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Missing info. Adam Moody and Torsten Hoefler Chicago 3/28/11. Where is MPI_Info used?. Functions that take MPI_Info DIST_GRAPH_CREATE_ADJACENT, DIST_GRAPH_CREATE ALLOC_MEM COMM_SPAWN, COMM_SPAWN_MULTIPLE OPEN_PORT, COMM_ACCEPT, COMM_CONNECT, PUBLISH_NAME, UNPUBLISH_NAME, LOOKUP_NAME

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missing info

Missing info

Adam Moody and TorstenHoefler

Chicago 3/28/11

where is mpi info used
Where is MPI_Info used?
  • Functions that take MPI_Info
    • DIST_GRAPH_CREATE_ADJACENT, DIST_GRAPH_CREATE
    • ALLOC_MEM
    • COMM_SPAWN, COMM_SPAWN_MULTIPLE
    • OPEN_PORT, COMM_ACCEPT, COMM_CONNECT, PUBLISH_NAME, UNPUBLISH_NAME, LOOKUP_NAME
    • WIN_CREATE
    • FILE_OPEN, FILE_DELETE, FILE_SET_INFO, FILE_GET_INFO, FILE_SET_VIEW
  • Relevant sections
    • Chapter 9: Info Object
    • Section 13.2.8: File Info
    • A.1.5: Info Keys
    • A.1.6: Info Values
some hints are assertions
Some hints are assertions
  • Some MPI_Info hints are assertions; MPI can crash if app lies, e.g.,
    • no_locks– MPI can break if no_locks is specified but app uses MPI_Win_lock anyway.
  • Possible assertions for communicators
    • no_any_source– simplifies matching
    • no_any_tag – simplifies matching
    • free_strict – no reference counting
    • no_reduction_determinism – optimized colls
    • no_heterogeneity – simpler DT handling
    • no_send_cancel – simpler send handling
    • match_packed – MPI_PACKED in send only matches MPI_PACKED in recv
    • strict_topology – only send pt-2-pt to neighbors in topology
slide4

#4 is needed already – what if app sets no_locks on window and then passes window to library?

  • #2 will be needed if we ever define any assertions on comms.
  • Thoughts on #1 and #3?
discussion points
Discussion points
  • Copy info on COMM_DUP?
    • Intent of dup is to provide identical comm for library.
    • We copy attributes, topology, and error handler.
    • On other hand, this may inhibit library (e.g., strict_topology).
  • FILE_GET_INFO returns all hints in use, including those not set by user. Want to do the same for comms and windows?
  • Once set on file, hints cannot be unset, p398, line 29
    • “When an info object that specifies a subset of valid hints is passed to MPI_FILE_SET_VIEW or MPI_FILE_SET_INFO, there will be no effect on previously set or defaulted hints that the info does not specify.”
suggested proposal
Suggested proposal
  • MPI_COMM_GET_INFO
  • MPI_WIN_GET_INFO
  • MPI_COMM_SET_INFO
    • May ignore hints that otherwise can be set at creation
  • MPI_WIN_SET_INFO
    • May ignore hints that otherwise can be set at creation
  • MPI_COMM_DUP(incomm, outcomm)
    • Duplicates info from incomm
  • MPI_COMM_DUP_INFO(incomm, outcomm, info)
    • Overwrites info from incomm