where is c2g in Gimp 2.10.12 ?

[pistikem]

hello, i am new to this forum.  i just began to use the new Gimp v2.10.12 and i miss the c2g function i made use of for many years in v2.8.  where do i find Gegl's c2g ?

[tmanni]

Menu Colors > Desaturate > Color to Gray

[pistikem]

wow, that's the thing i was looking for since yesterday - very helpful, many thanks !

2nd question : how can i change the number of CPU cores recruited for a GEGL process ?  currently it uses only 2, that's a fraction out of 16...

[tmanni]

(07-07-2019, 01:53 PM)pistikem Wrote: wow, that's the thing i was looking for since yesterday - very helpful, many thanks !

2nd question : how can i change the number of CPU cores recruited for a GEGL process ?  currently it uses only 2, that's a fraction out of 16...

Go to Menu Edit > Preferences ; in the System Resources part, you can set the "Number of threads to use".

[rich2005]

As far as I know you also need openCL enabled and a working opencl driver in your linux.

[tmanni]

(07-07-2019, 02:24 PM)rich2005 Wrote: As far as I know you also need openCL enabled and a working opencl driver in your linux.

No ; multi-threads processing and opencl processing are independant of each other.
You can use several threads without any opencl support.

[pistikem]

great, thank you both, it suddenly started to use somehow all cores available - although i didn't change the settings in preferences, but opening its menu just did it apparently.  nice speed up, as compared to v2.8 !

[pistikem]

actually, it's pretty strange - i got it once only running on all cores, and since then it wants to make use of just two cores.  any manipulation under preferences and settings doesn't make a difference...   does image type or image size matter in this respect ?

[rich2005]

You could go back to preferences and check that the number of threads are still 16. I thought that Gimp polled the system and set up accordingly...but...

I keep a cpu / memory widget in the kicker (using kbuntu here) and see the load jumping about but yes, 2 cores do seem to be favoured but not always the same ones.

I put a widget on the desktop, captured a C2G opp as a video (but can not honestly inflict that on anyone, so screenshots). Obviously processes (ffmpeg) are running in the background, but a good indication of what is going on.

Starts evenly balanced : https://i.imgur.com/IAhM38f.jpg
but by half way favours cpu0 & cpu1 https://i.imgur.com/aPTi0qV.jpg
almost finished, still mostly cpu0 & 1 but a bit of load on 3 & 4 https://i.imgur.com/o3hETk5.jpg
Takes about a minute here for that size image - 16 bit, 3400 x 3400

What does it prove? Not a lot except not to worry about it too much

[pistikem]

thank you, rich2005.  there may be something broken in my Gimp version or in the environment it runs in on my Slackware box : it usually uses 2 cores - but then when i play a bit in the Color to Gray GUI window, for example with 'split window' or even just pressing 'cancel', Gimp suddenly makes use of all cores for quite a while till the end (24 Mpxls), or interrupts this and goes back to the 2-core speed.  i monitor this with xosview or with nmon.  it's quite erratic and is annoying as i have a workflow in which i want to keep processing times as short as possible...