Coming to this a bit late, so perhaps heterogeneous OpenCL GPU/CPU netrender has already been implemented...? This is discussed/promised as Github issue:"Netrender support for gpu rendering #529"
Agree with @zebastian : whole images to be rendered by each machine, but only applies to animation jobs. For a single image, there's no option but to farm out the work as per current netrender - but using tiles, of course. The current line-based work allocation has poor efficiency. From observation, the client gets a chunk of work, sweats its CPUs for ~sec and then snoozes for ~sec while the server (presumably) updates the working image, and allocates the next line = lots of idle time on the client(s)
There are trade-offs to be made about tile-sizes and efficiency, which add further complexity to the UI/settings options. AKA: "Tuning Opportunities"(TO).
Comparing images produced by CPU (without OpenCL) and GPU (with OpenCL) there are visible differences. For animations - currently - combining such sequential frames can be messy. Hopefully heterogeneous CPU/GPU OpenCL netrender will produce homogeneous images! (Compromise on precision, perhaps?...)
BTW, it makes sense to send <batches> of frames to an OpenCl GPU PC, in order to minimise OS/network overheads. OpenCL GPU boost is so fantastic that it's a crying shame to hobble such a thoroughbred by feeding it a frame at a time.
I have a small farm of a Win10 (server) and 9 Mint (client) PCs (i.e. Linux Mint not 'mint condition'). However, only 6 have lowish-spec cards (GTX-750Ti, 960, 1060). Pending the release of OpenCl GPU netrender, I had great fun in hacking an old Python-based server/client job manager wot-I-wrote to farm out an example animation job (Robert Pancoast/menger-coastn) to the MB2 cli on the 6 GPU PCs.
- Total Frames: 35,280
- Total Elapsed : 14:38 hrs***
- Actual Elapsed: 02:31 hrs
- Average frame render times <2 seconds, depending on card type.
- Batch sizes from 10 to 20 depending on card-type.
Wahey! Lots of TO fun still to to be had.
So - Bring on OpenCl Netrender!!
***No idea how long that would take with a single PC without OpenCL - it's too horrible to think about....
Well, actually, using the 9 PCs in non-OpenCL CPU netrender mode for the same example, at 1% of frames, the completion estimate shown at one time was as low(!) as 2d 2h 40m. Times 9? Ugh!
Linkback: https://fractalforums.org/mandelbulber/14/opencl-netrender-gpucpu/2851/