Hello, First post to the discussion board. I made the mistake of upgrading to macOS 11.2 (aka Big Sur). I was able to build MPICH 3.4.1 successfully and integrate it with an application. However, when I ran, MPICH crashed. Here is the initial output: Abort(1) on node 0: Internal error 0 libpmpi.12.dylib 0x00000001068c2159 MPL_backtrace_show + 57 1 libpmpi.12.dylib 0x000000010684e874 MPIR_Assert_fail + 36 2 libpmpi.12.dylib 0x0000000106897bc8 MPIDI_OFI_mpi_init_hook + 4472 3 libpmpi.12.dylib 0x00000001068790d3 MPID_Init + 3091 4 libpmpi.12.dylib 0x00000001066ae70b MPIR_Init_thread + 219 5 libmpi.12.dylib 0x00000001064bb897 MPI_Init + 279 I have not yet dug into the issue any further. Before doing so I wanted to first check to see if others have successfully built and run via macOS 11.2. If so I would appreciate any pointers. If it is known that it will not yet work, that would be good information as well so not to spend anytime digging. I should note that on another machine, I was wiser and upgraded to macOS 10.5.7 (aka Catalina) and built and ran with 3.3.1 that worked fine running in parallel. Cheers, Allen Allen Sanderson SCI Institute University of Utah