Re: [Gretl-devel] gretl-MPI process IDs

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.)

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?