func mhelp(v *vec.Vector, b, e int, c chan int) {
if debug {
fmt.Printf("mhelp(%d, %d)\n", b, e)
}
if (e - b) < 1 {
c <- 1
return
}
c1 := make(chan int)
c2 := make(chan int)
mid := (e-b)/2 + b
go mhelp(v, b, mid, c1)
go mhelp(v, mid+1, e, c2)
<-c1
<-c2
i := b
j := mid + 1
l := e - b + 1
sorted := vec.MakeVector(l, 0)
p := 0
for i <= mid && j <= e {
var m int
if *v.At(i) < *v.At(j) {
m = *v.At(i)
i++
} else {
m = *v.At(j)
j++
}
*sorted.At(p) = m
p++
}
for i <= mid {
*sorted.At(p) = *v.At(i)
i++
p++
}
for j <= e {
*sorted.At(p) = *v.At(j)
j++
p++
}
for ix := 0; ix < l; ix++ {
*v.At(b + ix) = *sorted.At(ix)
}
c <- 1
}
func MSort(v *vec.Vector) {
c := make(chan int)
go mhelp(v, 0, v.Size()-1, c)
<-c
}
func qhelp(v *vec.Vector, b, e int, c chan int) {
if debug {
fmt.Printf("qhelp(%d, %d)", b, e)
}
if (e - b) < 1 {
c <- 1
return
}
// fmt.Printf("qhelp: %d %d\n", b, e)
// lazy, so just pivot on first element
pivot := *v.At(b)
i := b + 1
j := e
for i < j {
if *v.At(i) <= pivot {
i++
} else if *v.At(j) > pivot {
j--
} else {
swap(v.At(i), v.At(j))
}
}
// everything < (i == j) is <= pivot, everything > is >pivot
if *v.At(i) > pivot {
i--
} else {
j++
}
//now [b,i] is <= pivot, and
swap(v.At(b), v.At(i))
if debug {
for p := b; p <= i; p++ {
if *v.At(p) > pivot {
fmt.Printf("%d(%d) > %d\n", p, *v.At(p), pivot)
}
}
if i+1 != j {
fmt.Printf("%d +1 != %d\n", i, j)
}
if *v.At(i) != pivot {
fmt.Printf("%d(%d) != %d\n", i, *v.At(i), pivot)
}
for p := j; p <= e; p++ {
if *v.At(p) <= pivot {
fmt.Printf("%d(%d) <= %d\n", p, *v.At(p), pivot)
}
}
fmt.Printf("%d %d\n", i, j)
fmt.Printf("[\n")
for p := b; p <= e; p++ {
if i == p || j == p {
fmt.Printf("--- %d\n", pivot)
}
fmt.Printf("%d\n", *v.At(p))
}
fmt.Printf("]\n")
}
c1 := make(chan int)
c2 := make(chan int)
go qhelp(v, b, i-1, c1)
go qhelp(v, j, e, c2)
<-c1
<-c2
c <- 1
}
