User`s guide

Intel® MPI Library User’s Guide for Windows* OS

2.6. Selecting a Network Fabric

The Intel® MPI Library dynamically selects different fabrics for communication between MPI

processes. To select a specific fabric combination, set the I_MPI_FABRICS environment variable.

2.6.1. I_MPI_FABRICS

Select a particular network fabric to be used for communication.

Syntax

I_MPI_FABRICS=<fabric>|<intra-node fabric>:<inter-nodes fabric>

Where

 <fabric> := {shm, dapl, tcp}

 <intra-node fabric> := {shm, dapl, tcp}

 <inter-nodes fabric> := {dapl,tcp}

Arguments

Argument

Definition

Define a network fabric

shm

Shared-memory

dapl

DAPL-capable network fabrics, such as InfiniBand*, iWarp*,

Dolphin*, and XPMEM* (through DAPL*)

tcp

TCP/IP-capable network fabrics, such as Ethernet and

InfiniBand* (through IPoIB*)

For example, to select the OFED* InfiniBand* device, use the following command:

> mpiexec.hydra -n <# of processes> \

-env I_MPI_FABRICS shm:dapl <executable>

For these devices, if <provider> is not specified, the first DAPL* provider in the dat.conf file is

used. The shm fabric is available for both Intel® and non-Intel microprocessors, but it may

perform additional optimizations for Intel microprocessors than it performs for non-Intel

microprocessors.

NOTE

Ensure the selected fabric is available. For example, use shm only if all the processes can

communicate with each other through shared memory. Use dapl only if all the processes can

communicate with each other through a single DAPL provider. Ensure that the dat.dll library

is in your %PATH%. Otherwise, use the -genv option for mpiexec.exe for setting the

I_MPI_DAT_LIBRARY environment variable with the fully-qualified path to the dat.dll library.