.. _subsec:environment_variables:

Environment Variables
=====================

NVSHMEM provides a set of environment variables that allows users to
configure the NVSHMEM implementation and receive information about the
implementation.

.. c:var:: NVSHMEM_VERSION

*Value*: Any

Print the library version at start-up

.. c:var:: NVSHMEM_INFO

*Value*: Any

Print helpful text about all these environment variables

.. c:var:: NVSHMEM_SYMMETRIC_SIZE

*Value*: Non-negative integer or floating point value with an optional
character suffix

Specifies the size (in bytes) of the symmetric heap memory per PE. The
resulting size is implementation-defined and must be least as large as
the integer ceiling of the product of the numeric prefix and the scaling
factor. The allowed character suffixes for the scaling factor are as
follows:

-  k or K multiplies by :math:`2^{10}` (kibibytes)

-  m or M multiplies by :math:`2^{20}` (mebibytes)

-  g or G multiplies by :math:`2^{30}` (gibibytes)

-  t or T multiplies by :math:`2^{40}` (tebibytes)

For example, string “20m” is equivalent to the integer value 20971520,
or 20 mebibytes. Similarly the string “3.1M” is equivalent to the
integer value 3250586. Only one multiplier is recognized and any
characters following the multiplier are ignored, so “20kk” will not
produce the same result as “20m”. Usage of string “.5m” will yield the
same result as the string “0.5m”.

An invalid value for ``NVSHMEM_SYMMETRIC_SIZE`` is an error, which the
NVSHMEM library shall report by either returning a nonzero value from
``nvshmem_init_thread`` or causing program termination.

.. include:: ../env-nvshmem.in