terra::rast() doesn't return a variable with workers > 1 about furrr HOT 3 OPEN

I'm not sure how big simpleFeatureCollection is but one thing to keep in mind with your current approach is that you (probably) get 16 copies of it, one for each worker, and that could be expensive

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Are you sure mediumSizeRaster = rast("twoGBraster.tif") is actually resulting in an object? It looks like it uses a relative path so the working directory on the worker may be different. You could try supplying an absolute path instead.

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If the error message for workers > 1 is to be believed, it appears somehow the call to rast() is getting skipped—even if the statement was executed and rast() had some silent error leading it to somehow return NULL instead of failing properly that should still result in the parser adding mediumSizeRaster as a workspace variable. So it seems like something might be going pretty badly wrong though, given future's limitations for flowing diagnostics from workers back to their caller, we might be stuck. (I find myself often wishing for plan(multithread) but that's not on furrr.)

If it was a pathing issue, which it presumably isn't since there's no issue with workers = 1, I'd expect to see something like the usual

Error: [rast] file does not exist: twoGBraster.tif
In addition: Warning message:
twoGBraster.tif: No such file or directory (GDAL error 4) 

come back. But future may not be able to route that.

I'm not sure how big simpleFeatureCollection is

Good question! It's only a couple MB, so negligible in this context—32 workers would be better but even 8 GB per worker is maybe asking too much (if this approach to the task had worked I was prepared to kill the future_map() and try with eight workers to get 16 GB DDR per worker if physical memory was going to be exceeded).

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