[Bf-cycles] Render tiles in GPU vs CPU

[Sergey Sharybin]

This is a bit more complicated issue. Performance on GPU is not only
depends on number of tiles, but also on particular size of tile. Making
tiles size aligned to 16 pixels made much sense when i was doing tests
during Mango. SO i could think using tile size of 1024x1024 could end up in
faster render than using single tile for HD frame.

Also, as Daniel already mentioned, you could easier run out of memory with
single tile and to make it more control over performance in such cases
pixel-based tile size makes more sense.

If you want to force single tile being used always, why don't set tile size
to 10K by 10K pixels -- it'll be clamped to actual image internally in
render engine :)


On Thu, Nov 8, 2012 at 6:37 AM, Daniel Salazar - 3Developer.com <
zanqdo at gmail.com> wrote:

> Speed is only half of the issue here. An HD (or higher) render will take a
> lot of memory and can very well crash your GPU rendering if not using
> tiles. What works for a couple models is not what works for a complete
> scene!
>
> Daniel Salazar
> patazstudio.com
>
>
>
> On Wed, Nov 7, 2012 at 6:15 PM, Cal McGaugh <cal at cal3d.com> wrote:
>
>> **
>>  Hi Adriano,
>>  very interesting..........no wonder I'm seeing longer renders with 2.64
>> vs 2.63.
>>
>>  Will do more tests with different versions. Just got a new (used) Zotac
>> GTX580
>> and will test different tile settings.
>>
>>  Thanks,
>>  Cal
>>
>>
>>
>>
>> On November 7, 2012 at 7:02 PM Adriano Oliveira <adriano.ufrb at gmail.com>
>> wrote:
>>
>>  Hi,
>>
>> Subdividing render image in tiles has very inconsistent behavior in CPU
>> and GPU: more tiles are good for CPU, BUT less are better for GPU.
>>
>> With my i7, 8x8 is ok. With my GTX 560 Ti, 1x1 is the best. With another
>> dual GTX 590 system, I've found 3x3 to be fastest...
>>
>> Problem: with 8x8 as default, non-advised GPU users are experiencing
>> longer render times.
>>
>> In last builds, tiles became pixel based, what is not good for GPU users,
>> as long as we should now set it up for equal image size and this can change
>> a lot for preview. And as strange as it gets, I’ve found that tile size of
>> 1920x1080 is fast even for a 960x540 render…
>>
>>
>>
>> I think this is getting messy.
>>
>>
>>  Adriano A. Oliveira
>>
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-- 
With best regards, Sergey Sharybin
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