| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // +build ignore |
| |
| // This program computes the value of rngCooked in rng.go, |
| // which is used for seeding all instances of rand.Source. |
| // a 64bit and a 63bit version of the array is printed to |
| // the standard output. |
| |
| package main |
| |
| import "fmt" |
| |
| const ( |
| length = 607 |
| tap = 273 |
| mask = (1 << 63) - 1 |
| a = 48271 |
| m = (1 << 31) - 1 |
| q = 44488 |
| r = 3399 |
| ) |
| |
| var ( |
| rngVec [length]int64 |
| rngTap, rngFeed int |
| ) |
| |
| func seedrand(x int32) int32 { |
| hi := x / q |
| lo := x % q |
| x = a*lo - r*hi |
| if x < 0 { |
| x += m |
| } |
| return x |
| } |
| |
| func srand(seed int32) { |
| rngTap = 0 |
| rngFeed = length - tap |
| seed %= m |
| if seed < 0 { |
| seed += m |
| } else if seed == 0 { |
| seed = 89482311 |
| } |
| x := seed |
| for i := -20; i < length; i++ { |
| x = seedrand(x) |
| if i >= 0 { |
| var u int64 |
| u = int64(x) << 20 |
| x = seedrand(x) |
| u ^= int64(x) << 10 |
| x = seedrand(x) |
| u ^= int64(x) |
| rngVec[i] = u |
| } |
| } |
| } |
| |
| func vrand() int64 { |
| rngTap-- |
| if rngTap < 0 { |
| rngTap += length |
| } |
| rngFeed-- |
| if rngFeed < 0 { |
| rngFeed += length |
| } |
| x := (rngVec[rngFeed] + rngVec[rngTap]) |
| rngVec[rngFeed] = x |
| return x |
| } |
| |
| func main() { |
| srand(1) |
| for i := uint64(0); i < 7.8e12; i++ { |
| vrand() |
| } |
| fmt.Printf("rngVec after 7.8e12 calls to vrand:\n%#v\n", rngVec) |
| for i := range rngVec { |
| rngVec[i] &= mask |
| } |
| fmt.Printf("lower 63bit of rngVec after 7.8e12 calls to vrand:\n%#v\n", rngVec) |
| } |