package main

import "fmt"
import "log"
import "os"
import "time"
import "strconv"

func assert_eq(a, b int64) {
    if a != b {
        log.Fatalf("assertion failed\nleft: %d, right: %d\n", a, b)
    }
}

func do_rec(ch chan int32, resch chan int64, n int32) {
    var sum int64
    var i int32
    for i = 0; i < n; i++ {
        sum += int64(<- ch)
    }
    fmt.Println(sum)
    resch <- sum
}

func do_send(ch chan int32, start, end int32) {
    for i := start; i < end; i++ {
        ch <- i
    }
}

func main() {
    if len(os.Args) != 5 {
        log.Fatalf("usage:\n\t%s <nsend> <nrec> <buflen> <nobj>\n", os.Args[0])
    }
    nsend, _ := strconv.Atoi(os.Args[1])
    nrec, _ := strconv.Atoi(os.Args[2])
    buflen, _ := strconv.Atoi(os.Args[3])
    nobj, _ := strconv.Atoi(os.Args[4])
    stopwatch := time.Now()
    ch := make(chan int32, buflen)
    resch := make(chan int64, 0)
    no := nobj
    for i := 0; i < nrec; i++ {
        n := no / (nrec - i)
        go do_rec(ch, resch, int32(n))
        no -= n
    }
    assert_eq(int64(no), 0)    
    no = nobj
    for i := 0; i < nsend; i++ {
        n := no / (nsend - i)
        end := no
        no -= n
        go do_send(ch, int32(no), int32(end))
    }
    assert_eq(int64(no), 0)    
    var sum int64
    for i := 0; i < nrec; i++ {
        sum += <-resch
    }
    elapsed := time.Now().Sub(stopwatch)
    rate := float64(nobj)/float64(elapsed.Nanoseconds())*1000.0
    duration := 1.0e-09 * float64(elapsed.Nanoseconds())
    fmt.Printf("%d objects in %g s (%.2f objs/µs)\n", nobj, duration, rate)
    expected_sum := int64(nobj)*int64(nobj-1)/2
    fmt.Printf("got: %d, expected: %d\n", sum, expected_sum)
    assert_eq(sum, expected_sum)
}