values) I noticed something that's a little awkward. Namely, for almost everything that's indexable in hansl, the index starts at 1, but with MPI we've carried over the underlying MPI specification in which the indexation of processes starts at 0

2) If backward-compatibility turns out not to be a serious issue, do we think it's worthwhile to switch to 1-based MPI process IDs?

On Sat, 14 Jan 2017, Allin Cottrell wrote: > This relates to the thread started By Sven in > http://lists.wfu.edu/pipermail/gretl-devel/2017-January/007254.html > but I think it merits a thread of its own. > > When working up an MPI-based variant of the task Sven's talking about > (launching a bunch of parallel processes, each of which carries out the > same basic computation but with a process-specific set of parameter values) > I noticed something that's a little awkward. Namely, for almost everything > that's indexable in hansl, the index starts at 1, but with MPI we've > carried over the underlying MPI specification in which the indexation of > processes starts at 0 (so n parallel processes have IDs 0 to n-1). > > So long as what's in place is clearly documented (and I think it is), a > hansl coder should be able to handle this without huge difficulty. > Nonetheless I wonder if we'd be better to identify MPI processes in hansl > using a 1-based index. This would be easy to arrange, but would be > backward-incompatible. Which leads to two questions: > > 1) Does anyone at this point have an investment in gretl-MPI scripts that > use 0-based process IDs? (I suspect not, but maybe I'm wrong.) I really don't think so. And even if it were so, anyone who's savvy enough to write scripts using our MPI functions in a non-trivial way should have no problem adjusting to the new convention. > 2) If backward-compatibility turns out not to be a serious issue, do we > think it's worthwhile to switch to 1-based MPI process IDs? Having said the above, I don't see huge advantages either; In fact, the idea that there is a "#0 worker", perhaps makes it a little bit more evident that that worker has a somewhat different, specialised role. However if others feel otherwise, I wouldn't insist.