Intel® MPI Library

Developer Reference for Linux* OS

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ID 768732
Date 6/30/2025
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Document Table of Contents
Document Table of Contents x
Developer Reference for Linux* OS
Developer Reference for Linux* OS x
Introduction Command Reference Environment Variable Reference Miscellaneous Notices and Disclaimers
Introduction x
Introducing Intel® MPI Library Notational Conventions Related Information
Command Reference x
Compiler Commands mpirun mpiexec.hydra cpuinfo impi_info mpitune_fast
Compiler Commands x
Compilation Command Options
mpiexec.hydra x
Global Hydra Options Local Hydra Options gtool Options
Environment Variable Reference x
Compilation Environment Variables Hydra Environment Variables I_MPI_ADJUST Family Environment Variables Tuning Environment Variables Process Pinning GPU Support NIC Pinning Environment Variables for Fabrics Control Environment Variables for Memory Policy Control Environment Variables for Asynchronous Progress Control Environment Variables for Multi-EP I_MPI_THREAD_SPLIT I_MPI_THREAD_RUNTIME I_MPI_THREAD_MAX I_MPI_THREAD_ID_KEY Other Environment Variables
Hydra Environment Variables x
Environment Variables Not Propagated by Hydra
Tuning Environment Variables x
Autotuning
Autotuning x
I_MPI_TUNING_AUTO Family Environment Variables
Process Pinning x
Environment Variables for Process Pinning Interoperability with OpenMP* API
GPU Support x
GPU Pinning GPU Buffers Support
Environment Variables for Fabrics Control x
Communication Fabrics Control Shared Memory Control OFI*-capable Network Fabrics Control
Miscellaneous x
Java* Bindings for MPI-2 Routines
Developer Reference for Linux* OS

Environment Variables for Multi-EP

I_MPI_THREAD_SPLIT

Syntax

I_MPI_THREAD_SPLIT=<value>

Arguments

Value Binary Indicator
0 | no | off | disable Disable the MPI_THREAD_SPLIT model support. This is the default value.
1 | yes | on | enable Enable the MPI_THREAD_SPLIT model support.

Description

Use this environment variable to control the I_MPI_THREAD_SPLIT programming model.

For more information on MPI_THREAD_SPLIT, refer to the Intel® MPI Library Developer Guide, section MPI_THREAD_SPLIT Programming Model.

I_MPI_THREAD_RUNTIME

Syntax

I_MPI_THREAD_RUNTIME=<value>

Arguments

Value Thread Runtime
generic Enable runtime support (for example, pthreads, TBB). This is the default value if OpenMP* cannot be detected at runtime.
openmp Enable OpenMP runtime support. This is the default value if OpenMP is detected at runtime.

Description

Use this environment variable to control threading runtime support.

NOTE:
I_MPI_THREAD_SPLIT model support is enabled.

I_MPI_THREAD_MAX

Syntax

I_MPI_THREAD_MAX=<int>

Arguments

<int> The maximum number of threads per rank. The default value is omp_get_max_threads() if I_MPI_THREAD_RUNTIME is set to openmp. The value is 1 otherwise

Description

Use this environment variable to set the maximum number of threads to be used in each process concurrently.

I_MPI_THREAD_ID_KEY

Syntax

I_MPI_THREAD_ID_KEY=<string>

Arguments

<string> Define the MPI info object key. The default value is thread_id

Description

Use this environment variable to set the MPI info object key that is used to explicitly define the logical thread number thread_id.

Parent topic: Environment Variable Reference
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