3.1.5. Runtime environment variables¶
We describe the main environment variables which is specifiable when execution on Fortran/C/C++ program. The environment variables described here differ when using the LLVM OpenMP library (-Nlibomp option) and when using the Fujitsu OpenMP library (-Nfjomplib option).
Please refer to the manual “Fortran User’s Guide”, “C User’s Guide”, and “C ++ User’s Guide” for details.
Environment variables |
Description |
|---|---|
OMP_NUM_THREADS |
The number of threads to operate in parallel can be specified.
If omitted, the number of cores available for the job (48 for 1 node and 1 process) is used.
|
OMP_STACKSIZE |
The size of the stack area for each thread can be specified in bytes, K bytes, M bytes, G bytes, and T bytes. The default value is 8 Mbytes. |
Environment variables |
Description |
|---|---|
PARALLEL |
The number of threads to operate in parallel can be specified.
If omitted, the number of cores available for the job (48 for 1 process per node) is used.
When the environment variable FLIB_FASTOMP is set to TRUE (default), if the environment variable OMP_NUM_THREADS has a specified value, that value and the specified value of the environment variable PARALLEL must match.
If not matched, the smaller number of threads is used. In this case, the jwe1042i-w message is output.
|
OMP_NUM_THREADS |
The number of threads to operate in parallel can be specified.
If omitted, the number of cores available for the job (48 for 1 process per node) is used.
|
THREAD_STACK_SIZE |
The size of the stack area for each thread can be specified in Kbytes.
If the environment variable OMP_STACKSIZE is specified, the larger specified value will be the size of the stack area for each thread.
|
OMP_STACKSIZE |
The size of the stack area for each thread can be specified in bytes, K bytes, M bytes, or G bytes.
If the environment variable THREAD_STACK_SIZE is specified, the larger specified value will be the size of the stack area for each thread.
|