OpenMP* Environment Variables

This topic describes the OpenMP* environment variables (with the OMP_ prefix) and Intel-specific environment variables (with the KMP_ prefix).

Standard Environment Variables

Variable Description Default
OMP_SCHEDULE Sets the runtime schedule type and chunk size. STATIC ( no chunk size specified)
OMP_NUM_THREADS Sets the number of threads to use during execution. Number of processors
OMP_DYNAMIC Enables (TRUE) or disables (FALSE) the dynamic adjustment of the number of threads. FALSE
OMP_NESTED Enables (TRUE) or disables (FALSE) nested parallelism. FALSE

Intel Extension Environment Variables

Environment Variable Description Default
KMP_LIBRARY Selects the OpenMP run-time library throughput. The options for the variable value are: serial, turnaround, or throughput indicating the execution mode. The default value of throughput is used if this variable is not specified. throughput
(execution mode)
KMP_STACKSIZE Sets the number of bytes to allocate for each parallel thread to use as its private stack. Use the optional suffix b, k, m, g, or t, to specify bytes, kilobytes, megabytes, gigabytes, or terabytes. IA-32: 2m
Itanium® compiler: 4m