It is not that uncommon that I recover using a different number of processors. Every time I do this I see the error file cluttered with messages like
WARNING level 1 in thorn CarpetIOHDF5 processor 21 host c312-313.ls4.tacc.utexas.edu (line 640 of /work/00920/tg459479/Cactus/arrangements/Carpet/CarpetIOHDF5/src/Input.cc): -> Variable AHFINDERDIRECT::ahmask on rl 0 and tl 0 not read completely. Will have to look for it in other files
I expect this, this is not an error and not really something to warn about. I acknowledge that this might have been introduced when recovering using the same number of processors was a problem and caused reading all files, but I don't think this is an issue anymore.
I propose to change the warnlevel for this message to CCTK_WARN_DEBUG(4). In addition it would be good to have one separate message with level CCTK_WARN_PICKY(3) if any variable/reflevel/timelevel could not be read completely (but not one for each of these), ideally only once for all processors. This would not clutter the output of the default simfactory runs (-L 3) too much, but would indicate that this happened - and in case this is a problem it's easy to enable -L 4.