# Golang使用扇入法寻找素数

FredricZhu · · 687 次点击 · · 开始浏览

pips/pip_prime.go

``````package pips

import (
"sync"
)

type PrimePip struct {
}

func NewPrimePip() *PrimePip {
primePip := &PrimePip{}
return primePip
}

func (primePip *PrimePip) RepeatFn(
done <-chan interface{},
fn func() interface{},
) <-chan interface{} {
valueStream := make(chan interface{})
go func() {
defer close(valueStream)
for {
select {
case <-done:
return
case valueStream <- fn():
}
}
}()
return valueStream
}

func (primePip *PrimePip) Take(
done <-chan interface{},
valueStream <-chan interface{},
num int,
) <-chan interface{} {
takeStream := make(chan interface{})
go func() {
defer close(takeStream)
for i := 0; i < num; i++ {
select {
case <-done:
return
case takeStream <- <-valueStream:
}
}
}()
return takeStream
}

func (primePip *PrimePip) ToInt(
done <-chan interface{},
valueStream <-chan interface{},
) <-chan int {
intStream := make(chan int)
go func() {
defer close(intStream)
for v := range valueStream {
select {
case <-done:
return
case intStream <- v.(int):
}
}
}()
return intStream
}

func (primePip *PrimePip) PrimeFinder(
done <-chan interface{},
intStream <-chan int,
) <-chan interface{} {
primeStream := make(chan interface{})
go func() {
defer close(primeStream)
for integer := range intStream {
integer -= 1
prime := true
for divisor := integer - 1; divisor > 1; divisor-- {
if integer%divisor == 0 {
prime = false
break
}
}

if prime {
select {
case <-done:
return
case primeStream <- integer:
}
}
}
}()
return primeStream
}

func (primePip *PrimePip) FanIn(
done <-chan interface{},
channels ...<-chan interface{},
) <-chan interface{} {
var wg sync.WaitGroup
multiplexedStream := make(chan interface{})

multiplexed := func(c <-chan interface{}) {
defer wg.Done()
for i := range c {
select {
case <-done:
return
case multiplexedStream <- i:
}
}
}

for _, c := range channels {
go multiplexed(c)
}

go func() {
wg.Wait()
close(multiplexedStream)
}()

return multiplexedStream
}
``````

fanin2.go

``````// fanin2
package main

import (
"fanin2/pips"
"fmt"
"math/rand"
"runtime"
"time"
)

func main() {
done := make(chan interface{})
defer close(done)
start := time.Now()
rand := func() interface{} {
return rand.Intn(50000000)
}

primeP := pips.NewPrimePip()
randIntStream := primeP.ToInt(done, primeP.RepeatFn(done, rand))
numFinders := runtime.NumCPU()
fmt.Printf("Spinning up %d prime Finders \n", numFinders)
finders := make([]<-chan interface{}, numFinders)

fmt.Println("Primes:")
for i := 0; i < numFinders; i++ {
finders[i] = primeP.PrimeFinder(done, randIntStream)
}

for prime := range primeP.Take(done, primeP.FanIn(done, finders...), 10) {
fmt.Printf("\t%d \n", prime)
}

fmt.Printf("Search Took: %v \n", time.Since(start))
}
``````

image.png

0 回复

• 请尽量让自己的回复能够对别人有帮助
• 支持 Markdown 格式, **粗体**、~~删除线~~、``单行代码``
• 支持 @ 本站用户；支持表情（输入 : 提示），见 Emoji cheat sheet
• 图片支持拖拽、截图粘贴等方式上传

pips/pip_prime.go

``````package pips

import (
"sync"
)

type PrimePip struct {
}

func NewPrimePip() *PrimePip {
primePip := &PrimePip{}
return primePip
}

func (primePip *PrimePip) RepeatFn(
done <-chan interface{},
fn func() interface{},
) <-chan interface{} {
valueStream := make(chan interface{})
go func() {
defer close(valueStream)
for {
select {
case <-done:
return
case valueStream <- fn():
}
}
}()
return valueStream
}

func (primePip *PrimePip) Take(
done <-chan interface{},
valueStream <-chan interface{},
num int,
) <-chan interface{} {
takeStream := make(chan interface{})
go func() {
defer close(takeStream)
for i := 0; i < num; i++ {
select {
case <-done:
return
case takeStream <- <-valueStream:
}
}
}()
return takeStream
}

func (primePip *PrimePip) ToInt(
done <-chan interface{},
valueStream <-chan interface{},
) <-chan int {
intStream := make(chan int)
go func() {
defer close(intStream)
for v := range valueStream {
select {
case <-done:
return
case intStream <- v.(int):
}
}
}()
return intStream
}

func (primePip *PrimePip) PrimeFinder(
done <-chan interface{},
intStream <-chan int,
) <-chan interface{} {
primeStream := make(chan interface{})
go func() {
defer close(primeStream)
for integer := range intStream {
integer -= 1
prime := true
for divisor := integer - 1; divisor > 1; divisor-- {
if integer%divisor == 0 {
prime = false
break
}
}

if prime {
select {
case <-done:
return
case primeStream <- integer:
}
}
}
}()
return primeStream
}

func (primePip *PrimePip) FanIn(
done <-chan interface{},
channels ...<-chan interface{},
) <-chan interface{} {
var wg sync.WaitGroup
multiplexedStream := make(chan interface{})

multiplexed := func(c <-chan interface{}) {
defer wg.Done()
for i := range c {
select {
case <-done:
return
case multiplexedStream <- i:
}
}
}

for _, c := range channels {
go multiplexed(c)
}

go func() {
wg.Wait()
close(multiplexedStream)
}()

return multiplexedStream
}
``````

fanin2.go

``````// fanin2
package main

import (
"fanin2/pips"
"fmt"
"math/rand"
"runtime"
"time"
)

func main() {
done := make(chan interface{})
defer close(done)
start := time.Now()
rand := func() interface{} {
return rand.Intn(50000000)
}

primeP := pips.NewPrimePip()
randIntStream := primeP.ToInt(done, primeP.RepeatFn(done, rand))
numFinders := runtime.NumCPU()
fmt.Printf("Spinning up %d prime Finders \n", numFinders)
finders := make([]<-chan interface{}, numFinders)

fmt.Println("Primes:")
for i := 0; i < numFinders; i++ {
finders[i] = primeP.PrimeFinder(done, randIntStream)
}

for prime := range primeP.Take(done, primeP.FanIn(done, finders...), 10) {
fmt.Printf("\t%d \n", prime)
}

fmt.Printf("Search Took: %v \n", time.Since(start))
}
``````

image.png