source: doc/theses/colby_parsons_MMath/benchmarks/channels/go/pub_sub/pub_sub.go

package main

import (
        "fmt"
        "sync"
        "time"
        "runtime"
        "os"
        "strconv"
)

var Processors, Tasks int = 1, 1
var BarrierSize int = 2
var done bool = false;
var total_operations uint64 = 0
var m sync.Mutex

var taskJoin chan int = make(chan int, Tasks + 1)

var barWait chan int = make(chan int, 2 * BarrierSize)
var entryWait chan int = make(chan int, 2 * BarrierSize)

func flushBarrier() {
        for j := 0; j < BarrierSize; j++ {
                barWait <- -1
                entryWait <- -1
        }
}

func initBarrier() {
        for j := 0; j < BarrierSize; j++ {
                entryWait <- j
        }
}

func barrier() {
        ticket := <-entryWait
        if ( ticket == -1 ) {
                entryWait <- -1
                return
        }
        if ( ticket == BarrierSize - 1 ) {
                for j := 0; j < BarrierSize - 1; j++ {
                        barWait <- j
                }
        } else {
                ticket = <- barWait
                if ( ticket == -1 ) {
                        barWait <- -1
                        return
                }
        }

        // last one out
        if ( BarrierSize == 1 || ticket == BarrierSize - 2 ) {
                for j := 0; j < BarrierSize; j++ {
                        entryWait <- j
                }
        }
}

func task( chans [] chan uint64 ) {
        var count uint64 = 0
        for {
                if done { break }
                for j := 0; j < Tasks; j++ {
                        chans[j] <- 0
                }

                for j := 0; j < Tasks; j++ {
                        <- chans[j]
                }
                barrier()
                count++
        }
        m.Lock()
        total_operations += count
        // fmt.Print("C: ",count)
        m.Unlock()
        taskJoin <- 0
}

func usage() {
        fmt.Printf( "Usage: %v " +
                "[ processors (> 0) | 'd' (default %v) ] " +
                "[ BarrierSize (> 0) | 'd' (default %v) ]\n",
                os.Args[0], Processors, BarrierSize );
        os.Exit( 1 );
}

func main() {
        switch len( os.Args ) {
                case 3:
                        if os.Args[2] != "d" {                                                  // default ?
                                Tasks, _ = strconv.Atoi( os.Args[2] )
                                if Tasks < 1 { usage(); }
                        } // if
                fallthrough
                case 2:
                        if os.Args[1] != "d" {                                                  // default ?
                                Processors, _ = strconv.Atoi( os.Args[1] )
                                if Processors < 1 { usage(); }
                        } // if
                case 1:                                                                                 // use defaults
                default:
                usage();
        } // switch
        runtime.GOMAXPROCS( Processors );
        Tasks = Processors
        BarrierSize = Tasks

        // fmt.Println("Processors: ",Processors," Channels: ",Channels," ProdsPerChan: ",ProdsPerChan," ConsPerChan: ",ConsPerChan," Channel Size: ",ChannelSize)
        taskJoin = make(chan int, Tasks + 1)
        barWait = make(chan int, 2 * BarrierSize)
        entryWait = make(chan int, 2 * BarrierSize)
        initBarrier()

        chans := make( [] chan uint64, Tasks )
        for i := range chans {
                chans[i] = make(chan uint64, 2 * Tasks)
        }

        for j := 0; j < Tasks; j++ {
                go task( chans )
        }
                
        // wait 10 seconds
        time.Sleep(time.Second * 10)
        // fmt.Println("prod done\n")
        done = true

        for i := 0; i < Tasks; i++ {
                for j := 0; j < Tasks; j++ {
                        chans[i] <- 0
                }
        }

        flushBarrier()
        
        for j := 0; j < Tasks; j++ {
                <-taskJoin
        }

    fmt.Println(total_operations)
}