.Errorf("Read err %v", err)
}
if nRead != n {
t.Errorf("Read returned unexpected n; %d != %d", nRead, n)
}
// Expect a uniform distribution of byte values, which lie in [0, 255].
var (
mean = 255.0 / 2
stddev = math.Sqrt(255.0 * 255.0 / 12.0)
errorScale = stddev / math.Sqrt(float64(n))
)
expected := &statsResults{mean, stddev, 0.10 * errorScale, 0.08 * errorScale}
// Cast bytes as floats to use the common distribution-validity checks.
samples := make([]float64, n)
for i, val := range buf {
samples[i] = float64(val)
}
// Make sure that the entire set matches the expected distribution.
checkSampleDistribution(t, samples, expected)
}
func TestRead(t *testing.T) {
testBufferSizes := []int{
2, 4, 7, 64, 1024, 1 << 16, 1 << 20,
}
for _, seed := range testSeeds {
for _, n := range testBufferSizes {
testReadUniformity(t, n, seed)
}
}
}
func TestReadEmpty(t *testing.T) {
r := New(NewSource(1))
buf := make([]byte, 0)
n, err := r.Read(buf)
if err != nil {
t.Errorf("Read err into empty buffer; %v", err)
}
if n != 0 {
t.Errorf("Read into empty buffer returned unexpected n of %d", n)
}
}
// Benchmarks
func BenchmarkInt63Threadsafe(b *testing.B) {
......@@ -405,3 +458,30 @@ func BenchmarkPerm30(b *testing.B) {
r.Perm(30)
}
}
func BenchmarkRead3(b *testing.B) {
r := New(NewSource(1))
buf := make([]byte, 3)
b.ResetTimer()
for n := b.N; n > 0; n-- {
r.Read(buf)
}
}
func BenchmarkRead64(b *testing.B) {
r := New(NewSource(1))
buf := make([]byte, 64)
b.ResetTimer()
for n := b.N; n > 0; n-- {
r.Read(buf)
}
}
func BenchmarkRead1000(b *testing.B) {
r := New(NewSource(1))
buf := make([]byte, 1000)
b.ResetTimer()
for n := b.N; n > 0; n-- {
r.Read(buf)
}
}
src/math/rand/regress_test.go
View file @ f9e404c1
......@@ -25,6 +25,7 @@ func TestRegress(t *testing.T) {
var int32s = []int32{1, 10, 32, 1 << 20, 1<<20 + 1, 1000000000, 1 << 30, 1<<31 - 2, 1<<31 - 1}
var int64s = []int64{1, 10, 32, 1 << 20, 1<<20 + 1, 1000000000, 1 << 30, 1<<31 - 2, 1<<31 - 1, 1000000000000000000, 1 << 60, 1<<63 - 2, 1<<63 - 1}
var permSizes = []int{0, 1, 5, 8, 9, 10, 16}
var readBufferSizes = []int{1, 7, 8, 9, 10}
r := New(NewSource(0))
rv := reflect.ValueOf(r)
......@@ -40,9 +41,6 @@ func TestRegress(t *testing.T) {
if mt.NumOut() == 0 {
continue
}
if mt.NumOut() != 1 {
t.Fatalf("unexpected result count for r.%s", m.Name)
}
r.Seed(0)
for repeat := 0; repeat < 20; repeat++ {
var args []reflect.Value
......@@ -74,14 +72,25 @@ func TestRegress(t *testing.T) {
case reflect.Int64:
x = int64s[repeat%len(int64s)]
case reflect.Slice:
if m.Name == "Read" {
n := readBufferSizes[repeat%len(readBufferSizes)]
x = make([]byte, n)
}
}
argstr = fmt.Sprint(x)
args = append(args, reflect.ValueOf(x))
}
out := mv.Call(args)[0].Interface()
var out interface{}
out = mv.Call(args)[0].Interface()
if m.Name == "Int" || m.Name == "Intn" {
out = int64(out.(int))
}
if m.Name == "Read" {
out = args[0].Interface().([]byte)
}
if *printgolden {
var val string
big := int64(1 << 60)
......@@ -332,24 +341,44 @@ var regressGolden = []interface{}{
[]int{2, 1, 7, 0, 6, 3, 4, 5}, // Perm(8)
[]int{8, 7, 5, 3, 4, 6, 0, 1, 2}, // Perm(9)
[]int{1, 0, 2, 5, 7, 6, 9, 8, 3, 4}, // Perm(10)
uint32(4059586549), // Uint32()
uint32(1052117029), // Uint32()
uint32(2817310706), // Uint32()
uint32(233405013), // Uint32()
uint32(1578775030), // Uint32()
uint32(1243308993), // Uint32()
uint32(826517535), // Uint32()
uint32(2814630155), // Uint32()
uint32(3853314576), // Uint32()
uint32(718781857), // Uint32()
uint32(1239465936), // Uint32()
uint32(3876658295), // Uint32()
uint32(3649778518), // Uint32()
uint32(1172727096), // Uint32()
uint32(2615979505), // Uint32()
uint32(1089444252), // Uint32()
uint32(3327114623), // Uint32()
uint32(75079301), // Uint32()
uint32(3380456901), // Uint32()
uint32(3433369789), // Uint32()
[]byte{0x1}, // Read([0])
[]byte{0xc0, 0x41, 0xd3, 0xff, 0x12, 0x4, 0x5b}, // Read([0 0 0 0 0 0 0])
[]byte{0x73, 0xc8, 0x6e, 0x4f, 0xf9, 0x5f, 0xf6, 0x62}, // Read([0 0 0 0 0 0 0 0])
[]byte{0x4a, 0x2d, 0xb, 0x75, 0xfb, 0x18, 0xd, 0xaf, 0x48}, // Read([0 0 0 0 0 0 0 0 0])
[]byte{0x39, 0x46, 0x51, 0x85, 0xf, 0xd4, 0xa1, 0x78, 0x89, 0x2e}, // Read([0 0 0 0 0 0 0 0 0 0])
[]byte{0x51}, // Read([0])
[]byte{0x4e, 0xe2, 0xd3, 0xd0, 0xd0, 0xde, 0x6b}, // Read([0 0 0 0 0 0 0])
[]byte{0xf8, 0xf9, 0xb4, 0x4c, 0xe8, 0x5f, 0xf0, 0x44}, // Read([0 0 0 0 0 0 0 0])
[]byte{0x3b, 0xbf, 0x85, 0x7a, 0xab, 0x99, 0xc5, 0xb2, 0x52}, // Read([0 0 0 0 0 0 0 0 0])
[]byte{0xa8, 0xae, 0xb7, 0x9e, 0xf8, 0x56, 0xf6, 0x59, 0xc1, 0x8f}, // Read([0 0 0 0 0 0 0 0 0 0])
[]byte{0xc7}, // Read([0])
[]byte{0x5f, 0x67, 0xcf, 0xe2, 0x42, 0xcf, 0x3c}, // Read([0 0 0 0 0 0 0])
[]byte{0xc3, 0x54, 0xf3, 0xed, 0xe2, 0xd6, 0xbe, 0xcc}, // Read([0 0 0 0 0 0 0 0])
[]byte{0x6a, 0x9f, 0x4a, 0x57, 0x8b, 0xcb, 0x9e, 0xf2, 0xd4}, // Read([0 0 0 0 0 0 0 0 0])
[]byte{0x6d, 0x29, 0x97, 0x61, 0xea, 0x9e, 0x4f, 0x5a, 0xa6, 0xae}, // Read([0 0 0 0 0 0 0 0 0 0])
[]byte{0xaa}, // Read([0])
[]byte{0x20, 0xef, 0xcd, 0x6c, 0xea, 0x84, 0xb6}, // Read([0 0 0 0 0 0 0])
[]byte{0x92, 0x5e, 0x60, 0x7b, 0xe0, 0x63, 0x71, 0x6f}, // Read([0 0 0 0 0 0 0 0])
[]byte{0x4, 0x5c, 0x3f, 0x0, 0xf, 0x8a, 0x79, 0x6b, 0xce}, // Read([0 0 0 0 0 0 0 0 0])
[]byte{0xaa, 0xca, 0xee, 0xdf, 0xad, 0x5b, 0x50, 0x66, 0x64, 0xe8}, // Read([0 0 0 0 0 0 0 0 0 0])
uint32(4059586549), // Uint32()
uint32(1052117029), // Uint32()
uint32(2817310706), // Uint32()
uint32(233405013), // Uint32()
uint32(1578775030), // Uint32()
uint32(1243308993), // Uint32()
uint32(826517535), // Uint32()
uint32(2814630155), // Uint32()
uint32(3853314576), // Uint32()
uint32(718781857), // Uint32()
uint32(1239465936), // Uint32()
uint32(3876658295), // Uint32()
uint32(3649778518), // Uint32()
uint32(1172727096), // Uint32()
uint32(2615979505), // Uint32()
uint32(1089444252), // Uint32()
uint32(3327114623), // Uint32()
uint32(75079301), // Uint32()
uint32(3380456901), // Uint32()
uint32(3433369789), // Uint32()
}
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