Thanks everyone for the interesting comments!
The discussion on what the future could be is very interesting. For example, I also would like to know what are the optimizations one could do at compile stage for specific cpus/gpus; I have compiled DT myself even if I’m not a programmer so maybe a short note/guidelines to be included in the online manual or even here could be interesting for me (and I guess for many others; certainly not for the majority of the users that will be however happy with the official releases).
About the state of things in DT development (what @anon41087856 defines as an “anarchic”) I guess unless somebody steps up and all other developers agree on this, we may have to be happy with the current situation. It certainly is an incredible success regardless to have Darktable in the current state, that gives people like me (Linux and open source supporters) a viable alternative to commercial apps.
About the present situation: I have rewatched a few online tutorials, e.g. the nice visual-only videos by @s7habo and I have noticed that the way DT reacts interactively to user input it perhaps similar to my experience (as opposed to the fluidity that Lightroom has, as I mentioned at the beginning). I may have to do some short screencasts showing what is my personal experience just to understand if this is the reality that all other users live with.
I have also re-discovered some benchmarking that maybe we could do all together as a community and gather the results; it is mentioned here with some exotic machinery that I will not even start to compare my laptop to, and here. These are the files (raw and processing history):
http://www.mirada.ch/bench.SRW
http://www.mirada.ch/bench.SRW.xmp
These are the command to run DT from command line with and without openCL:
$ darktable-cli bench.SRW test.jpg --core -d perf -d opencl
$ darktable-cli bench.SRW test.jpg --core --disable-opencl -d perf -d opencl
You will get some stats and take the last line as indicative of the time spent to do the entire processing, e.g.:
15,684476 [dev_process_export] pixel pipeline processing took 12,885 secs
I’ve run them a few times then averaged the results and what I get on my laptop (Dell XPS-15 with i7-7700HQ@2.8Ghz, Geforce GTX1050, 16 Gb ram, 512 Gb ssd) is:
~13 secs with opencl
~80 secs cpu only
I have also played with opencl parameters following some advice found here but can’t say I have noticed a lot of differences. I’m not sure if this benchmark tests the fluidity of the user epxerience, which is what I’m after, but at least if I can compare my results to those of similar machines I will at least get to know if my laptop is behaving “as expected” or not.