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Release66:ARMCI

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{| border='1' cellspacing='0'
{| border='1' cellspacing='0'
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|+Caption
 
| ARMCI_NETWORK
| ARMCI_NETWORK
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| Additional variables
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| Additional options
| Result
| Result
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| Notes
|-
|-
| MPI-PR
| MPI-PR
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| None
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|  
| ARMCI with progress rank
| ARMCI with progress rank
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| Recommended
|-
|-
| MPI-PT
| MPI-PT
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| None
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|  
| ARMCI with progress thread
| ARMCI with progress thread
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|
|-
|-
| MPI-MT
| MPI-MT
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| None
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|  
| ARMCI over multi-threaded MPI
| ARMCI over multi-threaded MPI
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| [https://github.com/open-mpi/ompi/issues/157 Do not use Open-MPI].
|-
|-
| MPI-TS
| MPI-TS
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| None
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|  
| ARMCI over MPI without data server
| ARMCI over MPI without data server
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|
|-
|-
| MPI-SPAWN
| MPI-SPAWN
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| None
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|  
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| ARMCI over MPI using MPI-Spawn to create the extra data server process
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| ARMCI over MPI using dynamic processes
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| Requires MPI_Comm_spawn support.
|-
|-
| ARMCI
| ARMCI
| EXTERNAL_ARMCI_PATH
| EXTERNAL_ARMCI_PATH
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| ARMCI-MPI
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| Uses ARMCI-MPI (please use ''mpi3rma'' branch)
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| See [https://wiki.mpich.org/armci-mpi/index.php/NWChem the ARMCI-MPI NWChem page] for details.
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Please see https://wiki.mpich.org/armci-mpi/index.php/NWChem for details on how to build NWChem with ARMCI-MPI.  This will be the location of the most complete, accurate and up-to-date information about ARMCI-MPI.
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It is difficult to provide complete guidance to the user as to which option to choose. However, it is observed that ARMCI_NETWORK=MPI-PR is stable and performs well on Cray XC platforms (e.g. NERSC Edison).  On Intel True Scale systems, MPI-MT is more reliable than OPENIB or MPI-SPAWN. On IBM Blue Gene/Q, one must use the ''mpi2rma'' branch of ARMCI-MPI because MPI-3 is not fully supportedOn all other platforms, the ARMCI-MPI branch ''mpi3rma'' is recommended.  Please make sure to use the most recent version of MPI when using ARMCI-MPI.

Revision as of 07:41, 30 September 2015

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 Additional options Result Notes
MPI-PR ARMCI with progress rank Recommended
MPI-PT ARMCI with progress thread
MPI-MT ARMCI over multi-threaded MPI Do not use Open-MPI.
MPI-TS ARMCI over MPI without data server
MPI-SPAWN ARMCI over MPI using dynamic processes Requires MPI_Comm_spawn support.
ARMCI EXTERNAL_ARMCI_PATH Uses ARMCI-MPI (please use mpi3rma branch) See the ARMCI-MPI NWChem page for details.

It is difficult to provide complete guidance to the user as to which option to choose. However, it is observed that ARMCI_NETWORK=MPI-PR is stable and performs well on Cray XC platforms (e.g. NERSC Edison). On Intel True Scale systems, MPI-MT is more reliable than OPENIB or MPI-SPAWN. On IBM Blue Gene/Q, one must use the mpi2rma branch of ARMCI-MPI because MPI-3 is not fully supported. On all other platforms, the ARMCI-MPI branch mpi3rma is recommended. Please make sure to use the most recent version of MPI when using ARMCI-MPI.