code review 3280044: sort: avoid overflow in pivot calculation.

sort: avoid overflow in pivot calculation.
thanks to snilsson@nada.kth.se for the original CL.

[r, 2010-11-30 18:18:56]

Hello gri (cc: golang-dev@googlegroups.com, snilsson@nada.kth.se),

I'd like you to review this change.

[gri, 2010-11-30 18:22:18]

LGTM
- gri

On Tue, Nov 30, 2010 at 10:18 AM, <r@golang.org> wrote:

> Reviewers: gri,
>
> Message:
> Hello gri (cc: golang-dev@googlegroups.com, snilsson@nada.kth.se),
>
> I'd like you to review this change.
>
>
> Description:
> sort: avoid overflow in pivot calculation.
> thanks to snilsson@nada.kth.se for the original CL.
>
> Please review this at http://codereview.appspot.com/3280044/
>
> Affected files:
>  M src/pkg/sort/sort.go
>
>
> Index: src/pkg/sort/sort.go
> ===================================================================
> --- a/src/pkg/sort/sort.go
> +++ b/src/pkg/sort/sort.go
> @@ -63,7 +63,7 @@
>  }
>
>  func doPivot(data Interface, lo, hi int) (midlo, midhi int) {
> -       m := (lo + hi) / 2
> +       m := lo + (hi-lo)/2 // Written like this to avoid integer overflow.
>        if hi-lo > 40 {
>                // Tukey's ``Ninther,'' median of three medians of three.
>                s := (hi - lo) / 8
>
>
>

[r, 2010-11-30 18:38:02]

*** Submitted as http://code.google.com/p/go/source/detail?r=5101194d056f ***

sort: avoid overflow in pivot calculation.
thanks to snilsson@nada.kth.se for the original CL.

R=gri
CC=golang-dev, snilsson
http://codereview.appspot.com/3280044