Not so long ago there was an issue where exporting images that contain diffuse and sharpen module would take a crazy long time on an ancient system (yes, Windows 10, 4Gb RAM, on board graphics, I know!!)
It was pointed out that there was some kind of ‘tiling’ setting (forgive my fragile memory) that by default had a very strange value.
Changing that (again I can’t remember to what !??!) meant that export times for me came down to about 3 mins, perfectly acceptable for me.
In DT4.0 my export times have now increased to about 15mins.
I went looking for this setting but can’t seem to find it.
Has it been moved? removed? Or is there another way to tweak this?
Thanks
It might be worth looking through the performance section in the user manual
Thanks Chris, already did that but there is nothing really to do with ‘export’.
In fact it states something like speed of export is down to the speed of the internal algorithms for the modules.
However there was definitely some sort of setting that was accessible via ‘preferences’ that seems to have gone walk about in DT4
I think it might be the “minimum tiling buffer size” referenced on that page. There aren’t really separate perf settings for “export”.
Martin,
I had a similar issue a few weeks ago and eventually tracked it down.
In the export module I had accidentally set high quality resampling to yes and this made a massive impact on my export times when using diffuse or sharpen .
When I reset this back to no the export were so much quicker.
This may not be your issue however I thought I would mention it.
Phil.
Thanks Chris something like that does ring a bell.
Been comparing the darktablerc from my 3.8 install and the new 4.0 and ‘resource_default’ settings etc must be new as they don’t exist in the 3.8 rc file.
Can’t find anything in the 3.8 rc file that rings a bell either…maybe its the heat.
Also in the manual it states that this is historical and should be left at default so not sure what to set it to?
Thanks Phil but mine is set to ‘no’ already
Yeah I’m not sure either. Perhaps @hannoschwalm can help.
Be careful with that setting.
With it enabled, you should get exports that match what you see in the darkroom at 1:1 (100%) view: the image is processed at full resolution, and then downscaled. Otherwise, processing occurs at lower resolution. Parameters and algorithms that involve pixel sizes may not produce the same results. 10 pixels on a 1920x1280 image is not the same as on 6000x4000. Even if the parameters are adjusted, that won’t be exact in many cases: for example, an algorithm will probably use 3 pixels instead of the fractional 3.2 that would reflect the 6000 → 1920 scaling. The artefacts introduced by the scaling will also affect the output (if you sharpen first, then scale, you’ll get different results than if scaling first, then sharpening).
On such a low mem system the export time will Mainly be determined by 1) possible upscaling 2) high quality and 3) tiling.
Point 3 will likely be your problem, you should first use resources set to large. Or you might tune your setting for the used resource level as described in the manual. But large will likely be a good setting…
Thanks
Already ‘large’.
Therefore ‘minimum tiling buffer size’ is 0.0625 on my system.
Being unsure how this works is it better to increase the min buffer size or decrease it?
I vaguely remember when this cropped up before AP said bigger tile size was quicker but not really sure. (sorry for my fogginess, I really should write things down!!!)
Update:
Okey, dokey, hopefully this may help other people.
Changed this in the darktablerc from:
resource_large=700 16 128 900
to:
resource_large=700 32 128 900
Effectively setting the min tiling buffer to 0.125 on my system.
Export times have now halved from 15 mins to 7 mins !
Thanks for all the helpful pointers, I’ll keep tweaking
That is a fair point. The default is disabled.
If I enable it and use say diffuse or sharpen then it takes many minutes to export a single image and my system freezes.
I only have a 2GB graphics card and may upgrade at some point.
Yeah, you got it. 
just beware that this might lead to lots of mem used in tiling that could lead to system instability.
I treat export now like a lit firework, stand well back.
System instability, ha! it can do what it likes I’m usually off making tea. 
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