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// 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)
}
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