[Gretl-devel] Re: bug with "const" in function

On Fri, 2 Feb 2024, Sven Schreiber wrote: Right, but that happens automatically within any given gretl process, regardless of whether any series, or list of series, is passed to the called function. As a trivial illustration: <hansl> function void f (void) print const smpl end function nulldata 8 setobs 4 2016:1 f() </hansl> In the MPI context the dataset (if present) is not automatically passed between distinct gretl processes, but this is ensured by the --send-data option for a mpi block. Another trivial illustration: <hansl> function void f (void) printf "process %d\n", $mpirank print const smpl end function nulldata 8 setobs 4 2016:1 mpi --send-functions --send-data f() end mpi --np=2 </hansl> There's one gotcha to note here. If you don't need to pass the entire dataset in the MPI context you can use --send-data=L, where L is a list of series, BUT this won't work if L contains just const. That's because inter-process transfer of data is done using a gdt or gdtb file, and "const" is not explicitly represented in such a file. Trying to save a gdt[b] file containing no series other than const will fail with the message "No data to save!". It's fine if L contains just a single series, but it can't be series 0. You could insert "list L = index" before the mpi block above, and make the option --send-data=L. Anyway, the behavior you found with exists() is clearly wrong, and I'm satisfied that a proper fix can be engineered: we'll give the called function a copy of const under the parameter name rather then doing the "shift and rename" thing. That should be in git quite soon. Allin