concurrentprime.go

package main

import (
    "fmt"
    "runtime"
)

// Tune me!
const batchSize = 5000

func main() {

    // Tune me!
    runtime.GOMAXPROCS(runtime.NumCPU())

    primes := make(chan uint32)
    jobs := make(chan uint32)

    fmt.Println("1")
    fmt.Println("2")

    // Tune me!
    numJobs := runtime.NumCPU()

    for i := 0; i < numJobs; i++ {
        go func() {
            for x := range jobs {
            next:
                for end := x + batchSize; x < end; x += 2 {
                    if x%2 == 0 {
                        continue
                    }
                    for j := uint32(3); j < x; j += 2 {
                        if x%j == 0 {
                            continue next
                        }
                    }
                    primes <- x
                }
            }
        }()
    }
    highest := uint32(2)

    go func() {
        for i := uint32(3); ; i += batchSize {
            jobs <- i
        }
    }()

    for prime := range primes {
        if prime > highest {
            highest = prime
            fmt.Printf("%d\n", prime)
        }
    }
}