Deprecate MPI_Graph

[hjelmn]

Problem

The scalability of MPI_Graph_create() is limited due to the global nature of its arguments. We should deprecate it.

Proposal

Deprecate the following:

int MPI_Graph_create (MPI_Comm comm_old, int nnodes, const int index[],
const int edges[], int reorder, MPI_Comm *comm_graph);

int MPI_Graphdims_get(MPI_Comm comm, int *nnodes, int *nedges);

int MPI_Graph_get(MPI_Comm comm, int maxindex, int maxedges, int index[],
int edges[]);

int MPI_Graph_neighbors_count(MPI_Comm comm, int rank, int *nneighbors);

int MPI_Graph_neighbors(MPI_Comm comm, int rank, int maxneighbors, int neighbors[]);

int MPI_Graph_map(MPI_Comm comm, int nnodes, const int index[], const int edges[], int *newrank);

MPI_GRAPH

Changes to the Text

Add MPI_Graph_create() and associated functions to the deprecated interfaces. It would also be worthwhile to add examples of how to convert from using MPI_Graph to MPI_Dist_graph.

Impact on Implementations

None. Just marking them as deprecated for now.

Impact on Users

Update code to MPI_Dist_graph_create() and associated functions instead.

References

PR: https://github.com/mpi-forum/mpi-standard/pull/37
Insert any internal (other issues) or external (websites, papers, etc.) references here.

[hjelmn]

Cross-reference to mpiwg-coll/coll-issues#2

[schulzm]

Same as in issue #16 - closed #16

[tonyskjellum]

Nathan, Should there be a pull request referenced for the 2-week upcoming deadline? We can discuss at Wednesday meeting. Tony

[dholmes-epcc-ed-ac-uk]

There is one already:
https://github.com/mpi-forum/mpi-standard/pull/37
I've added it to the issue description (under References) above and back-referenced from the PR to this issue.

[hjelmn]

I will be working on the text for MPI_Dist_graph_map today. Should be ready to discuss on Wednesday.

[RolfRabenseifner]

There is no real need to deprecate the MPI-1 virtual graph interface, because it is still an efficient interface for medium size applications. Before deprecating, there should be publications proofing that the implementations of the new dist-graph-create interface are really faster than using the old interface. Whitout any such proof, we should not burden the users with such deprecation. Do such publications exist? For MPICH, OpenMPI, ...?
I'm not sure whether I should comment on #2 or hear on #89 ?

[jeffhammond]

It should not take more than an hour to write the tests that will produce the data you want. Feel free to include them here and then folks can test with their favorite implementation.