Developer Reference

Other Environment Variables

I_MPI_DEBUG

Print out debugging information when an MPI program starts running.
Syntax
I_MPI_DEBUG=
<level>
[,<flags>]
Arguments
<level>
Indicate the level of debug information provided.
0
Output no debugging information. This is the default value.
1
Output libfabric* version and provider.
2
Output information about the tuning file used.
3
Output effective MPI rank,
pid
and node mapping table.
4
Output process pinning information.
5
Output environment variables specific to the Intel® MPI Library.
> 5
Add extra levels of debug information.
<flags>
Comma-separated list of debug flags
pid
Show process id for each debug message.
tid
Show thread id for each debug message for multithreaded library.
time
Show time for each debug message.
datetime
Show time and date for each debug message.
host
Show host name for each debug message.
level
Show level for each debug message.
scope
Show scope for each debug message.
line
Show source line number for each debug message.
file
Show source file name for each debug message.
nofunc
Do not show routine name.
norank
Do not show rank.
nousrwarn
Suppress warnings for improper use case (for example, incompatible combination of controls).
flock
Synchronize debug output from different process or threads.
nobuf
Do not use buffered I/O for debug output.
Description
Set this environment variable to print debugging information about the application.
Set the same
<
level
>
value for all ranks.
You can specify the output file name for debug information by setting the
I_MPI_DEBUG_OUTPUT
environment variable.
Each printed line has the following format:
[<
identifier
>] <
message
>
where:
  • <
    identifier
    >
    is the MPI process rank, by default. If you add the '
    +
    ' sign in front of the
    <
    level
    >
    number, the
    <
    identifier
    >
    assumes the following format:
    rank#pid@hostname
    . Here,
    rank
    is the MPI process rank,
    pid
    is the process ID, and
    hostname
    is the host name. If you add the '
    -
    ' sign,
    <
    identifier
    >
    is not printed at all.
  • <
    message
    >
    contains the debugging output.
The following examples demonstrate possible command lines with the corresponding output:
> mpiexec -n 1 -env I_MPI_DEBUG=2 test.exe ... [0] MPI startup(): shared memory data transfer mode
The following commands are equal and produce the same output:
> mpiexec -n 1 -env I_MPI_DEBUG=2,pid,host test.exe ... [0#1986@mpicluster001] MPI startup(): shared memory data transfer mode
Compiling with the
/Zi
,
/ZI
,
or
/Z7
option adds a considerable amount of printed debug information.

I_MPI_DEBUG_OUTPUT

Set output file name for debug information.
Syntax
I_MPI_DEBUG_OUTPUT=
<arg>
Arguments
Argument
String Value
stdout
Output to
stdout
. This is the default value.
stderr
Output to
stderr.
<file_name>
Specify the output file name for debug information (the maximum file name length is 256 symbols).
Description
Set this environment variable if you want to split output of debug information from the output produced by an application. If you use format like
%r
,
%p
or
%h
, rank, process ID or host name is added to the file name accordingly.

I_MPI_DEBUG_COREDUMP

Controls core dump files generation in case of failure during MPI application execution.
Syntax
I_MPI_DEBUG_COREDUMP=
<arg>
Arguments
Argument
Binary Indicator
enable|yes|on|1
Enable coredump files generation.
disable|no|off|0
Do not generate coredump files. Default value.
Description
Set this environment variable to enable coredump files dumping in case of termination caused by segmentation fault. Available for both release and debug builds.

I_MPI_PMI_VALUE_LENGTH_MAX

Control the length of the value buffer in PMI on the client side.
Syntax
I_MPI_PMI_VALUE_LENGTH_MAX=<
length
>
Arguments
<
length
>
Define the value of the buffer length in bytes.
<
n
> > 0
 The default value is -1, which means do not override the value received from the
PMI_KVS_Get_value_length_max()
function.
Description
Set this environment variable to control the length of the value buffer in PMI on the client side. The length of the buffer will be the lesser of
I_MPI_PMI_VALUE_LENGTH_MAX
and
PMI_KVS_Get_value_length_max()
.

I_MPI_REMOVED_VAR_WARNING

Print out a warning if a removed environment variable is set.
Syntax
I_MPI_REMOVED_VAR_WARNING=
<arg>
Arguments
Argument
Binary Indicator
enable | yes | on | 1
Print out the warning. This is the default value
disable | no | off | 0
Do not print the warning
Description
Use this environment variable to print out a warning if a removed environment variable is set. Warnings are printed regardless of whether
I_MPI_DEBUG is set.

I_MPI_VAR_CHECK_SPELLING

Print out a warning if an unknown environment variable is set.
Syntax
I_MPI_VAR_CHECK_SPELLING=
<arg>
Arguments
Argument
Binary Indicator
enable | yes | on | 1
Print out the warning. This is the default value
disable | no | off | 0
Do not print the warning
Description
Use this environment variable to print out a warning if an unsupported environment variable is set. Warnings are printed in case of removed or misprinted environment variables.

I_MPI_LIBRARY_KIND

Specify the Intel® MPI Library configuration.
Syntax
I_MPI_LIBRARY_KIND=
<value>
Arguments
Value
Description
release
Multi-threaded optimized library. This is the default value
debug
Multi-threaded debug library
Description
Use this variable to set an argument for the
vars.
bat
script. This script establishes the Intel® MPI Library environment and enables you to specify the appropriate library configuration. To ensure that the desired configuration is set, check the
LD_LIBRARY_PATH
variable.
Example
> export I_MPI_LIBRARY_KIND=debug
Setting this variable is equivalent to passing an argument directly to the
vars.[c]sh
script:
Example
> <installdir> \env\vars.bat release

I_MPI_PLATFORM

Select the intended optimization platform.
Syntax
I_MPI_PLATFORM=
<platform>
Arguments
<platform>
Intended optimization platform (string value)
auto
Use only with heterogeneous runs to determine the appropriate platform across all nodes. May slow down MPI initialization time due to collective operation across all nodes.
ivb
Optimize for the Intel® Xeon® Processors E3, E5, and E7 V2 series and other Intel® Architecture processors formerly code named Ivy Bridge.
hsw
Optimize for the Intel Xeon Processors E3, E5, and E7 V3 series and other Intel® Architecture processors formerly code named Haswell.
bdw
Optimize for the Intel Xeon Processors E3, E5, and E7 V4 series and other Intel Architecture processors formerly code named Broadwell.
knl
Optimize for the Intel® Xeon Phi™ processor and coprocessor formerly code named Knights Landing.
skx
Optimize for the Intel Xeon Processors E3 V5 and Intel Xeon Scalable Family series, and other Intel Architecture processors formerly code named Skylake.
clx
Optimize for the 2nd Generation Intel Xeon Scalable Processors, and other Intel® Architecture processors formerly code named Cascade Lake.
clx-ap
Optimize for the 2nd Generation Intel Xeon Scalable Processors, and other Intel Architecture processors formerly code named Cascade Lake AP
Note:
The explicit
clx-ap
setting is ignored if the actual platform is not Intel.
Description
Set this environment variable to use the predefined platform settings. The default value is a local platform for each node.
The variable is available for both Intel and non-Intel microprocessors, but it may utilize additional optimizations for Intel microprocessors than it utilizes for non-Intel microprocessors.
The values
auto[:min]
,
auto:max
, and
auto:most
may increase the MPI job startup time.

I_MPI_MALLOC

Control the Intel® MPI Library custom allocator of private memory.
Syntax
I_MPI_MALLOC=
<arg>
Argument
Argument
Binary Indicator
1
Enable the Intel MPI Library custom allocator of private memory.
Use the Intel MPI custom allocator of private memory for
MPI_Alloc_mem/MPI_Free_mem
.
0
Disable the Intel MPI Library custom allocator of private memory.
Use the system-provided memory allocator for
MPI_Alloc_mem/MPI_Free_mem
.
Description
Use this environment variable to enable or disable the Intel MPI Library custom allocator of private memory for
MPI_Alloc_mem/MPI_Free_mem
.
By default,
I_MPI_MALLOC
is enabled if
I_MPI_ASYNC_PROGRESS
and
I_MPI_THREAD_SPLIT
are disabled.
If the platform is not supported by the Intel MPI Library custom allocator of private memory, a system-provided memory allocator is used and the
I_MPI_MALLOC
variable is ignored.

I_MPI_WAIT_MODE

Control the Intel® MPI Library optimization for oversubscription mode.
Syntax
I_MPI_WAIT_MODE=
<arg>
Arguments
Argument
Binary Indicator
0
Optimize MPI application to work in the normal mode (1 rank on 1 CPU). This is the default value if the number of processes on a computation node is less than or equal to the number of CPUs on the node.
1
Optimize MPI application to work in the oversubscription mode (multiple ranks on 1 CPU). This is the default value if the number of processes on a computation node is greater than the number of CPUs on the node.
Description
It is recommended to use this variable in the oversubscription mode.

I_MPI_THREAD_YIELD

Control the Intel® MPI Library thread yield customization during MPI busy wait time.
Syntax
I_MPI_THREAD_YIELD=
<arg>
Arguments
Argument
Description
0
Do nothing for thread yield during the busy wait (spin wait). This is the default value when
I_MPI_WAIT_MODE=0
1
Do the
pause processor
instruction for
I_MPI_PAUSE_COUNT
during the busy wait.
2
Do the
SwitchToThread()
system call for thread yield during the busy wait.
This is the default value when
I_MPI_WAIT_MODE=1
3
Do the
Sleep()
system call for
I_MPI_THREAD_SLEEP
number of milliseconds for thread yield during the busy wait.
Description
I_MPI_THREAD_YIELD=0
or
I_MPI_THREAD_YIELD=1
in the normal mode and
I_MPI_THREAD_YIELD=2
or
I_MPI_THREAD_YIELD=3
in the oversubscription mode.

I_MPI_PAUSE_COUNT

Control the Intel® MPI Library pause count for the thread yield customization during MPI busy wait time.
Syntax
I_MPI_PAUSE_COUNT=
<arg>
Argument
Argument
Description
>=0
Pause count for thread yield customization during MPI busy wait time.
The default value is 0. Normally, the value is less than 100.
Description
This variable is applicable when
I_MPI_THREAD_YIELD=1
. Small values of
I_MPI_PAUSE_COUNT
may increase performance, while larger values may reduce energy consumption.

I_MPI_SPIN_COUNT

Control the spin count value.
Syntax
I_MPI_SPIN_COUNT=
<scount>
Argument
<scount>
Define the loop spin count when polling fabric(s).
>=0
The default <scount> value is equal to 1 when more than one process runs per processor/core. Otherwise the value equals 2000. The maximum value is equal to 2147483647.
Description
Set the spin count limit. The loop for polling the fabric(s) spins
<scount>
times before the library releases the processes if no incoming messages are received for processing. Smaller values for
<scount>
cause the Intel® MPI Library to release the processor more frequently.
Use the
I_MPI_SPIN_COUNT
environment variable for tuning application performance. The best value for
<scount>
can be chosen on an experimental basis. It depends on the particular computational environment and application.

I_MPI_THREAD_SLEEP

Control the Intel® MPI Library thread sleep
milliseconds
timeout for thread yield customization while MPI busy wait progress.
Syntax
I_MPI_THREAD_SLEEP=
<arg>
Argument
Argument
Description
>=0
Thread sleep microseconds timeout. The default value is 0. Normally, the value is less than 100.
Description
This variable is applicable when
I_MPI_THREAD_YIELD=3
. Small values of
I_MPI_PAUSE_COUNT
may increase performance in the normal mode, while larger values may increase performance in the oversubscription mode

I_MPI_EXTRA_FILESYSTEM

Control native support for parallel file systems.
Syntax
I_MPI_EXTRA_FILESYSTEM=
<arg>
Argument
Argument
Binary Indicator
enable | yes | on | 1
Enable native support for parallel file systems.
disable | no | off | 0
Disable native support for parallel file systems. This is the default value.
Description
Use this environment variable to enable or disable native support for parallel file systems.

I_MPI_EXTRA_FILESYSTEM_FORCE

Syntax
I_MPI_EXTRA_FILESYSTEM_FORCE=<ufs|nfs|gpfs|panfs|lustre>
Description
Force filesystem recognition logic. Setting this variable is equivalent to prefixing all paths in MPI-IO calls with the selected filesystem plus colon.

I_MPI_MULTIRAIL

Syntax
I_MPI_MULTIRAIL=
<arg>
Argument
Argument
Binary Indicator
1
Enable multi-rail capability.
0
Disable multi-rail capability. This is the default value.
Description
Set this variable to enable multi-rail capability and identify NICs serviced by the provider. Pick this variable on the same NUMA.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.