Library Constants

ISHMEM_MAJOR_VERSION

Integer representing the major version of Intel® SHMEM Specification in use.

ISHMEM_MINOR_VERSION

Integer representing the minor version of Intel® SHMEM Specification in use.

ISHMEM_MAX_NAME_LEN

Integer representing the maximum length of ISHMEM_VENDOR_STRING.

ISHMEM_VENDOR_STRING

String representing vendor defined information of size at most ISHMEM_MAX_NAME_LEN. The string ISHMEM_VENDOR_STRING is terminated by a null character.

Environment Variables

The Intel® SHMEM specification provides a set of environment variables that allows users to configure the implementation and receive information about the implementation.

ISHMEM_VERSION

If set to any value, print the library version at startup.

ISHMEM_INFO

If set to any value, print helpful text about all these environment variables.

ISHMEM_SYMMETRIC_SIZE

Specifies the size (in bytes) of the symmetric heap memory per PE. The resulting size is implementation-defined and must be at 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 \(2^{10}\) (kibibytes)

• m or M multiplies by \(2^{20}\) (mebibytes)

• g or G multiplies by \(2^{30}\) (gibibytes)

• t or T multiplies by \(2^{40}\) (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 ISHMEM_SYMMETRIC_SIZE is an error, which causes the Intel® SHMEM library to terminate the program.

ISHMEM_DEBUG

If set to any value, enable debugging messages.

ISHMEM_SHMEM_LIB_NAME

Informs the Intel® SHMEM library of the shared object name (e.g. libshmem.so) of the host-side OpenSHMEM library to be dynamically loaded. The default value is libsma.so.

ISHMEM_ENABLE_GPU_IPC

Enables the intra-node inter-process communication (IPC) implementation. The default value is 1 which enables use of the Intel® \(\text{X}^e\) Link fabric for inter-GPU communications on the same super-node. The value can be set to 0 for situations in which Intel® \(\text{X}^e\) Link fabric is not available or does not connect all the GPUs.

ISHMEM_ENABLE_GPU_IPC_PIDFD

Enables the pidfd implementation of IPC. This is enabled by default, but will fail on older Linux kernels that do not support the necessary systiem calls. In such cases, use ISHMEM_ENABLE_GPU_IPC_PIDFD=0

ISHMEM_ENABLE_ACCESSIBLE_HOST_HEAP

Place symmetric heap in host unified shared memory (allocated on the host and accessible by the host and device).