Re: [Gegl-developer] [Gimp-developer] GEGL_THREADS

[Nathan Summers <rockwalrus gmail com>]

Awesome!

Rockwalrus

On Tue, Jul 1, 2014 at 2:40 PM, Øyvind Kolås <pippin gimp org> wrote:
> GEGL master can now be thread-accelerated. Different approaches have
> been tried; the approach that first yielded promising results was
> parallelizing each individual operations process call. Most GEGL
> operations now have threading support; some are opted out of the
> automatic threading provided by the base classes by setting
> operation_class->threaded = FALSE in their respective class_init
> functions.
>
> The original plan was making each thread do a full graph processing,
> but initial profiling of that approach gave worse results than doing
> it individually per op. Doing it individually per op has the added
> benefit that each op can be free to use different parallelization
> techniques, OpenMP, OpenCL or thread-pool provided by GEGLs base op
> classes.
>
> It is not enabled by default yet; since it still might be crashing or
> giving wrong results. To test it, run GEGL/start GIMP with
> GEGL_THREADS set to the number of threads to use and GEGL_USE_OPENCL
> to "no" in the environment (with this threaded processing; we probably
> do not want to use on CPU based OpenCL implementations). The full
> environment I currently test my GIMP with is:
>
> GEGL_USE_OPENCL=no GIMP_DISPLAY_RENDER_BUF_SIZE=256x512
> GIMP_PROJECTION_CHUNK_SIZE=256x512 GEGL_TILE_SIZE=256x128
> GEGL_THREADS=2
>
> Some of the ops with ->threading=FALSE in class_init are implemented
> in non-thread-safe ways or rely on the wrong arguments for determining
> their geometry.
>
> There is room for improvement in re-arranging/adding more local locks
> in GeglBuffer. A bigger improvement might be adding new API for
> threaded buffer iteration; combined with refactoring of how threading
> is done at for point-filter/-composer /-render/transform sub-classes
>
> /pippin
>
> (please continue this thread on gegl-developer-list and not gimp-developer)
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