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How to clip GDF? (GDF2GDF - performance)

  • November 25, 2015
  • 4 replies
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Hi FME Experts, I am looking for a solution how to clip GDF data to a given polygon and write it back to GDF. The dataset is quite big, 3 separate GDF-files with around 1.5 GB each. The polygon what needs to be clipped includes data from all separate GDF-files. In my understanding, it is necessary to build the level2 geometry when reading the GDF. The clipping and even more the FME writer takes ages to complete. The workbench is now running for more than 60 h (Workstation with FME 2015 x64, SSD, >32GB Ram). From 79.661.195 objects, only 888.756 are clipped and written back to the GDF. Any idea how to speed this up, what it the bottleneck? The GDF writing process in general? Thanks!
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4 replies

david_r
Celebrity
  • david_rCelebrity
  • November 25, 2015
First and foremost: are you using Clipper type "Clippers first"?

This can make a big difference in performance, see also the releavant section of the help text.

David

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  • twain
  • Author
  • November 25, 2015
Yes, I tried this one. The Clipper is currently just one polygon, so it makes sense. But not a big difference.
david_r
Celebrity
  • david_rCelebrity
  • November 25, 2015
Yes, I tried this one. The Clipper is currently just one polygon, so it makes sense. But not a big difference.

For curiosity, is your clipping polygon very complex/detailed? If so, one strategy could be to only clip those polygons that actually intersect the bounding box of the clipper, i.e. split the process in two stages ("if intersects then Clipper else none")

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  • twain
  • Author
  • November 25, 2015

For curiosity, is your clipping polygon very complex/detailed? If so, one strategy could be to only clip those polygons that actually intersect the bounding box of the clipper, i.e. split the process in two stages ("if intersects then Clipper else none")

Hi David,

the polygon is not very complex. I'm now running a test-run with a BBOX clipper only and "Clippers First".

My guess is somehow that the GDF read, and even more write process (building the level0-2 geometry) are somehow the bottleneck. GDF is just...

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