Greetings - As you may know, Open MPI 5.0 is going to include an ambitious improvement in Open MPI's runtime system along with a number of performance improvements, and was targeted to ship this summer. While we are still going to make those improvements to our runtime system, it is taking us longer than we anticipated and we want to make sure we get everything right before releasing Open MPI 5.0 later this year.
To get many of the performance improvements to the MPI layer in your hands sooner, the Open MPI development team recently made the decision to start a 4.1 release series. Open MPI 4.1.0 will be based off of Open MPI 4.0.4, but with a number of significant performance improvements backported. This includes improved collective routine performance, the OFI BTL to support one-sided operations over the Libfabric software stack, MPI I/O improvements, and general performance improvements. Nightly tarballs of the 4.1 branch are available at https://www.open-mpi.org/nightly/v4.1.x/ and we plan on releasing Open MPI 4.1.0 in July of 2020. Thank you, The Open MPI Development Team
