Mantra Checkpoint Tiles

[benderonline]

I have a long-ish PBR render (4-5hr frame) that ran to 66% with checkpoints enabled before timing out on the farm. I resubmitted the frame with checkpoints enabled and got the message:

>Resuming from checkpoint file: read 4040 tiles from /path/to/bla_sh004_lighting_v010_bty.1062.exr.mantra_checkpoint

(I presumed this meant a successful resume) I then watched as my new render started from exactly the same tile as the first render... it didn't seem to actually skip any part of the render. Is this expected behaviour? Am I misunderstanding checkpoints? I figured this should start back up SOMEWHERE near the percentage of completion I got up to previously, but it appears that's not the case...

edit: interesting observation is that looking at the images in Nuke, the same tiles (up to 66%) in the EXR are there - just a hunch that the new render is just rendering straight over the old tiles instead of recognising that they've, in fact, been completed. Is this possible?

 

Edited May 19, 2016 by benderonline
Updates

[Stuart Levy]

The below looks like a clue, from the Houdini 15 release notes.   Checkpoint files are only used when resuming a render if you enable "Resume from checkpoint files" on the /out/<whatever> render node.   It looks like the parameter is named "vm_readcheckpoint".
 

Quote

By default Mantra now writes out "checkpoint" files containing the current render state at certain intervals. If the render fails because of a fixable problem such as out-of-memory, you can resume the render from the last checkpoint by turning on Resume from checkpoint files on the render node.