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 // +build ignore 6 7 // This program computes the value of rng_cooked 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
