code review 6348061: math/rand: avoid use of math.Pow in tests.

math/rand: avoid use of math.Pow in tests.

The use of math.Pow for mere squaring can be extremely
slow on soft-float ARM. Even on systems with hardware
floating-point, a speedup in test duration is observed.

On amd64
Before: ok      math/rand       2.009s
After:  ok      math/rand       0.340s

Fixes issue 3740.

[dave_cheney.net, 2012-07-02 10:47:07]

Wow. I can't believe it made that much difference.

Also, fixes issue 6304087.

dfc@qnap:~/go/src/pkg/math$ time go test math/rand -test.short
ok      math/rand       58.845s

real    1m0.988s
user    1m0.640s
sys     0m0.160s
dfc@qnap:~/go/src/pkg/math$ /usr/local/bin/hg clpatch 6348061
6348061:
        math/rand: avoid use of math.Pow in tests.

        Author: remyoudompheng@gmail.com
        Reviewer: 
        CC: 
        Files:
                src/pkg/math/rand/rand_test.go

dfc@qnap:~/go/src/pkg/math$ time go test math/rand -test.short
ok      math/rand       4.708s

real    0m6.842s
user    0m6.610s
sys     0m0.240s

[remyoudompheng, 2012-07-03 22:20:54]

Hello dave@cheney.net, golang-dev@googlegroups.com (cc:
golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[r, 2012-07-03 22:25:27]

LGTM
oh my

[dave_cheney.net, 2012-07-03 22:27:35]

@r, do you think this change, http://codereview.appspot.com/6351058/,
developed at the same, is worth proposing as well (if I address the
benchmarking comments by Minux) ?

On Wed, Jul 4, 2012 at 8:25 AM,  <r@golang.org> wrote:
> LGTM
> oh my
>
> http://codereview.appspot.com/6348061/

[r2, 2012-07-03 22:35:12]

On Jul 3, 2012, at 3:27 PM, Dave Cheney wrote:

> @r, do you think this change, http://codereview.appspot.com/6351058/,
> developed at the same, is worth proposing as well (if I address the
> benchmarking comments by Minux) ?

seems easy and reasonable.

-rob

[remyoudompheng, 2012-07-03 22:38:14]

*** Submitted as http://code.google.com/p/go/source/detail?r=0f3410fdeb91 ***

math/rand: avoid use of math.Pow in tests.

The use of math.Pow for mere squaring can be extremely
slow on soft-float ARM. Even on systems with hardware
floating-point, a speedup in test duration is observed.

On amd64
Before: ok      math/rand       2.009s
After:  ok      math/rand       0.340s

Fixes issue 3740.

R=dave, golang-dev, r, r
CC=golang-dev
http://codereview.appspot.com/6348061