Hi Jack, Thanks for this. This lines up with some reports we have had from new installations on MacOS. I have just managed to reproduce this by upgrading to OpenMPI 3.0.0 . It looks like some issue between mpi4py and OpenMPI. I’ll report a bug upstream and see what they say. In the meantime, I note that this isn’t actually a bug in Firedrake’s parallel functionality, it’s just something which prevents the test framework from successfully running parallel tests. So it’s a bit irritating and we need to fix it but it shouldn’t prevent you doing what you need to do with Firedrake. Regards, David On 13 Mar 2018, at 12:17, Jack Betteridge <J.D.Betteridge@bath.ac.uk<mailto:J.D.Betteridge@bath.ac.uk>> wrote: Hi, I am trying to fix my firedrake install. I appear to be failing all of the parallel tests (200 or so). I have narrowed the problem down to the way pytest is calling MPI and have a minimal failing example: from subprocess import check_call from mpi4py import MPI check_call(call) comment out mpi4py line and it runs fine In anticipation of XY problem, I'm just trying to pass the firedrake tests. (this is openMPI 3.0.0 on my Arch Linux install, but verified failing on another system also) I'm not yet on the mailing list, but this is cross posted in slack. Cheers, Jack _______________________________________________ firedrake mailing list firedrake@imperial.ac.uk<mailto:firedrake@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/firedrake