On Tue, Sep 4, 2018 at 4:57 PM Andreas Neumann <a.neum...@carto.net> wrote:
> Hi Alessandro, > > Thanks for the clarification that only the change of the OpenCL-device > needs a restart. > > I tried both - acceleration in CPU and in GPU. I had the impression that > the acceleration in the CPU was slightly faster than in the CPU - but not a > lot faster. Maybe the GPU (Intel HD Graphics 4600) is not too powerful. It > is a ThinkPad notebook, not a desktop. > Thanks for the info! Yes, maybe that the lower I/O (there is no need to transfer data to/from the graphic card) compensates the slower processing on the CPU Cheers Greetings, > > Andreas > > On 2018-09-04 15:56, Alessandro Pasotti wrote: > > > On Tue, Sep 4, 2018 at 2:21 PM Andreas Neumann <a.neum...@carto.net> > wrote: > >> Hi Alessandro, >> >> I just tested if the hardware acceleration (OpenCL) helps in the live >> hillshade renderer. >> > > > Hi Andreas, > > thanks a lot for your feedback, I honestly am a little worried about the > possible problems on different platforms, graphic cards and driver > versions, I choose to stay on the safe side and there is a safeguard that > disables the OpenCL support at the first issue in the renderer. > > The processing algs looks generally more stable (never got a single crash > myself). > > > >> The good news is that it works stable so far and substantially improves >> rendering time of the live hillshade renderer. My notebook on my workplace >> is rather slow. Without hardware acceleration it renders the hillshade in >> approx 8 seconds (large window on two screens). With OpenCL acceleration >> set to on, it renders in about 1 second or even less. I assume quite some >> time is also spent on reading the file. This with resampling on (average >> for zooming out and bilinear for zooming in beyond native resolution). >> > > Yes some time is spent on reading the file and some time is spend on I/O > tranferring data to/from the graphic card, this means that the performance > gain is usually higher on larger images than on smaller images. > > >> Hardware is an Intel HD Graphics 4600. The CPU is also listed as >> supported. >> > > Can you also try the CPU? I'm curious about the performances. > > >> Visually, with or without HW accelation on, there still are some >> rectangular artefacts in both versions. >> > > Yes: that does not change, the algorithm is pretty much the same in both > implementations. > > > >> Tested on Windows. >> >> -------------- >> >> One more thing: on my machine there is no restart of QGIS necessary for >> the changes (HW acceleration on of off) to be applied. This is contrary to >> the statement in the settings dialogue, which says, that a restart of QGIS >> is necessary. >> > > The text can probably be improved: what needs a restart is if you change > the device, enabling and disabling OpenCL support does not require a > restart. > > >> --------------- >> >> Thanks a lot for your work! >> > > > Thank you for the feedback! > > > > > -- > Alessandro Pasotti > w3: www.itopen.it > > > -- Alessandro Pasotti w3: www.itopen.it
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