Using MPICH 3.1.4, I'm getting internal assertions of this kind

of when using MPI_Dist_graph_create :

Assertion failed in file src/mpi/topo/dist_gr_create.c at line 223: s_rank >= 0

Assertion failed in file src/mpi/topo/dist_gr_create.c at line 195: sources[i] < comm_size

I've checked that ranks passed in are in the proper range,

rather I think the issue is caused by requesting an edge

from rank 0 to itself.

(Another hint is that its non-deterministic which assertion

I get; it depends on the order in which the ranks get scheduled

by the OS, so there is a bit of a bug in the implementation,

or at least no check for self-edges).

Does the MPI standard allow for self-edges in these graphs ?

Thank you,

P.S. - I'll throw in a bigger question while I'm at it: are

MPI_Dist_graph_create and MPI_Neighbor_alltoallv

implemented with optimally scalable algorithms ?

I'm betting my scalability on them being roughly

O(log(P)) where P is communicator size, assuming

neighborhood sizes and message sizes are constant.