cycles slowdown since > r52555


after r52555 I had a slowdown in cycles rendering of about 15 % in all scenes, no matter what distribution I use, from builderblender or graphicall and no matter if it’s win64 or MinGW.
Everytime I use the several unchanged testfiles. (Don’t ask for this file, they are really heavy)
The question is if there is anybody else who noticed this slowdown.

Oh, and in the latest Win64 build there is a massive increase of fireflies in one of this scenes (8 glasses, one after another).

Again, this is a question if I’m alone with this mutation, or if I should make a bugreport.


Win7 64, i3930, gtx580

Here is a quick rendering which shows the rendertime and fireflies in r52555 versus r52698.
Also notice the darkness of the glasspack in r52698.


P.S.: Please ignore the statement above concerning MinGW, it’s a fault, because there isn’t any newer MinGW build.

I think the shading issue was due to a sample weighting error that Brecht fixed in Rev 52704.

As for the slowdown, that might be due to some rather substantial changes to the sample weighting that began with a couple of large bugfixes for materials with large numbers of shader nodes and materials using a combination of mix and add shader nodes. This culminated with another set of tweaks to fix some artifact issues with tiled rendering.

I recommend you get a new build after the mentioned revision and see if you get better results, otherwise it might be enough of a concern to file a bug report.

Yes, you are right, with r52708 the graphical issue is fixed.
But, the rendertime increases again up to 8:15 min.


Check your render tiles. Recently tile size was changes from “number of x and y tiles” to “size of tiles in pixels”. They are more than likely not set to the ideal settings for your scene, and in certain situations setting the correct tile size can cut render times almost in half.

Yes, I know, but the increase of rendertime happens during the newer builds >52555, after my settings are already adjusted to 512x512 in the scene above.

Thanks anyway,

Oh, may I infer from your answer(s), that you or any(every)body else can’t confirm the increase of rendertime ?


Waiting for a new mingw build - I’ll let you know once there is one.

I know 51011 is faster than later builds. Approximately 15%.