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