Add note about progress on the topic this project was initially designed to look at

README.md

@@ -64,3 +64,14 @@ eager exchanges are working and what effect the size of the packets has.
 
 ---------------------------
 Peter W. Draper 24 Sep 2019.
+
+Continuing from the notes above, there are also RDMA based versions of
+swiftmpistepsim, which are found in the various branches of the
+repository. That work and a re-working of SWIFT to use RDMA revealed that the
+main driver for the delays wasn't the scatter in MPI completion, but the time
+taken to copy data into and out of registered memory, the best solution to
+which was to make better use of the memory bandwidth by copying using multiple
+threads.
+
+-----------------------------
+Peter W. Draper 24 April 2023.