modified on 30 September 2015 at 06:19 ••• 7,985 views

Release66:ARMCI

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Choosing the Right ARMCI Library

The Global Arrays parallel environment relies upon a one-sided communication runtime system. There are at least three options currently available:

  • ARMCI - This is the original one-sided library developed with Global Arrays by PNNL. It supports the widest range of platforms. See http://hpc.pnl.gov/armci/ for details.
  • ComEx - This library is being developed by PNNL to replace ARMCI. It supports the fewer platforms than ARMCI but may be more robust on modern ones like InfiniBand. See http://hpc.pnl.gov/comex/ for details.
  • ARMCI-MPI - This library is a completely separate implementation of the ARMCI interface by Argonne and Intel. It uses the one-sided communication features of MPI, rather than a platform-specific conduit. It currents provides both MPI-2 and MPI-3 implementations; the MPI-3 one is supported by nearly all platforms. See https://wiki.mpich.org/armci-mpi/index.php/Main_Page for details.

By default, Global Arrays will choose ARMCI or ComEx, based upon the environment variables selected by the user (see GA documentation for details). When a native implementation is available and works reliably, this is the best option for the NWChem user. However, in cases where an native implementation of ARMCI is not available or is not reliable, the user should consider using one of the MPI-based implementations.

There are many different ways to use MPI as the communication runtime of Global Arrays:

  • ARMCI_NETWORK=MPI-PR - ARMCI with progress rank
  • ARMCI_NETWORK=MPI-PT - ARMCI with progress thread
  • ARMCI_NETWORK=MPI-MT - ARMCI over multi-threaded MPI
  • ARMCI_NETWORK=MPI-TS - ARMCI over MPI without data server
  • ARMCI_NETWORK=MPI-SPAWN - ARMCI over MPI using MPI-Spawn to create the extra data server process
  • ARMCI_NETWORK=ARMCI and EXTERNAL_ARMCI_PATH=path-to-armci-mpi - uses ARMCI-MPI


Printable items in the TCE modules and their default print levels
Item Print Level Description
"time" vary CPU and wall times
"mo2e" debug Two-electron integral transformation