pi.read() of tif file gives all zeros in distributed mode

[grodgers1]

Hi!

First of all, thanks for the great tool!

I have been developing some python scripts using pi.distribute(Distributor.NONE), but I've running into issues when trying to switch to either LOCAL or SLURM distributed modes. After some debugging, I figured out the issue seems to be that pi.read() can't read 3D .tif volumes in distributed mode. pi.writetif() throws a RuntimeError that it can not be used in distributed computing (and the documentation warns that this isn't possible). It would be useful if pi.read() raised some errors as well to avoid confusion. At the moment it seems to just return an image of all zeros. Also, it woud be useful if the documentation (https://pi2-docs.readthedocs.io/en/latest/reference/read.html) warned against this issue, as it currently reads as if pi.read() can be use without problems in distributed mode.

Best wishes,
Griffin

[arttumiettinen]

Thanks for pointing out this important issue. Looking at the code, indeed, this is a serious problem, and there should be an error message noting the incompatibility between tif reading and distributed processing. Even better, reading tif files in distributed mode could be possible with some caveats. I will put this on my todo list, but the fix won't be available before August due to summer holidays.