Michael Howard

> Perhaps the rigid body tutorials can be improved to show more clearly how users should initialize parameters like mass for their constituents. We will definitely need to do this...

Oops, sorry about that! Should be taken care of.

Not stale—haven't had time to finish this off.

@joaander I will rebase this onto `trunk-major` and finish this week.

@joaander this should be ready to take a look at! I updated the regular particle communicator to use these new data structures, but I didn't touch the use of `bcast`,...

FYI: In running with one of the other branches that didn’t have this fix, I found that some MPI libraries internally check and report the error we were unintentionally triggering...

It is indeed strange and frustrating. It should be addressed as part of the MPI-4 standard, but that will probably take a while to percolate through the implementations. https://www.mpi-forum.org/docs/mpi-4.1/mpi41-report/node499.htm#Node499