MPI (`sisl.mpi`)

Optional MPI support. All functionality works without mpi4py, in which case the communicator is a serial stand-in.

See Distributing work with MPI for a guide on how to use it.

Communicators

`get_comm`()	The communicator sisl is using, acquiring it on first call.
`BaseCommunicator`	The communicator contract sisl relies on.
`Communicator`	An mpi4py communicator plus the provenance needed to behave correctly.

Distributions decide which rank owns which indices. Calling one on an object forwards to the object’s __sisl_distribute__ method.

`Distribution`	Maps `n` indices onto the ranks of `comm`.
`BlockCyclicDistribution`	Blocks of blocksize indices dealt round-robin, as ScaLAPACK lays out a matrix.

Helpers for objects that implement __sisl_distribute__ and need to track whether they have changed since they were last distributed.

`DistributionState`	Distribution state carried by a distributed object.
`distribute_changes`(method)	Mark method as invalidating the distribution of its object.