source: doc/theses/colby_parsons_MMAth/benchmarks/waituntil/go/spin4/spin.go

package main

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

var Processors, Channels, Prods, Cons, ChannelSize int = 2, 4, 1, 1, 10
var cons_done, prod_done bool = false, false;
var total_operations uint64 = 0
var m sync.Mutex

var prodJoin chan int = make(chan int)
var consJoin chan int = make(chan int)

func consumer( chans [] chan uint64 ) {
        var count uint64 = 0
        for {
                if cons_done { break }
                
                select {
                        case <- chans[0]:
                                if ! prod_done { count++ }
                        case <- chans[1]:
                                if ! prod_done { count++ }
                        case <- chans[2]:
                                if ! prod_done { count++ }
                        case <- chans[3]:
                        default:
                }
        }
        m.Lock()
        total_operations += count
        m.Unlock()
        consJoin <- 0
}

func producer( chans [] chan uint64 ) {
        var count uint64 = 0
        for {
                if prod_done { break }
                select {
                        case chans[0] <- count:
                        case chans[1] <- count:
                        case chans[2] <- count:
                        case chans[3] <- count:
                        default:
                }
                count++
        }
        prodJoin <- 0
}

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

func main() {
        switch len( os.Args ) {
                case 3:
                        if os.Args[2] != "d" {                                                  // default ?
                                ChannelSize, _ = strconv.Atoi( os.Args[2] )
                                        if ChannelSize < 0 { 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 );
        Prods = Processors /2
        Cons = Processors / 2

        // fmt.Println("Processors: ",Processors," Channels: ",Channels," ProdsPerChan: ",ProdsPerChan," ConsPerChan: ",ConsPerChan," Channel Size: ",ChannelSize)
        
        chans := make( [] chan uint64, Channels )
        for i := range chans {
                chans[i] = make(chan uint64, ChannelSize)
        }
        for j := 0; j < Prods; j++ {
                go producer( chans )
        }

        for j := 0; j < Cons; j++ {
                go consumer( chans )
        }
                

        // wait 10 seconds
        time.Sleep(time.Second * 10)
        // fmt.Println("prod done\n")
        prod_done = true
        for j := 0; j < Prods; j++ {
                <-prodJoin
        }
        // fmt.Println("cons done\n")
        cons_done = true
        for i := range chans {
                close(chans[i])
        }
        
        for j := 0; j < Cons; j++{
                <-consJoin
        }

    fmt.Println(total_operations)
}