Reduce repeat count for picture_playback benchmarks

[TomH, 2012-06-26 13:51:44]

picture_playback benchmarks dominate the bench timings.

Is there a reason they have N=1000, or can we dial them back to N=250 to get
their cost more in line with the other benchmarks? N=250 takes the iteration
time from c. 750ms to c. 150ms.

Running bench -repeat 100 -config GPU -match picture_ 4x on linux shows only
about 2% noise at N=250, which is relatively good.

[epoger, 2012-06-26 13:52:58]

LGTM

Looks like you set it to 200, not 250; either one is fine with me.

[TomH, 2012-06-26 13:53:25]

On 2012/06/26 13:52:58, epoger wrote:
> LGTM
> 
> Looks like you set it to 200, not 250; either one is fine with me.

That would explain why I was seeing 5x speedup instead of 4x, wouldn't it?

[DerekS, 2012-06-26 14:24:02]

On 2012/06/26 13:53:25, TomH wrote:
> On 2012/06/26 13:52:58, epoger wrote:
> > LGTM
> > 
> > Looks like you set it to 200, not 250; either one is fine with me.
> 
> That would explain why I was seeing 5x speedup instead of 4x, wouldn't it?

lgtm

[TomH, 2012-06-26 14:26:09]

Committed with r4339.