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.
4 5 //go:build ignore
6 7 // This program computes the value of rngCooked in rng.go,
8 // which is used for seeding all instances of rand.Source.
9 // a 64bit and a 63bit version of the array is printed to
10 // the standard output.
11 12 package main
13 14 import "fmt"
15 16 const (
17 length = 607
18 tap = 273
19 mask = (1 << 63) - 1
20 a = 48271
21 m = (1 << 31) - 1
22 q = 44488
23 r = 3399
24 )
25 26 var (
27 rngVec [length]int64
28 rngTap, rngFeed int
29 )
30 31 func seedrand(x int32) int32 {
32 hi := x / q
33 lo := x % q
34 x = a*lo - r*hi
35 if x < 0 {
36 x += m
37 }
38 return x
39 }
40 41 func srand(seed int32) {
42 rngTap = 0
43 rngFeed = length - tap
44 seed %= m
45 if seed < 0 {
46 seed += m
47 } else if seed == 0 {
48 seed = 89482311
49 }
50 x := seed
51 for i := -20; i < length; i++ {
52 x = seedrand(x)
53 if i >= 0 {
54 var u int64
55 u = int64(x) << 20
56 x = seedrand(x)
57 u ^= int64(x) << 10
58 x = seedrand(x)
59 u ^= int64(x)
60 rngVec[i] = u
61 }
62 }
63 }
64 65 func vrand() int64 {
66 rngTap--
67 if rngTap < 0 {
68 rngTap += length
69 }
70 rngFeed--
71 if rngFeed < 0 {
72 rngFeed += length
73 }
74 x := (rngVec[rngFeed] + rngVec[rngTap])
75 rngVec[rngFeed] = x
76 return x
77 }
78 79 func main() {
80 srand(1)
81 for i := uint64(0); i < 7.8e12; i++ {
82 vrand()
83 }
84 fmt.Printf("rngVec after 7.8e12 calls to vrand:\n%#v\n", rngVec)
85 for i := range rngVec {
86 rngVec[i] &= mask
87 }
88 fmt.Printf("lower 63bit of rngVec after 7.8e12 calls to vrand:\n%#v\n", rngVec)
89 }
90