Dear everyone, I have a question on tagged messages and the best way to generate tags. A while back we went through the whole library and consistently tagged all of our MPI point-to-point messages - there was a long discussion about how to do this in
https://github.com/dealii/dealii/issues/8958 and some cited follow-up pull requests. This strategy is nice because it scales and we can reuse the same communicator for everything. A drawback is that there are some hard limits on the number of times we can call a particular _start() function before calling its corresponding _finish() function (e.g., with the same communicator, we can only do 10 ghost updates inside LA::d::Vector concurrently). I'm working on a problem where I want to do this communication inside some library code that will potentially be called many, many times (about 20 at once for one situation my code's predecessor deals with). Hence I want to work around these hard-coded limits in some way that does not require the caller to set tags, batch things, etc. One fix that I have found (PETSc does this) is to assign every object its own duplicated communicator which can then keep track of its own tags with MPI's own get and set attributes functions. Hence, the question: has anyone else here encountered a similar problem where they want to post potentially dozens of ghost updates or other communications at once? If so - are there better solutions than duplicating communicators? Do you happen to know if there are any downsides to making lots of MPI communicators? I'd appreciate hearing back from anyone with experience with this sort of MPI problem. Best, David Wells -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/BN7PR03MB4356CE8442C84CDB32460A5CED859%40BN7PR03MB4356.namprd03.prod.outlook.com.
